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White-Light and Lyman-alpha Emissions in Solar Flares: Timing, Timescale, Energy, and Scaling

2026-06-03T20:57:02Z

Hhudson: 528 initial

{{Infobox Nugget |name = Nugget
|title = White-Light and Lyman-alpha Emissions in Solar Flares: Timing, Timescale, Energy, and Scaling
|number = 528
|first_author = Dechao SONG et al.
|publish_date = June 8, 2026
|next_nugget = TBD
|previous_nugget = {{#ask: [[Category:Nugget]] [[RHESSI Nugget Index::527]]}}
}}

== Introduction ==

Solar flares are among the most energetic eruptive phenomena in the
solar system, producing enhanced radiation across nearly the entire
electromagnetic spectrum. Among flare emissions, white-light (WL)
continuum and hydrogen Lyα emission at 1216 Å provide particularly
important diagnostics of energy deposition in the lower solar
atmosphere. White-light flares (WLFs) are intense brightenings in
the WL continuum, indicating substantial energy deposition in the
lower chromosphere and possibly even deeper layers. Lyα, the strongest
line in the solar vacuum ultraviolet spectrum, traces the chromospheric
and transition-region response. Although WL and Lyα emissions are
thought to share a common flare-energy driver, their relationship
remains poorly understood. In this Nugget, we present a statistical
study of 69 WLFs observed during 2010-2015 (Figure 1), combining
GOES Lyα and SXR irradiance with WL continuum intensity near 6173 Å
from SDO/HMI (Ref. [1]).

[[File:528f1.png|center|thumb|450px|caption|Figure 1: 
Spatial distribution of the 69 WLFs on the solar disk. The sample includes 22 X-class (magenta), 44 M-class (cyan), and 3 C-class (gray) flares.
]]

== Stronger Lyα Enhancement in WLFs ==

We define the Lyα contrast as
(Fpeak-Fbkg)/Fbkg x 100%.
For our 69 WLFs, this contrast ranges from 0.8% to 28.5% (mean 7.0%), with a
95th percentile (P95) of ~20%. In comparison Ref. [2]) reported a P95 of
only ~10% for 477 M- and X-class flares
not restricted to WLFs, indicating that WLFs produce a notably
stronger Lyα respone.

== Peak-time Ordering: A Nonthermal Imprint ==

For most WLFs, the Lyα peak is nearly cotemporal with the SXR
time-derivative peak - a hallmark of the
[https://heliowiki.smce.nasa.gov/wiki/index.php/The_Neupert_Effect_Revisited Neupert effect] - underscoring
the nonthermal origin of flare Lyα emission (Figure 2 (b)). The WL
peak is cotemporal with or slightly lags the Lyα and SXR derivative
peaks by a median of ~30-40 s (Figures 2 (a) and (c)), likely due
to hydrogen recombination and/or radiative backwarming processes.

[[File:528f2.png|center|thumb|500px|caption|Figure 2: 
Distributions of the peak-time differences among Ly, WL, and the
SXR time derivative, highlighting the temporal ordering of
impulsive-phase emissions. The green background is the uncertainty
introduced by the different temporal resolutions of the observations.
]]

== Correlated Rise Phases and Timescale Comparisons ==

The Lyα and WL emissions exhibit positive power-law correlations in
rise time
([https://en.wikipedia.org/wiki/Kendall_rank_correlation_coefficient Kendall's tau correlation coefficient (KCC)] = 0.41),
and in the peak-enhancement growth rate
Fpeak-Fbkg)/trise, KCC = 0.49),
with remarkably similar rise times of ~34 minutes, suggesting
a common impulsive driver.
However, their decay times (e-folding)
and durations (rise plus decay times) show only low-to-medium
correlations (KCCs < 0.34), indicating distinct post-peak cooling
mechanisms.

== Radiated Energy: What Shapes It? ==

For the Lyα band, all four parameters peak enhancement, rise time,
decay time, and duration - exhibit positive power-law correlations
with Lyα energy (KCCs 0.40), with the strongest dependencies on the decay
time and duration (KCCs 0.53), implying that the Lyα energy budget
accumulates significantly during the gradual phase (Figure 3).

[[File:528f3.png|center|thumb|700px|caption|Figure 3: 
Relationships of the radiated energy with the peak enhancement,
rise time, decay time, and duration for the Lyα (top) and WL (bottom)
bands.
]]

In contrast, WL energy shows the strongest correlation with its peak
enhancement (KCC = 0.67), whereas its correlations with the rise
time, decay time, and duration are all weaker. This indicates that
it is more closely associated with the magnitude of the impulsive
peak enhancement than with flare timescales.
The WL energy-duration
relation τ ~ E0.32 ± 0.06 closely matches the
theoretical value 1/3
predicted by simplified magnetic reconnection models and is comparable
to values found for stellar superflares
(Ref. [3]), consistent with a common reconnection-driven
scaling across solar and stellar flare energy ranges.

== Conclusions and Outlook ==

We have established quantitative power-law scaling relationships
between Lyα and WL emissions for 69 solar WLFs. These empirical solar
scaling laws provide a useful bridge for estimating the Ly emission
properties of solar-like stellar flares from routinely observed WL
emissions. We also note that HMI's narrowband pseudocontinuum near
6173 Å differs from broadband stellar photometry, which introduces
some limitations.

== Acknowledgments ==

Ying LI, Qiao Li, and Xiaofeng LIU are co-authors of this Nugget and of
Ref. [1].

== References ==

[1] [https://ui.adsabs.harvard.edu/abs/2026ApJ..1001..195S/abstract "The Lyα Emission in Solar Flares. II. A Statistical Study on Its Relationship with the White-light plus Soft X-Ray Emission"]

[2] [https://ui.adsabs.harvard.edu/abs/2020SpWea..1802331M/abstract "Lyman-alpha Variability During Solar Flares Over Solar Cycle 24 Using GOES-15/EUVS-E"]

[3] [https://ui.adsabs.harvard.edu/abs/2021MNRAS.505L..79Y/abstract "Statistical Studies of Solar White-light Flares and Comparisons with Superflares on Solar-type Stars"]

White-Light and Lyman-alpha Emissions in Solar Flares: Timing, Timescale, Energy, and Scaling

2026-06-03T20:54:46Z

Hhudson: /* Introduction */

{{Infobox Nugget |name = Nugget
|title = White-Light and Lyman-alpha Emissions in Solar Flares: Timing, Timescale, Energy, and Scaling
|number = 528
|first_author = Dechao SONG et al.
|publish_date = June 8, 2026
|next_nugget = TBD
|previous_nugget = {{#ask: [[Category:Nugget]] [[RHESSI Nugget Index::527]]}}
}}

== Introduction ==

Solar flares are among the most energetic eruptive phenomena in the
solar system, producing enhanced radiation across nearly the entire
electromagnetic spectrum. Among flare emissions, white-light (WL)
continuum and hydrogen Lyα emission at 1216 Å provide particularly
important diagnostics of energy deposition in the lower solar
atmosphere. White-light flares (WLFs) are intense brightenings in
the WL continuum, indicating substantial energy deposition in the
lower chromosphere and possibly even deeper layers. Lyα, the strongest
line in the solar vacuum ultraviolet spectrum, traces the chromospheric
and transition-region response. Although WL and Lyα emissions are
thought to share a common flare-energy driver, their relationship
remains poorly understood. In this Nugget, we present a statistical
study of 69 WLFs observed during 2010-2015 (Figure 1), combining
GOES Lyα and SXR irradiance with WL continuum intensity near 6173 Å
from SDO/HMI (Ref. [1]).

[[File:528f1.png|center|thumb|600px|caption|Figure 1: 
Spatial distribution of the 69 WLFs on the solar disk. The sample includes 22 X-class (magenta), 44 M-class (cyan), and 3 C-class (gray) flares.
]]

== Stronger Lyα Enhancement in WLFs ==

We define the Lyα contrast as
(Fpeak-Fbkg)/Fbkg x 100%.
For our 69 WLFs, this contrast ranges from 0.8% to 28.5% (mean 7.0%), with a
95th percentile (P95) of ~20%. In comparison Ref. [2]) reported a P95 of
only ~10% for 477 M- and X-class flares
not restricted to WLFs, indicating that WLFs produce a notably
stronger Lyα respone.

== Peak-time Ordering: A Nonthermal Imprint ==

For most WLFs, the Lyα peak is nearly cotemporal with the SXR
time-derivative peak - a hallmark of the
[https://heliowiki.smce.nasa.gov/wiki/index.php/The_Neupert_Effect_Revisited Neupert effect] - underscoring
the nonthermal origin of flare Lyα emission (Figure 2 (b)). The WL
peak is cotemporal with or slightly lags the Lyα and SXR derivative
peaks by a median of ~30-40 s (Figures 2 (a) and (c)), likely due
to hydrogen recombination and/or radiative backwarming processes.

[[File:528f2.png|center|thumb|600px|caption|Figure 2: 
Distributions of the peak-time differences among Ly, WL, and the
SXR time derivative, highlighting the temporal ordering of
impulsive-phase emissions. The green background is the uncertainty
introduced by the different temporal resolutions of the observations.
]]

== Correlated Rise Phases and Timescale Comparisons ==

The Lyα and WL emissions exhibit positive power-law correlations in
rise time
([https://en.wikipedia.org/wiki/Kendall_rank_correlation_coefficient Kendall's tau correlation coefficient (KCC)] = 0.41),
and in the peak-enhancement growth rate
Fpeak-Fbkg)/trise, KCC = 0.49),
with remarkably similar rise times of ~34 minutes, suggesting
a common impulsive driver.
However, their decay times (e-folding)
and durations (rise plus decay times) show only low-to-medium
correlations (KCCs < 0.34), indicating distinct post-peak cooling
mechanisms.

== Radiated Energy: What Shapes It? ==

For the Lyα band, all four parameters peak enhancement, rise time,
decay time, and duration - exhibit positive power-law correlations
with Lyα energy (KCCs 0.40), with the strongest dependencies on the decay
time and duration (KCCs 0.53), implying that the Lyα energy budget
accumulates significantly during the gradual phase (Figure 3).

[[File:528f3.png|center|thumb|600px|caption|Figure 3: 
Relationships of the radiated energy with the peak enhancement,
rise time, decay time, and duration for the Lyα (top) and WL (bottom)
bands.
]]

In contrast, WL energy shows the strongest correlation with its peak
enhancement (KCC = 0.67), whereas its correlations with the rise
time, decay time, and duration are all weaker. This indicates that
it is more closely associated with the magnitude of the impulsive
peak enhancement than with flare timescales.
The WL energy-duration
relation τ ~ E0.32 ± 0.06 closely matches the
theoretical value 1/3
predicted by simplified magnetic reconnection models and is comparable
to values found for stellar superflares
(Ref. [3]), consistent with a common reconnection-driven
scaling across solar and stellar flare energy ranges.

== Conclusions and Outlook ==

We have established quantitative power-law scaling relationships
between Lyα and WL emissions for 69 solar WLFs. These empirical solar
scaling laws provide a useful bridge for estimating the Ly emission
properties of solar-like stellar flares from routinely observed WL
emissions. We also note that HMI's narrowband pseudocontinuum near
6173 Å differs from broadband stellar photometry, which introduces
some limitations.

== Acknowledgments ==

Ying LI, Qiao Li, and Xiaofeng LIU are co-authors of this Nugget and of
Ref. [1].

== References ==

[1] [https://ui.adsabs.harvard.edu/abs/2026ApJ..1001..195S/abstract "The Lyα Emission in Solar Flares. II. A Statistical Study on Its Relationship with the White-light plus Soft X-Ray Emission"]

[2] [https://ui.adsabs.harvard.edu/abs/2020SpWea..1802331M/abstract "Lyman-alpha Variability During Solar Flares Over Solar Cycle 24 Using GOES-15/EUVS-E"]

[3] [https://ui.adsabs.harvard.edu/abs/2021MNRAS.505L..79Y/abstract "Statistical Studies of Solar White-light Flares and Comparisons with Superflares on Solar-type Stars"]

White-Light and Lyman-alpha Emissions in Solar Flares: Timing, Timescale, Energy, and Scaling

2026-06-03T20:53:39Z

Hhudson: No. 528 initial

{{Infobox Nugget |name = Nugget
|title = White-Light and Lyman-alpha Emissions in Solar Flares: Timing, Timescale, Energy, and Scaling
|number = 528
|first_author = Dechao SONG et al.
|publish_date = June 8, 2026
|next_nugget = TBD
|previous_nugget = {{#ask: [[Category:Nugget]] [[RHESSI Nugget Index::527]]}}
}}

== Introduction ==

Solar flares are among the most energetic eruptive phenomena in the
solar system, producing enhanced radiation across nearly the entire
electromagnetic spectrum. Among flare emissions, white-light (WL)
continuum and hydrogen Lyα emission at 1216 Å provide particularly
important diagnostics of energy deposition in the lower solar
atmosphere. White-light flares (WLFs) are intense brightenings in
the WL continuum, indicating substantial energy deposition in the
lower chromosphere and possibly even deeper layers. Ly&alpha, the strongest
line in the solar vacuum ultraviolet spectrum, traces the chromospheric
and transition-region response. Although WL and Lyα emissions are
thought to share a common flare-energy driver, their relationship
remains poorly understood. In this Nugget, we present a statistical
study of 69 WLFs observed during 2010-2015 (Figure 1), combining
GOES Lyα and SXR irradiance with WL continuum intensity near 6173 Å
from SDO/HMI (Ref. [1]).

[[File:528f1.png|center|thumb|600px|caption|Figure 1: 
Spatial distribution of the 69 WLFs on the solar disk. The sample includes 22 X-class (magenta), 44 M-class (cyan), and 3 C-class (gray) flares.
]]

== Stronger Lyα Enhancement in WLFs ==

We define the Lyα contrast as
(Fpeak-Fbkg)/Fbkg x 100%.
For our 69 WLFs, this contrast ranges from 0.8% to 28.5% (mean 7.0%), with a
95th percentile (P95) of ~20%. In comparison Ref. [2]) reported a P95 of
only ~10% for 477 M- and X-class flares
not restricted to WLFs, indicating that WLFs produce a notably
stronger Lyα respone.

== Peak-time Ordering: A Nonthermal Imprint ==

For most WLFs, the Lyα peak is nearly cotemporal with the SXR
time-derivative peak - a hallmark of the
[https://heliowiki.smce.nasa.gov/wiki/index.php/The_Neupert_Effect_Revisited Neupert effect] - underscoring
the nonthermal origin of flare Lyα emission (Figure 2 (b)). The WL
peak is cotemporal with or slightly lags the Lyα and SXR derivative
peaks by a median of ~30-40 s (Figures 2 (a) and (c)), likely due
to hydrogen recombination and/or radiative backwarming processes.

[[File:528f2.png|center|thumb|600px|caption|Figure 2: 
Distributions of the peak-time differences among Ly, WL, and the
SXR time derivative, highlighting the temporal ordering of
impulsive-phase emissions. The green background is the uncertainty
introduced by the different temporal resolutions of the observations.
]]

== Correlated Rise Phases and Timescale Comparisons ==

The Lyα and WL emissions exhibit positive power-law correlations in
rise time
([https://en.wikipedia.org/wiki/Kendall_rank_correlation_coefficient Kendall's tau correlation coefficient (KCC)] = 0.41),
and in the peak-enhancement growth rate
Fpeak-Fbkg)/trise, KCC = 0.49),
with remarkably similar rise times of ~34 minutes, suggesting
a common impulsive driver.
However, their decay times (e-folding)
and durations (rise plus decay times) show only low-to-medium
correlations (KCCs < 0.34), indicating distinct post-peak cooling
mechanisms.

== Radiated Energy: What Shapes It? ==

For the Lyα band, all four parameters peak enhancement, rise time,
decay time, and duration - exhibit positive power-law correlations
with Lyα energy (KCCs 0.40), with the strongest dependencies on the decay
time and duration (KCCs 0.53), implying that the Lyα energy budget
accumulates significantly during the gradual phase (Figure 3).

[[File:528f3.png|center|thumb|600px|caption|Figure 3: 
Relationships of the radiated energy with the peak enhancement,
rise time, decay time, and duration for the Lyα (top) and WL (bottom)
bands.
]]

In contrast, WL energy shows the strongest correlation with its peak
enhancement (KCC = 0.67), whereas its correlations with the rise
time, decay time, and duration are all weaker. This indicates that
it is more closely associated with the magnitude of the impulsive
peak enhancement than with flare timescales.
The WL energy-duration
relation τ ~ E0.32 ± 0.06 closely matches the
theoretical value 1/3
predicted by simplified magnetic reconnection models and is comparable
to values found for stellar superflares
(Ref. [3]), consistent with a common reconnection-driven
scaling across solar and stellar flare energy ranges.

== Conclusions and Outlook ==

We have established quantitative power-law scaling relationships
between Lyα and WL emissions for 69 solar WLFs. These empirical solar
scaling laws provide a useful bridge for estimating the Ly emission
properties of solar-like stellar flares from routinely observed WL
emissions. We also note that HMI's narrowband pseudocontinuum near
6173 Å differs from broadband stellar photometry, which introduces
some limitations.

== Acknowledgments ==

Ying LI, Qiao Li, and Xiaofeng LIU are co-authors of this Nugget and of
Ref. [1].

== References ==

[1] [https://ui.adsabs.harvard.edu/abs/2026ApJ..1001..195S/abstract "The Lyα Emission in Solar Flares. II. A Statistical Study on Its Relationship with the White-light plus Soft X-Ray Emission"]

[2] [https://ui.adsabs.harvard.edu/abs/2020SpWea..1802331M/abstract "Lyman-alpha Variability During Solar Flares Over Solar Cycle 24 Using GOES-15/EUVS-E"]

[3] [https://ui.adsabs.harvard.edu/abs/2021MNRAS.505L..79Y/abstract "Statistical Studies of Solar White-light Flares and Comparisons with Superflares on Solar-type Stars"]

File:528f3.png

2026-06-03T20:52:41Z

Hhudson:

File:528f2.png

2026-06-03T20:49:34Z

Hhudson: Hhudson uploaded a new version of File:528f2.png

File:528f2.png

2026-06-03T20:46:37Z

Hhudson:

File:528f1.png

2026-06-03T20:46:03Z

Hhudson:

X-ray Log Letters

2026-05-26T11:07:39Z

Hhudson: added Ack

{{Infobox Nugget |name = Nugget
|title = X-ray Log Letters
|number = 526
|first_author = Hugh HUDSON and
|second_author = Ed CLIVER
|publish_date = May 18, 2026
|next_nugget = TBD
|previous_nugget = {{#ask: [[Category:Nugget]] [[RHESSI Nugget Index::525]]}}
}}

== Introduction ==

As all students of solar activity know, the
[https://www.stce.be/educational/classification naming scheme]
for solar flares involves the letters ABCMX.
These date from the dawn of the space age, when the first
[https://en.wikipedia.org/wiki/SOLRAD SOLRAD] satellites began to monitor
solar X-ray emission.
Flares of a wide range of brightnesses were immediately apparent, and
[https://www.noaa.gov NOAA]
ionospheric physicist Don Baker (Ref. [1]) came up with a classification
that matched decades of peak flux to letters: Cnn would mean nn x 10-4,
and the basic flux level 1.0 x 10-6 W/m2 would be class C1.0.
Initially it was just CMX ("Common", "Medium", "Extreme")
Each flare has a peak flux in the standard 1-8 Å band,
and the range of magnitudes of flare peak fluxes is so great that it's most
convenient to record the
[https://en.wikipedia.org/wiki/Common_logarithm logarithm] of the
flux.
This convention moved directly into the
[https://www.swpc.noaa.gov/products/goes-x-ray-flux GOES]
satellite era, and from 1974 the standardized flux measurements
have come from this series of spacecraft (Ref. [2]).

In standard units a C-class flare has a peak flux greater than 10-6
W/m2, with M-class and X-class greater by powers of 10.
Conventionally a flare 10% brighter than the threshold, with peak flux
1.1 x 10-6 W/m2, would then become a C1.1 flare.
The letter thus represents the truncated logarithm of the peak flux.
The magnitudes are not rounded off and represent the solar X-ray flux
conventionally in a 1-min integration interval.
A background quiescent solar emission level is not subtracted; these routine
observations show the total solar X-ray flux in "Sun-as-a-star" mode.
Weaker events near the background level, which can indeed exceed C1 during
active times, will thus not be quite as energetic as their name implies.

Low background solar X-ray fluxes during solar minima allowed the GOES
detector technology to detect fainter events, and so two new decades were
added to the letter string: A and B, with no particular descriptive
interpretation.
Thus we arrived at the current letter string ABCMX.

== The SphinX breakthrough (to the bottom) ==

The first routine flare monitoring with sufficient sensitivity to
detect the solar quiescent X-ray flux appeared with the SphinX
instrument from the
[https://scholar.google.com/citations?user=vDLMZPIAAAAJ&hl=pl Sylwester]
group at Wroc&lstrok;aw (Ref. [3]).
For 1-8 Å this turned out to be about two decades below the A level.
Hence, two more letters: Q "quiet" and S "small", leading to the more complete
string QSABCMX.
Figure 1 shows SphinX data from the 2009
[https://en.wikipedia.org/wiki/Solar_cycle solar minimum].

[[File:526f1.png|center|thumb|600px|caption|Figure 1: 
SphinX observations from solar minimum 2009, showing microflares down to the Q level
(as indicated by vertical blue lines at the bottom).
The regions marked with red show times of SphinX minimum counting rate, at levels far
below the original CMX range (Ref. [3]).
Green regions contain microflare excesses.
Excesses above this level are due to weak flares and quiescent active regions.
Translated to the GOES calibration, the weakest events are measured in units of
10-10 W/m2.
]]

== The greatest events (to the top) ==

At the top end of the GOES soft X-ray distribution, a handful of the most
extreme events had saturated the GOES 1-8 Å readout.
Ref. [4] describes an evenhanded patching of these items, together with a
correction for a systematic offset (Ref. [2]).
This produced a list of 37 >X10 events after background subtraction.
This basic manipulation departs from tradition, and so we provide this
[https://www.astro.gla.ac.uk/users/hsh3f/QSabcmxyz.txt greatest flares catalog]
(a ~2 MB .psf file) using the letter system "QSabcmxyz".
To translate, the new "y" class is the old "X10" class, sometimes now called
"S" (Ref. 5]), and the new catalog lists 37 of them.
The new "z" class has no examples yet (but we're hopeful), although the
[https://heliowiki.smce.nasa.gov/wiki/index.php/The_1859_Space_Weather_Event_Revisited Carrington event]
might have been in that category.

A sample of the newly lettered catalog is here, representing a signal-to-background requirement of 1 (flare
doubles the preflare level), resulting in a reduction of total number from 48,131 to 42,469 for the timespan
1974-2023.
The new letter string is QSabcmxyz, pleasingly symmetric.

Index ABCMX class QSabcmxyz
..
13190 SOL1989-03-05T23:56 C5.2 c4.65
13191 SOL1989-03-06T00:20 C5.1 c4.18
13192 SOL1989-03-06T00:39 C7.1 c7.55
13193 SOL1989-03-06T01:18 M3.0 m3.73
13194 SOL1989-03-06T03:23 M2.5 m3.37
13195 SOL1989-03-06T04:33 C4.6 c4.51
13196 SOL1989-03-06T11:42 C8.2 c9.89
13197 SOL1989-03-06T12:32 C4.9 c5.41
13198 SOL1989-03-06T14:10 X15. y1.90
13199 SOL1989-03-07T05:58 M2.0 m2.48
13200 SOL1989-03-07T11:14 C6.5 c5.79
13201 SOL1989-03-07T13:27 M4.1 m5.56
13202 SOL1989-03-07T13:44 M2.4 m5.57
13203 SOL1989-03-07T14:54 X1.8 x2.69
..
The catalog contains 37 y-class events (previously X10 or S), but no z-class examples because the Sun refuses to
cooperate. At the C (--> c) level, many events get downgraded because of background subtraction, but the systematic
historical scale adjustment described in Ref. [2] tends to compensate for that.

== Conclusions ==

See the [https://www.astro.gla.ac.uk/users/hsh3f/QSabcmxyz.html further discussion] of how QSabcmxyz works, or to access it directly click [https://www.astro.gla.ac.uk/users/hsh3f/QSabcmxyz.txt here] for a 2-MB text listing.

== Acknowledgment ==

We thank Janusz Sylwester for help in understanding the pioneering SphinX data.

== References ==

[1] "Sentinels of the sun: forecasting space weather," B. Poppe and K. Jorden, 2006

[2] [https://www.sciencedirect.com/science/article/pii/B9780128143278000196 "GOES-R Series Solar X-ray and Ultraviolet Irradiance"]

[3] [https://doi.org/10.1007/s11207-019-1565-9 "Analysis of Quiescent Corona X-ray Spectra from SphinX During the 2009 Solar Minimum"]

[4] [https://ui.adsabs.harvard.edu/abs/2024SoPh..299...39H "The Greatest GOES Soft X-ray Flares"]

[5] [https://ui.adsabs.harvard.edu/abs/2025ApJ...979L..16T "The Occurrence of Powerful Flares Stronger than X10 Class in Solar Cycles"]

X-ray Log Letters

2026-05-26T11:05:35Z

Hhudson: /* Introduction */

{{Infobox Nugget |name = Nugget
|title = X-ray Log Letters
|number = 526
|first_author = Hugh HUDSON and
|second_author = Ed CLIVER
|publish_date = May 18, 2026
|next_nugget = TBD
|previous_nugget = {{#ask: [[Category:Nugget]] [[RHESSI Nugget Index::525]]}}
}}

== Introduction ==

As all students of solar activity know, the
[https://www.stce.be/educational/classification naming scheme]
for solar flares involves the letters ABCMX.
These date from the dawn of the space age, when the first
[https://en.wikipedia.org/wiki/SOLRAD SOLRAD] satellites began to monitor
solar X-ray emission.
Flares of a wide range of brightnesses were immediately apparent, and
[https://www.noaa.gov NOAA]
ionospheric physicist Don Baker (Ref. [1]) came up with a classification
that matched decades of peak flux to letters: Cnn would mean nn x 10-4,
and the basic flux level 1.0 x 10-6 W/m2 would be class C1.0.
Initially it was just CMX ("Common", "Medium", "Extreme")
Each flare has a peak flux in the standard 1-8 Å band,
and the range of magnitudes of flare peak fluxes is so great that it's most
convenient to record the
[https://en.wikipedia.org/wiki/Common_logarithm logarithm] of the
flux.
This convention moved directly into the
[https://www.swpc.noaa.gov/products/goes-x-ray-flux GOES]
satellite era, and from 1974 the standardized flux measurements
have come from this series of spacecraft (Ref. [2]).

In standard units a C-class flare has a peak flux greater than 10-6
W/m2, with M-class and X-class greater by powers of 10.
Conventionally a flare 10% brighter than the threshold, with peak flux
1.1 x 10-6 W/m2, would then become a C1.1 flare.
The letter thus represents the truncated logarithm of the peak flux.
The magnitudes are not rounded off and represent the solar X-ray flux
conventionally in a 1-min integration interval.
A background quiescent solar emission level is not subtracted; these routine
observations show the total solar X-ray flux in "Sun-as-a-star" mode.
Weaker events near the background level, which can indeed exceed C1 during
active times, will thus not be quite as energetic as their name implies.

Low background solar X-ray fluxes during solar minima allowed the GOES
detector technology to detect fainter events, and so two new decades were
added to the letter string: A and B, with no particular descriptive
interpretation.
Thus we arrived at the current letter string ABCMX.

== The SphinX breakthrough (to the bottom) ==

The first routine flare monitoring with sufficient sensitivity to
detect the solar quiescent X-ray flux appeared with the SphinX
instrument from the
[https://scholar.google.com/citations?user=vDLMZPIAAAAJ&hl=pl Sylwester]
group at Wroc&lstrok;aw (Ref. [3]).
For 1-8 Å this turned out to be about two decades below the A level.
Hence, two more letters: Q "quiet" and S "small", leading to the more complete
string QSABCMX.
Figure 1 shows SphinX data from the 2009
[https://en.wikipedia.org/wiki/Solar_cycle solar minimum].

[[File:526f1.png|center|thumb|600px|caption|Figure 1: 
SphinX observations from solar minimum 2009, showing microflares down to the Q level
(as indicated by vertical blue lines at the bottom).
The regions marked with red show times of SphinX minimum counting rate, at levels far
below the original CMX range (Ref. [3]).
Green regions contain microflare excesses.
Excesses above this level are due to weak flares and quiescent active regions.
Translated to the GOES calibration, the weakest events are measured in units of
10-10 W/m2.
]]

== The greatest events (to the top) ==

At the top end of the GOES soft X-ray distribution, a handful of the most
extreme events had saturated the GOES 1-8 Å readout.
Ref. [4] describes an evenhanded patching of these items, together with a
correction for a systematic offset (Ref. [2]).
This produced a list of 37 >X10 events after background subtraction.
This basic manipulation departs from tradition, and so we provide this
[https://www.astro.gla.ac.uk/users/hsh3f/QSabcmxyz.txt greatest flares catalog]
(a ~2 MB .psf file) using the letter system "QSabcmxyz".
To translate, the new "y" class is the old "X10" class, sometimes now called
"S" (Ref. 5]), and the new catalog lists 37 of them.
The new "z" class has no examples yet (but we're hopeful), although the
[https://heliowiki.smce.nasa.gov/wiki/index.php/The_1859_Space_Weather_Event_Revisited Carrington event]
might have been in that category.

A sample of the newly lettered catalog is here, representing a signal-to-background requirement of 1 (flare
doubles the preflare level), resulting in a reduction of total number from 48,131 to 42,469 for the timespan
1974-2023.
The new letter string is QSabcmxyz, pleasingly symmetric.

Index ABCMX class QSabcmxyz
..
13190 SOL1989-03-05T23:56 C5.2 c4.65
13191 SOL1989-03-06T00:20 C5.1 c4.18
13192 SOL1989-03-06T00:39 C7.1 c7.55
13193 SOL1989-03-06T01:18 M3.0 m3.73
13194 SOL1989-03-06T03:23 M2.5 m3.37
13195 SOL1989-03-06T04:33 C4.6 c4.51
13196 SOL1989-03-06T11:42 C8.2 c9.89
13197 SOL1989-03-06T12:32 C4.9 c5.41
13198 SOL1989-03-06T14:10 X15. y1.90
13199 SOL1989-03-07T05:58 M2.0 m2.48
13200 SOL1989-03-07T11:14 C6.5 c5.79
13201 SOL1989-03-07T13:27 M4.1 m5.56
13202 SOL1989-03-07T13:44 M2.4 m5.57
13203 SOL1989-03-07T14:54 X1.8 x2.69
..
The catalog contains 37 y-class events (previously X10 or S), but no z-class examples because the Sun refuses to
cooperate. At the C (--> c) level, many events get downgraded because of background subtraction, but the systematic
historical scale adjustment described in Ref. [2] tends to compensate for that.

== Conclusions ==

See the [https://www.astro.gla.ac.uk/users/hsh3f/QSabcmxyz.html further discussion] of how QSabcmxyz works, or to access it directly click [https://www.astro.gla.ac.uk/users/hsh3f/QSabcmxyz.txt here] for a 2-MB text listing.

== References ==

[1] "Sentinels of the sun: forecasting space weather," B. Poppe and K. Jorden, 2006

[2] [https://www.sciencedirect.com/science/article/pii/B9780128143278000196 "GOES-R Series Solar X-ray and Ultraviolet Irradiance"]

[3] [https://doi.org/10.1007/s11207-019-1565-9 "Analysis of Quiescent Corona X-ray Spectra from SphinX During the 2009 Solar Minimum"]

[4] [https://ui.adsabs.harvard.edu/abs/2024SoPh..299...39H "The Greatest GOES Soft X-ray Flares"]

[5] [https://ui.adsabs.harvard.edu/abs/2025ApJ...979L..16T "The Occurrence of Powerful Flares Stronger than X10 Class in Solar Cycles"]

X-ray Log Letters

2026-05-26T11:04:41Z

Hhudson: /* Introduction */ Warmuth correction

{{Infobox Nugget |name = Nugget
|title = X-ray Log Letters
|number = 526
|first_author = Hugh HUDSON and
|second_author = Ed CLIVER
|publish_date = May 18, 2026
|next_nugget = TBD
|previous_nugget = {{#ask: [[Category:Nugget]] [[RHESSI Nugget Index::525]]}}
}}

== Introduction ==

As all students of solar activity know, the
[https://www.stce.be/educational/classification naming scheme]
for solar flares involves the letters ABCMX.
These date from the dawn of the space age, when the first
[https://en.wikipedia.org/wiki/SOLRAD SOLRAD] satellites began to monitor
solar X-ray emission.
Flares of a wide range of brightnesses were immediately apparent, and
[https://www.noaa.gov NOAA]
ionospheric physicist Don Baker (Ref. [1]) came up with a classification
that matched decades of peak flux to letters: Cnn would mean nn x 10-4,
and the basic flux level 1.0 x 10-6 W/m2 would be class C1.0.
Initially it was just CMX ("Common", "Medium", "Extreme")
Each flare has a peak flux in the standard 1-8 Å band,
and the range of magnitudes of flare peak fluxes is so great that it's most
convenient to record the
[https://en.wikipedia.org/wiki/Common_logarithm logarithm] of the
flux.
This convention moved directly into the
[https://www.swpc.noaa.gov/products/goes-x-ray-flux GOES]
satellite era, and from 1974 the standardized flux measurements
have come from this series of spacecraft (Ref. [2]).

In standard units a C-class flare has a peak flux greater than 10-7
W/m2, with M-class and X-class greater by powers of 10.
Conventionally a flare 10% brighter than the threshold, with peak flux
1.1 x 10-6 W/m2, would then become a C1.1 flare.
The letter thus represents the truncated logarithm of the peak flux.
The magnitudes are not rounded off and represent the solar X-ray flux
conventionally in a 1-min integration interval.
A background quiescent solar emission level is not subtracted; these routine
observations show the total solar X-ray flux in "Sun-as-a-star" mode.
Weaker events near the background level, which can indeed exceed C1 during
active times, will thus not be quite as energetic as their name implies.

Low background solar X-ray fluxes during solar minima allowed the GOES
detector technology to detect fainter events, and so two new decades were
added to the letter string: A and B, with no particular descriptive
interpretation.
Thus we arrived at the current letter string ABCMX.

== The SphinX breakthrough (to the bottom) ==

The first routine flare monitoring with sufficient sensitivity to
detect the solar quiescent X-ray flux appeared with the SphinX
instrument from the
[https://scholar.google.com/citations?user=vDLMZPIAAAAJ&hl=pl Sylwester]
group at Wroc&lstrok;aw (Ref. [3]).
For 1-8 Å this turned out to be about two decades below the A level.
Hence, two more letters: Q "quiet" and S "small", leading to the more complete
string QSABCMX.
Figure 1 shows SphinX data from the 2009
[https://en.wikipedia.org/wiki/Solar_cycle solar minimum].

[[File:526f1.png|center|thumb|600px|caption|Figure 1: 
SphinX observations from solar minimum 2009, showing microflares down to the Q level
(as indicated by vertical blue lines at the bottom).
The regions marked with red show times of SphinX minimum counting rate, at levels far
below the original CMX range (Ref. [3]).
Green regions contain microflare excesses.
Excesses above this level are due to weak flares and quiescent active regions.
Translated to the GOES calibration, the weakest events are measured in units of
10-10 W/m2.
]]

== The greatest events (to the top) ==

At the top end of the GOES soft X-ray distribution, a handful of the most
extreme events had saturated the GOES 1-8 Å readout.
Ref. [4] describes an evenhanded patching of these items, together with a
correction for a systematic offset (Ref. [2]).
This produced a list of 37 >X10 events after background subtraction.
This basic manipulation departs from tradition, and so we provide this
[https://www.astro.gla.ac.uk/users/hsh3f/QSabcmxyz.txt greatest flares catalog]
(a ~2 MB .psf file) using the letter system "QSabcmxyz".
To translate, the new "y" class is the old "X10" class, sometimes now called
"S" (Ref. 5]), and the new catalog lists 37 of them.
The new "z" class has no examples yet (but we're hopeful), although the
[https://heliowiki.smce.nasa.gov/wiki/index.php/The_1859_Space_Weather_Event_Revisited Carrington event]
might have been in that category.

A sample of the newly lettered catalog is here, representing a signal-to-background requirement of 1 (flare
doubles the preflare level), resulting in a reduction of total number from 48,131 to 42,469 for the timespan
1974-2023.
The new letter string is QSabcmxyz, pleasingly symmetric.

Index ABCMX class QSabcmxyz
..
13190 SOL1989-03-05T23:56 C5.2 c4.65
13191 SOL1989-03-06T00:20 C5.1 c4.18
13192 SOL1989-03-06T00:39 C7.1 c7.55
13193 SOL1989-03-06T01:18 M3.0 m3.73
13194 SOL1989-03-06T03:23 M2.5 m3.37
13195 SOL1989-03-06T04:33 C4.6 c4.51
13196 SOL1989-03-06T11:42 C8.2 c9.89
13197 SOL1989-03-06T12:32 C4.9 c5.41
13198 SOL1989-03-06T14:10 X15. y1.90
13199 SOL1989-03-07T05:58 M2.0 m2.48
13200 SOL1989-03-07T11:14 C6.5 c5.79
13201 SOL1989-03-07T13:27 M4.1 m5.56
13202 SOL1989-03-07T13:44 M2.4 m5.57
13203 SOL1989-03-07T14:54 X1.8 x2.69
..
The catalog contains 37 y-class events (previously X10 or S), but no z-class examples because the Sun refuses to
cooperate. At the C (--> c) level, many events get downgraded because of background subtraction, but the systematic
historical scale adjustment described in Ref. [2] tends to compensate for that.

== Conclusions ==

See the [https://www.astro.gla.ac.uk/users/hsh3f/QSabcmxyz.html further discussion] of how QSabcmxyz works, or to access it directly click [https://www.astro.gla.ac.uk/users/hsh3f/QSabcmxyz.txt here] for a 2-MB text listing.

== References ==

[1] "Sentinels of the sun: forecasting space weather," B. Poppe and K. Jorden, 2006

[2] [https://www.sciencedirect.com/science/article/pii/B9780128143278000196 "GOES-R Series Solar X-ray and Ultraviolet Irradiance"]

[3] [https://doi.org/10.1007/s11207-019-1565-9 "Analysis of Quiescent Corona X-ray Spectra from SphinX During the 2009 Solar Minimum"]

[4] [https://ui.adsabs.harvard.edu/abs/2024SoPh..299...39H "The Greatest GOES Soft X-ray Flares"]

[5] [https://ui.adsabs.harvard.edu/abs/2025ApJ...979L..16T "The Occurrence of Powerful Flares Stronger than X10 Class in Solar Cycles"]

Space Weather Impact of Three Solar Flares Observed at Millimeter Wavelengths

2026-05-26T06:59:02Z

Hhudson: /* References */

{{Infobox Nugget |name = Nugget
|title = Space Weather Impact of Three Solar Flares Observed at Millimeter Wavelengths
|number = 527
|first_author = Adriana VALIO et al.
|publish_date = May 25, 2026
|next_nugget = TBD
|previous_nugget = {{#ask: [[Category:Nugget]] [[RHESSI Nugget Index::526]]}}
}}

== Introduction ==

Solar flares are among the most energetic events in the solar system,
releasing vast amounts of energy across the electromagnetic spectrum
(from radio waves to gamma-rays) in a matter of minutes to hours.
Long-duration events are especially important because their prolonged
magnetic reconnection continuously accelerates particles, pumping
energy into the heliosphere long after the initial impulsive phase
has ended. Understanding the link between the properties of these
flares, the coronal mass ejections (CMEs) launched simultaneously,
and the disturbances caused at Earth is a central challenge of space
weather science.

One key area of observation of these phenomena -- millimeter radio waves -- has not been so well exploited.
The
[https://en.wikipedia.org/wiki/POlarization_Emission_of_Millimeter_Activity_at_the_Sun POEMAS]
telescope fills this key gap by making systematic solar observations at
45 and 90 Ghz (6.6 and 3.3 mm), crucial to understanding the
[https://en.wikipedia.org/wiki/Synchrotron_radiation gyrosynchrotron radiation]
fundamental to flare development.

We used this facility to carry out a detailed multiwavelength analysis (Ref. [1]) of
three long-duration solar flares during the solar maximum period of 2012
(Ref. [1]):
SOL2012-03-02 (M3.3; m4.80)
SOL2012-06-06 (M2.1; m3.07)
SOL2012-07-12 (X1.4; x1.85)
The adjusted ABCMX classes come from
[https://heliowiki.smce.nasa.gov/wiki/index.php/X-ray_Log_Letters] the previous Nugget]
as an experiment here; by either class scheme these events span a factor of 40
in magnitude.
The POEMAS high-frequency observations include measurements of circular
polarization, a key attribute not otherwise available.

== Radio Bursts and Gyrosynchrotron Modelling ==

Each flare was observed in both millimeter emission (POEMAS at 45
and 90 GHz) and microwaves
(the [https://en.wikipedia.org/wiki/STN Radio_Solar_Telescope_Network] at 1–15 GHz).
Combined radio spectra
spanning 5–90 GHz were assembled at four time intervals during each
burst and fitted with a gyrosynchrotron model using a Markov Chain
Monte Carlo (MCMC) algorithm. The fits yield four key physical
parameters: the magnetic field strength Bmag, the total number of
accelerated electrons Ne, the source size a, and the
spectral index of the electron energy distribution δ.

A main result is that all three events return remarkably similar
magnetic field strengths of about 160–180 G, despite the enormous
differences in overall flare energy.
This suggests a common coronal
magnetic configuration for these gyrosynchrotron-emitting sources,
and that what distinguishes powerful from weaker events is primarily
the number of electrons accelerated and the spatial extent of the
emitting region, not the field strength itself.
SOL2012-07-12 (X1.4; Figure 1)
had a source diameter roughly 3–6 times larger than the
other events and accelerated 6–13 times more electrons.
The spectral index δ was about 2.8 across all events,
harder than the typical microwave
range of 3–5.
This reflects a bias toward energetic events at millimeter
wavelengths, where only hard-spectrum flares produce detectable
flux at 90 GHz. In all three cases δ hardened further as each burst
progressed, reaching values near 2 by the end of the event.
The June and July flares also showed flux at 90 GHz exceeding that at
45 GHz, a "sub-THz component" previously reported by Ref. [2]
and indicating an additional emission mechanism at the
highest frequencies, distinct from the standard gyrosynchrotron
component.

[[File:527f1.png|center|thumb|700px|caption|Figure 1: 
Top row: Extreme ultraviolet (EUV) images captured by the Atmospheric
Imaging Assembly (AIA) instrument onboard the Solar Dynamics
Observatory (SDO) satellite, showing the SOL2012‐07‐12 flare at 171 Å
(left panel) and 304 Å (right panel). Bottom row: Light curves
of the SOL2012‐07‐12 flare. Left panel: Soft X‐ray emission observed
by GOES, with high‐energy (blue curve) and low‐energy (red curve)
channels. Right panel: Radio flux density light curves from 2 to
15 GHz recorded by RSTN, and at 45 and 90 GHz (red curve) observed
by POEMAS. The vertical red dashed line represents the approximate
launch time of the associated CME.
]]

== CMEs and Space Weather ==

Each of the three flares was accompanied by a coronal mass ejection
(CME) detected by LASCO/SOHO, and in all three cases the CME was
launched essentially simultaneously with the radio burst onset.
Two of the three events led to geomagnetic storms, as measured
by the
[https://wdc.kugi.kyoto-u.ac.jp/dstdir/ Dst index].
Notably the interaction of the July ICME with the magnetosphere also
triggered [https://en.wikipedia.org/wiki/Aurora aurora australis],
photographed by the crew of the International Space Station on 15 July 2012.

[[File:527f2.png|center|thumb|800px|caption|Figure 1: 
Scatter plots showing the positive correlation between the absolute
minimum Dst geomagnetic index (left) and CME velocity measured from
coronagraph observations (right) with the peak radio flux at 45 GH
Note that the March CME event missed Earth.
]]

== Conclusions ==

The central finding of this study is a consistent positive correlation
between the peak radio flux measured at 45 GHz and a suite of space
weather indicators: GOES flare class, SXR energy, CME velocity and
kinetic energy, ionospheric D-region depression, and geomagnetic
storm severity as quantified by Dst and Kp (Figure 2). The X1.4
event on 12 July 2012 sat at the high end of all these scales
simultaneously producing the brightest millimeter burst (116 SFU
at 45 GHz), the fastest and most energetic CME (884 km/s, 2.7 ×
1031 ergs), the deepest ionospheric depression (9 km), and the
strongest geomagnetic storm (Dst = −139 nT) of the three events.

The magnetic field strength in the gyrosynchrotron-emitting source
(~160–180 G) was essentially the same in all three flares, pointing
to a common magnetic topology. What differentiated the events was
the number of accelerated electrons and the source volume. Moreover,
the spectral index δ, consistently hard (~2.8, hardening toward 2
as each burst progressed), is characteristic of the millimeter-emitting
population and harder than what is typically inferred from
microwave-only studies, reflecting a selection effect at the highest
frequencies.

High-frequency millimeter radio observations thus appear to be a
promising tool for early space weather assessment: they are sensitive
to the most energetic particle populations, they respond on the
same timescale as the flare itself (allowing prediction hours or
even days before a CME arrives), and they correlate well with both
the CME properties and the ultimate geomagnetic impact. POEMAS
recorded 49 solar radio bursts during the 2012–2013 solar maximum,
at least half associated with halo or partial halo CMEs, offering
a valuable archive for extending this type of analysis to a larger
statistical sample.

== Acknowledgment ==

The authors of Ref. [1] and this Nugget are A. Valio, K.F. Lopez, J.L.
Gamonal Valenzuela, R.M. Romero Ramírez, and D.F. da Silva.

== References ==

[1] [https://ui.adsabs.harvard.edu/abs/2025JGRA..13034611V "Space weather impacts of three solar flares observed by the POEMAS telescope at 45 and 90 GHz"]

[2] [http://adsabs.harvard.edu/abs/2004ApJ...603L.121K "A new solar burst spectral component emitting only in the terahertz range:]

[3] [https://ui.adsabs.harvard.edu/abs/2013SoPh..283..651V "New circular polarization solar telescopes at two millimeter wavelength ranges"]

Space Weather Impact of Three Solar Flares Observed at Millimeter Wavelengths

2026-05-26T06:58:31Z

Hhudson: /* References */

{{Infobox Nugget |name = Nugget
|title = Space Weather Impact of Three Solar Flares Observed at Millimeter Wavelengths
|number = 527
|first_author = Adriana VALIO et al.
|publish_date = May 25, 2026
|next_nugget = TBD
|previous_nugget = {{#ask: [[Category:Nugget]] [[RHESSI Nugget Index::526]]}}
}}

== Introduction ==

Solar flares are among the most energetic events in the solar system,
releasing vast amounts of energy across the electromagnetic spectrum
(from radio waves to gamma-rays) in a matter of minutes to hours.
Long-duration events are especially important because their prolonged
magnetic reconnection continuously accelerates particles, pumping
energy into the heliosphere long after the initial impulsive phase
has ended. Understanding the link between the properties of these
flares, the coronal mass ejections (CMEs) launched simultaneously,
and the disturbances caused at Earth is a central challenge of space
weather science.

One key area of observation of these phenomena -- millimeter radio waves -- has not been so well exploited.
The
[https://en.wikipedia.org/wiki/POlarization_Emission_of_Millimeter_Activity_at_the_Sun POEMAS]
telescope fills this key gap by making systematic solar observations at
45 and 90 Ghz (6.6 and 3.3 mm), crucial to understanding the
[https://en.wikipedia.org/wiki/Synchrotron_radiation gyrosynchrotron radiation]
fundamental to flare development.

We used this facility to carry out a detailed multiwavelength analysis (Ref. [1]) of
three long-duration solar flares during the solar maximum period of 2012
(Ref. [1]):
SOL2012-03-02 (M3.3; m4.80)
SOL2012-06-06 (M2.1; m3.07)
SOL2012-07-12 (X1.4; x1.85)
The adjusted ABCMX classes come from
[https://heliowiki.smce.nasa.gov/wiki/index.php/X-ray_Log_Letters] the previous Nugget]
as an experiment here; by either class scheme these events span a factor of 40
in magnitude.
The POEMAS high-frequency observations include measurements of circular
polarization, a key attribute not otherwise available.

== Radio Bursts and Gyrosynchrotron Modelling ==

Each flare was observed in both millimeter emission (POEMAS at 45
and 90 GHz) and microwaves
(the [https://en.wikipedia.org/wiki/STN Radio_Solar_Telescope_Network] at 1–15 GHz).
Combined radio spectra
spanning 5–90 GHz were assembled at four time intervals during each
burst and fitted with a gyrosynchrotron model using a Markov Chain
Monte Carlo (MCMC) algorithm. The fits yield four key physical
parameters: the magnetic field strength Bmag, the total number of
accelerated electrons Ne, the source size a, and the
spectral index of the electron energy distribution δ.

A main result is that all three events return remarkably similar
magnetic field strengths of about 160–180 G, despite the enormous
differences in overall flare energy.
This suggests a common coronal
magnetic configuration for these gyrosynchrotron-emitting sources,
and that what distinguishes powerful from weaker events is primarily
the number of electrons accelerated and the spatial extent of the
emitting region, not the field strength itself.
SOL2012-07-12 (X1.4; Figure 1)
had a source diameter roughly 3–6 times larger than the
other events and accelerated 6–13 times more electrons.
The spectral index δ was about 2.8 across all events,
harder than the typical microwave
range of 3–5.
This reflects a bias toward energetic events at millimeter
wavelengths, where only hard-spectrum flares produce detectable
flux at 90 GHz. In all three cases δ hardened further as each burst
progressed, reaching values near 2 by the end of the event.
The June and July flares also showed flux at 90 GHz exceeding that at
45 GHz, a "sub-THz component" previously reported by Ref. [2]
and indicating an additional emission mechanism at the
highest frequencies, distinct from the standard gyrosynchrotron
component.

[[File:527f1.png|center|thumb|700px|caption|Figure 1: 
Top row: Extreme ultraviolet (EUV) images captured by the Atmospheric
Imaging Assembly (AIA) instrument onboard the Solar Dynamics
Observatory (SDO) satellite, showing the SOL2012‐07‐12 flare at 171 Å
(left panel) and 304 Å (right panel). Bottom row: Light curves
of the SOL2012‐07‐12 flare. Left panel: Soft X‐ray emission observed
by GOES, with high‐energy (blue curve) and low‐energy (red curve)
channels. Right panel: Radio flux density light curves from 2 to
15 GHz recorded by RSTN, and at 45 and 90 GHz (red curve) observed
by POEMAS. The vertical red dashed line represents the approximate
launch time of the associated CME.
]]

== CMEs and Space Weather ==

Each of the three flares was accompanied by a coronal mass ejection
(CME) detected by LASCO/SOHO, and in all three cases the CME was
launched essentially simultaneously with the radio burst onset.
Two of the three events led to geomagnetic storms, as measured
by the
[https://wdc.kugi.kyoto-u.ac.jp/dstdir/ Dst index].
Notably the interaction of the July ICME with the magnetosphere also
triggered [https://en.wikipedia.org/wiki/Aurora aurora australis],
photographed by the crew of the International Space Station on 15 July 2012.

[[File:527f2.png|center|thumb|800px|caption|Figure 1: 
Scatter plots showing the positive correlation between the absolute
minimum Dst geomagnetic index (left) and CME velocity measured from
coronagraph observations (right) with the peak radio flux at 45 GH
Note that the March CME event missed Earth.
]]

== Conclusions ==

The central finding of this study is a consistent positive correlation
between the peak radio flux measured at 45 GHz and a suite of space
weather indicators: GOES flare class, SXR energy, CME velocity and
kinetic energy, ionospheric D-region depression, and geomagnetic
storm severity as quantified by Dst and Kp (Figure 2). The X1.4
event on 12 July 2012 sat at the high end of all these scales
simultaneously producing the brightest millimeter burst (116 SFU
at 45 GHz), the fastest and most energetic CME (884 km/s, 2.7 ×
1031 ergs), the deepest ionospheric depression (9 km), and the
strongest geomagnetic storm (Dst = −139 nT) of the three events.

The magnetic field strength in the gyrosynchrotron-emitting source
(~160–180 G) was essentially the same in all three flares, pointing
to a common magnetic topology. What differentiated the events was
the number of accelerated electrons and the source volume. Moreover,
the spectral index δ, consistently hard (~2.8, hardening toward 2
as each burst progressed), is characteristic of the millimeter-emitting
population and harder than what is typically inferred from
microwave-only studies, reflecting a selection effect at the highest
frequencies.

High-frequency millimeter radio observations thus appear to be a
promising tool for early space weather assessment: they are sensitive
to the most energetic particle populations, they respond on the
same timescale as the flare itself (allowing prediction hours or
even days before a CME arrives), and they correlate well with both
the CME properties and the ultimate geomagnetic impact. POEMAS
recorded 49 solar radio bursts during the 2012–2013 solar maximum,
at least half associated with halo or partial halo CMEs, offering
a valuable archive for extending this type of analysis to a larger
statistical sample.

== Acknowledgment ==

The authors of Ref. [1] and this Nugget are A. Valio, K.F. Lopez, J.L.
Gamonal Valenzuela, R.M. Romero Ramírez, and D.F. da Silva.

== References ==

[1] [https://ui.adsabs.harvard.edu/abs/2025JGRA..13034611V "Space weather impacts of three solar flares observed by the POEMAS telescope at 45 and 90 GHz"]

[2] [http://adsabs.harvard.edu/abs/2004ApJ...603L.121K "A new solar burst spectral component emitting only in the terahertz range:]

[3] [ https://ui.adsabs.harvard.edu/abs/2013SoPh..283..651V "New circular polarization solar telescopes at two millimeter wavelength ranges"]

Space Weather Impact of Three Solar Flares Observed at Millimeter Wavelengths

2026-05-26T06:57:45Z

Hhudson: /* References */

{{Infobox Nugget |name = Nugget
|title = Space Weather Impact of Three Solar Flares Observed at Millimeter Wavelengths
|number = 527
|first_author = Adriana VALIO et al.
|publish_date = May 25, 2026
|next_nugget = TBD
|previous_nugget = {{#ask: [[Category:Nugget]] [[RHESSI Nugget Index::526]]}}
}}

== Introduction ==

Solar flares are among the most energetic events in the solar system,
releasing vast amounts of energy across the electromagnetic spectrum
(from radio waves to gamma-rays) in a matter of minutes to hours.
Long-duration events are especially important because their prolonged
magnetic reconnection continuously accelerates particles, pumping
energy into the heliosphere long after the initial impulsive phase
has ended. Understanding the link between the properties of these
flares, the coronal mass ejections (CMEs) launched simultaneously,
and the disturbances caused at Earth is a central challenge of space
weather science.

One key area of observation of these phenomena -- millimeter radio waves -- has not been so well exploited.
The
[https://en.wikipedia.org/wiki/POlarization_Emission_of_Millimeter_Activity_at_the_Sun POEMAS]
telescope fills this key gap by making systematic solar observations at
45 and 90 Ghz (6.6 and 3.3 mm), crucial to understanding the
[https://en.wikipedia.org/wiki/Synchrotron_radiation gyrosynchrotron radiation]
fundamental to flare development.

We used this facility to carry out a detailed multiwavelength analysis (Ref. [1]) of
three long-duration solar flares during the solar maximum period of 2012
(Ref. [1]):
SOL2012-03-02 (M3.3; m4.80)
SOL2012-06-06 (M2.1; m3.07)
SOL2012-07-12 (X1.4; x1.85)
The adjusted ABCMX classes come from
[https://heliowiki.smce.nasa.gov/wiki/index.php/X-ray_Log_Letters] the previous Nugget]
as an experiment here; by either class scheme these events span a factor of 40
in magnitude.
The POEMAS high-frequency observations include measurements of circular
polarization, a key attribute not otherwise available.

== Radio Bursts and Gyrosynchrotron Modelling ==

Each flare was observed in both millimeter emission (POEMAS at 45
and 90 GHz) and microwaves
(the [https://en.wikipedia.org/wiki/STN Radio_Solar_Telescope_Network] at 1–15 GHz).
Combined radio spectra
spanning 5–90 GHz were assembled at four time intervals during each
burst and fitted with a gyrosynchrotron model using a Markov Chain
Monte Carlo (MCMC) algorithm. The fits yield four key physical
parameters: the magnetic field strength Bmag, the total number of
accelerated electrons Ne, the source size a, and the
spectral index of the electron energy distribution δ.

A main result is that all three events return remarkably similar
magnetic field strengths of about 160–180 G, despite the enormous
differences in overall flare energy.
This suggests a common coronal
magnetic configuration for these gyrosynchrotron-emitting sources,
and that what distinguishes powerful from weaker events is primarily
the number of electrons accelerated and the spatial extent of the
emitting region, not the field strength itself.
SOL2012-07-12 (X1.4; Figure 1)
had a source diameter roughly 3–6 times larger than the
other events and accelerated 6–13 times more electrons.
The spectral index δ was about 2.8 across all events,
harder than the typical microwave
range of 3–5.
This reflects a bias toward energetic events at millimeter
wavelengths, where only hard-spectrum flares produce detectable
flux at 90 GHz. In all three cases δ hardened further as each burst
progressed, reaching values near 2 by the end of the event.
The June and July flares also showed flux at 90 GHz exceeding that at
45 GHz, a "sub-THz component" previously reported by Ref. [2]
and indicating an additional emission mechanism at the
highest frequencies, distinct from the standard gyrosynchrotron
component.

[[File:527f1.png|center|thumb|700px|caption|Figure 1: 
Top row: Extreme ultraviolet (EUV) images captured by the Atmospheric
Imaging Assembly (AIA) instrument onboard the Solar Dynamics
Observatory (SDO) satellite, showing the SOL2012‐07‐12 flare at 171 Å
(left panel) and 304 Å (right panel). Bottom row: Light curves
of the SOL2012‐07‐12 flare. Left panel: Soft X‐ray emission observed
by GOES, with high‐energy (blue curve) and low‐energy (red curve)
channels. Right panel: Radio flux density light curves from 2 to
15 GHz recorded by RSTN, and at 45 and 90 GHz (red curve) observed
by POEMAS. The vertical red dashed line represents the approximate
launch time of the associated CME.
]]

== CMEs and Space Weather ==

Each of the three flares was accompanied by a coronal mass ejection
(CME) detected by LASCO/SOHO, and in all three cases the CME was
launched essentially simultaneously with the radio burst onset.
Two of the three events led to geomagnetic storms, as measured
by the
[https://wdc.kugi.kyoto-u.ac.jp/dstdir/ Dst index].
Notably the interaction of the July ICME with the magnetosphere also
triggered [https://en.wikipedia.org/wiki/Aurora aurora australis],
photographed by the crew of the International Space Station on 15 July 2012.

[[File:527f2.png|center|thumb|800px|caption|Figure 1: 
Scatter plots showing the positive correlation between the absolute
minimum Dst geomagnetic index (left) and CME velocity measured from
coronagraph observations (right) with the peak radio flux at 45 GH
Note that the March CME event missed Earth.
]]

== Conclusions ==

The central finding of this study is a consistent positive correlation
between the peak radio flux measured at 45 GHz and a suite of space
weather indicators: GOES flare class, SXR energy, CME velocity and
kinetic energy, ionospheric D-region depression, and geomagnetic
storm severity as quantified by Dst and Kp (Figure 2). The X1.4
event on 12 July 2012 sat at the high end of all these scales
simultaneously producing the brightest millimeter burst (116 SFU
at 45 GHz), the fastest and most energetic CME (884 km/s, 2.7 ×
1031 ergs), the deepest ionospheric depression (9 km), and the
strongest geomagnetic storm (Dst = −139 nT) of the three events.

The magnetic field strength in the gyrosynchrotron-emitting source
(~160–180 G) was essentially the same in all three flares, pointing
to a common magnetic topology. What differentiated the events was
the number of accelerated electrons and the source volume. Moreover,
the spectral index δ, consistently hard (~2.8, hardening toward 2
as each burst progressed), is characteristic of the millimeter-emitting
population and harder than what is typically inferred from
microwave-only studies, reflecting a selection effect at the highest
frequencies.

High-frequency millimeter radio observations thus appear to be a
promising tool for early space weather assessment: they are sensitive
to the most energetic particle populations, they respond on the
same timescale as the flare itself (allowing prediction hours or
even days before a CME arrives), and they correlate well with both
the CME properties and the ultimate geomagnetic impact. POEMAS
recorded 49 solar radio bursts during the 2012–2013 solar maximum,
at least half associated with halo or partial halo CMEs, offering
a valuable archive for extending this type of analysis to a larger
statistical sample.

== Acknowledgment ==

The authors of Ref. [1] and this Nugget are A. Valio, K.F. Lopez, J.L.
Gamonal Valenzuela, R.M. Romero Ramírez, and D.F. da Silva.

== References ==

[1] [https://doi.org/10.1029/2025JA03461 "Space weather impacts of three solar flares observed by the POEMAS telescope at 45 and 90 GHz"]

[2] [http://adsabs.harvard.edu/abs/2004ApJ...603L.121K "A new solar burst spectral component emitting only in the terahertz range:]

[3] [ https://ui.adsabs.harvard.edu/abs/2013SoPh..283..651V "New circular polarization solar telescopes at two millimeter wavelength ranges"]

Space Weather Impact of Three Solar Flares Observed at Millimeter Wavelengths

2026-05-25T20:25:15Z

Hhudson:

{{Infobox Nugget |name = Nugget
|title = Space Weather Impact of Three Solar Flares Observed at Millimeter Wavelengths
|number = 527
|first_author = Adriana VALIO et al.
|publish_date = May 25, 2026
|next_nugget = TBD
|previous_nugget = {{#ask: [[Category:Nugget]] [[RHESSI Nugget Index::526]]}}
}}

== Introduction ==

Solar flares are among the most energetic events in the solar system,
releasing vast amounts of energy across the electromagnetic spectrum
(from radio waves to gamma-rays) in a matter of minutes to hours.
Long-duration events are especially important because their prolonged
magnetic reconnection continuously accelerates particles, pumping
energy into the heliosphere long after the initial impulsive phase
has ended. Understanding the link between the properties of these
flares, the coronal mass ejections (CMEs) launched simultaneously,
and the disturbances caused at Earth is a central challenge of space
weather science.

One key area of observation of these phenomena -- millimeter radio waves -- has not been so well exploited.
The
[https://en.wikipedia.org/wiki/POlarization_Emission_of_Millimeter_Activity_at_the_Sun POEMAS]
telescope fills this key gap by making systematic solar observations at
45 and 90 Ghz (6.6 and 3.3 mm), crucial to understanding the
[https://en.wikipedia.org/wiki/Synchrotron_radiation gyrosynchrotron radiation]
fundamental to flare development.

We used this facility to carry out a detailed multiwavelength analysis (Ref. [1]) of
three long-duration solar flares during the solar maximum period of 2012
(Ref. [1]):
SOL2012-03-02 (M3.3; m4.80)
SOL2012-06-06 (M2.1; m3.07)
SOL2012-07-12 (X1.4; x1.85)
The adjusted ABCMX classes come from
[https://heliowiki.smce.nasa.gov/wiki/index.php/X-ray_Log_Letters] the previous Nugget]
as an experiment here; by either class scheme these events span a factor of 40
in magnitude.
The POEMAS high-frequency observations include measurements of circular
polarization, a key attribute not otherwise available.

== Radio Bursts and Gyrosynchrotron Modelling ==

Each flare was observed in both millimeter emission (POEMAS at 45
and 90 GHz) and microwaves
(the [https://en.wikipedia.org/wiki/STN Radio_Solar_Telescope_Network] at 1–15 GHz).
Combined radio spectra
spanning 5–90 GHz were assembled at four time intervals during each
burst and fitted with a gyrosynchrotron model using a Markov Chain
Monte Carlo (MCMC) algorithm. The fits yield four key physical
parameters: the magnetic field strength Bmag, the total number of
accelerated electrons Ne, the source size a, and the
spectral index of the electron energy distribution δ.

A main result is that all three events return remarkably similar
magnetic field strengths of about 160–180 G, despite the enormous
differences in overall flare energy.
This suggests a common coronal
magnetic configuration for these gyrosynchrotron-emitting sources,
and that what distinguishes powerful from weaker events is primarily
the number of electrons accelerated and the spatial extent of the
emitting region, not the field strength itself.
SOL2012-07-12 (X1.4; Figure 1)
had a source diameter roughly 3–6 times larger than the
other events and accelerated 6–13 times more electrons.
The spectral index δ was about 2.8 across all events,
harder than the typical microwave
range of 3–5.
This reflects a bias toward energetic events at millimeter
wavelengths, where only hard-spectrum flares produce detectable
flux at 90 GHz. In all three cases δ hardened further as each burst
progressed, reaching values near 2 by the end of the event.
The June and July flares also showed flux at 90 GHz exceeding that at
45 GHz, a "sub-THz component" previously reported by Ref. [2]
and indicating an additional emission mechanism at the
highest frequencies, distinct from the standard gyrosynchrotron
component.

[[File:527f1.png|center|thumb|700px|caption|Figure 1: 
Top row: Extreme ultraviolet (EUV) images captured by the Atmospheric
Imaging Assembly (AIA) instrument onboard the Solar Dynamics
Observatory (SDO) satellite, showing the SOL2012‐07‐12 flare at 171 Å
(left panel) and 304 Å (right panel). Bottom row: Light curves
of the SOL2012‐07‐12 flare. Left panel: Soft X‐ray emission observed
by GOES, with high‐energy (blue curve) and low‐energy (red curve)
channels. Right panel: Radio flux density light curves from 2 to
15 GHz recorded by RSTN, and at 45 and 90 GHz (red curve) observed
by POEMAS. The vertical red dashed line represents the approximate
launch time of the associated CME.
]]

== CMEs and Space Weather ==

Each of the three flares was accompanied by a coronal mass ejection
(CME) detected by LASCO/SOHO, and in all three cases the CME was
launched essentially simultaneously with the radio burst onset.
Two of the three events led to geomagnetic storms, as measured
by the
[https://wdc.kugi.kyoto-u.ac.jp/dstdir/ Dst index].
Notably the interaction of the July ICME with the magnetosphere also
triggered [https://en.wikipedia.org/wiki/Aurora aurora australis],
photographed by the crew of the International Space Station on 15 July 2012.

[[File:527f2.png|center|thumb|800px|caption|Figure 1: 
Scatter plots showing the positive correlation between the absolute
minimum Dst geomagnetic index (left) and CME velocity measured from
coronagraph observations (right) with the peak radio flux at 45 GH
Note that the March CME event missed Earth.
]]

== Conclusions ==

The central finding of this study is a consistent positive correlation
between the peak radio flux measured at 45 GHz and a suite of space
weather indicators: GOES flare class, SXR energy, CME velocity and
kinetic energy, ionospheric D-region depression, and geomagnetic
storm severity as quantified by Dst and Kp (Figure 2). The X1.4
event on 12 July 2012 sat at the high end of all these scales
simultaneously producing the brightest millimeter burst (116 SFU
at 45 GHz), the fastest and most energetic CME (884 km/s, 2.7 ×
1031 ergs), the deepest ionospheric depression (9 km), and the
strongest geomagnetic storm (Dst = −139 nT) of the three events.

The magnetic field strength in the gyrosynchrotron-emitting source
(~160–180 G) was essentially the same in all three flares, pointing
to a common magnetic topology. What differentiated the events was
the number of accelerated electrons and the source volume. Moreover,
the spectral index δ, consistently hard (~2.8, hardening toward 2
as each burst progressed), is characteristic of the millimeter-emitting
population and harder than what is typically inferred from
microwave-only studies, reflecting a selection effect at the highest
frequencies.

High-frequency millimeter radio observations thus appear to be a
promising tool for early space weather assessment: they are sensitive
to the most energetic particle populations, they respond on the
same timescale as the flare itself (allowing prediction hours or
even days before a CME arrives), and they correlate well with both
the CME properties and the ultimate geomagnetic impact. POEMAS
recorded 49 solar radio bursts during the 2012–2013 solar maximum,
at least half associated with halo or partial halo CMEs, offering
a valuable archive for extending this type of analysis to a larger
statistical sample.

== Acknowledgment ==

The authors of Ref. [1] and this Nugget are A. Valio, K.F. Lopez, J.L.
Gamonal Valenzuela, R.M. Romero Ramírez, and D.F. da Silva.

== References ==

[1] [https://doi.org/10.1029/2025JA03461 "Space weather impacts of three solar flares observed by the POEMAS
telescope at 45 and 90 GHz"]

[2] [http://adsabs.harvard.edu/abs/2004ApJ...603L.121K "A new solar burst spectral component emitting only in the terahertz range:]

[3] [ https://ui.adsabs.harvard.edu/abs/2013SoPh..283..651V "New circular polarization solar telescopes at two millimeter wavelength ranges"]

SolarNuggets

2026-05-25T19:24:44Z

Hhudson: Added 527

Welcome to the [[SolarNuggets]] collection, which extends the series of [[RHESSI]] Nuggets. The following is a time-ordered list of the latest Nuggets added to the HelioWiki. An [[:Category:Nugget|alphabetical list of the SolarNuggets]] is also available as well as [[:Category:RHESSI Nugget List|yearly lists]]. One can search on author, topic, IAU flare identifier, etc.). We welcome volunteer authors - please see our page of [[Help:For_Authors| help for authors]] or just send an email to the Curator at (hugh.hudson@glasgow.ac.uk).

{{Nugget Badge
|title = Space Weather Impact of Three Solar Flares Observed at Millimeter Wavelengths
|number = 527
|first_author = Adriana VALIO et al.
||publish_date = 25 May 2026
|description = Radio mm waves tell an interesting new story
|image=Icon527.png}}

{{Nugget Badge
|title = X-ray Log Letters‎‎
|number = 526
|first_author = Hugh HUDSON
|second_author = and Ed CLIVER
||publish_date = 18 May 2026
|description = Replacing ..ABCMX.. with a new - comprehensive and quantitative - "QSabcmxyz" catalog
|image=Icon526.png}}

{{Nugget Badge
|title = How Extreme Can Solar Flares Get? A Statistical View‎‎
|number = 525
|first_author = Lapo Ceccarelli
|second_author = and Daniela CASTRO-CAMILO
||publish_date = 4 May 2026
|description = A proper statistical treatment of the prospects for an extreme solar flare event
|image=Icon525.png}}

{{Nugget Badge
|title = Observations of Slow Elemental Abundance Decay in Association to CME
|number = 524
|first_author = Saara TAKALA
||publish_date = 27 April 2026
|description = Soft X-ray spectroscopy tracks coronal abundance variations associated with a CME
|image=Icon524.png}}

{{Nugget Badge
|title = An Unusual Long-Lived Radio Burst Oscillating in Frequency
|number = 523
|first_author = Marian KARLICKÝ,
|second_author = Robert SYCH and Alena ZEMANOVÁ
||publish_date = 20 April 2026
|description = Remarkable decimetric signatures of structured outflows from a flaring active region
|image=Icon523.png}}

{{Nugget Badge
|title = Lateral Deformation of Large-scale Coronal Mass Ejections during the Transition from Nonradial to Radial Propagation
|number = 522
|first_author = Huidong HU
||publish_date = 13 April 2026
|description = Coronal mass ejections can begin their trajectory highly tilted to the vertical, but then straighten out
|image=Icon522.png}}

{{Nugget Badge
|title = Can EUV Power-Spectral Indices Reveal Imminent Solar Flares?
|number = 521
|first_author = Sihui ZHONG,
|second_author = Dmitrii KOLOTKOV and Valery M. NAKARIAKOV
||publish_date = 6 April 2026
|description = A new flare-precursor observable - power spectra
|image=Icon521.png}}

{{Nugget Badge
|title = How energetic can solar flares become?
|number = 520
|first_author = Natalie KRIVOVA
||publish_date = 31 March 2026
|description = The history of active-region areas suggests the possibility of solar superflares
|image=Icon520.png}}

{{Nugget Badge
|title = Hinode EIS Observations of Plasma Composition Evolution and Radiative Cooling of Flare Loops
|number = 519
|first_author = Teodora MIHĂILESCU,
|second_author = Peter YOUNG et AL.
||publish_date = 16 March 2026
|description = Higher FIP bias than expected in some flare loops, a diagnostically interesting result
|image=Icon519.png}}

{{Nugget Badge
|title = When Magnetic Field Lines Stretch, Snap, and Expand: A New Look at Solar Flares with L-maps
|number = 518
|first_author = Maria KAZACHENKO,
|second_author = Yuhong FAN and Andrey AFANASYEV
||publish_date = 9 March 2026
|description = A clever new tool tracks magnetic connectivity (and energy) during flare/CME occurrence
|image=Icon518.png}}

{{Nugget Badge
|title = Observational Evidence Linking Loop Length and Thermal/Nonthermal Peak Timing in Solar Flares
|number = 517
|first_author = Solomon PERRIYIL
||publish_date = 23 February 2026
|description = Clear evidence for the universality of the physics behind the Neupert Effect
|image=Icon517.png}}

{{Nugget Badge
|title = A fine-scale bright kernel captured by Hi-C 3 in the post-maximum phase of an M-class solar flare
|number = 516
|first_author = Sanjiv TIWARI
||publish_date = 9 February 2026
|description = The Hi-C rocket catches an extremely compact brightening in late-phase flare ribbon development
|image=Icon516.png}}

{{Nugget Badge
|title = On the Relationship Between Nanoflare Energy and Delay in the Closed Solar Corona
|number = 515
|first_author = Shanwlee SOW MONDAL et al.
||publish_date = 19 January 2026
|description = Nanoflaring implies energy storage and sudden release, suggesting correlation between event energy and its timing
|image=Icon515.png}}

{{Nugget Badge
|title = Fine structures in solar flare ribbons
|number = 514
|first_author = Jonas THOEN FABER
||publish_date = 12 January 2026
|description = Elongated "riblets" commonly rise out of flare ribbons, and have characteristic Doppler shifts
|image=Icon514.png}}

{{Nugget Badge
|title = The M- and X-class White-light Flares in Super Active Region NOAA 13664/13697
|number = 513
|first_author = Zhichen JING
|second_author = and Ying LI
|publish_date = 5 January 2026
|description = "Super" active regions have relatively more frequent X-class flares, which correlate well with visible continuum (white-light flare) emission
|image=Icon513.png}}

{{Nugget Badge
|title = Iron Fluorescence in X-class Solar Flares
|number = 512
|first_author = Abhilash SARWADE
|publish_date = 8 December 2025
|description = A new spectroscopic capability for Iron K-alpha fluorescence
|image=Icon512.png}}

{{Nugget Badge
|title = Sun-as-a-star Analysis of a Solar Eruption Source Region Using H-alpha Spectroscopic Observations from CHASE
|number = 510
|first_author = Xiaofeng LIU
|second_author = and Yijun HOU
|publish_date = 24 November 2025
|description = Sun-as-a-star observations help to translate solar/stellar processes
|image=Icon5010.png}}

{{Nugget Badge
|title = On the Origin of Solar Long-Duration Gamma-Ray Flares‎‎‎‎
|number = 509
|first_author = Alessandro BRUNO
|publish_date = 3 November 2025
|description = Do we really need a CME to produce a long-duration solar gamma-ray event?
|image=Icon509.png}}

{{Nugget Badge
|title = FAI and GOES eclipses‎‎
|number = 508
|first_author = Hugh HUDSON
|publish_date = 20 October 2025
|description = Flare anticipation via FAI may have problems during GOES eclipses, which are really interesting in their own right
|image=Icon508.png}}

{{Nugget Badge
|title = The EUV Late Phase‎
|number = 507
|first_author = Sascha ORNIG
|publish_date = 13 October 2025
|description = Basic comparative statistics of the ELP, a distinct flare phenomenon
|image=Icon507.png}}

{{Nugget Badge
|title = Time evolution of flare-accelerated electrons using the warm-target model‎
|number = 506
|first_author = Debesh BHATTACHARJEE
|publish_date = 6 October 2025
|description = Considering a "warm" thick target allows flare-accelerated electrons to be treated self-consistently
|image=Icon506.png}}

{{Nugget Badge
|title = SOLSTICE observes flare Doppler shifts in Si III
|number = 505
|first_author = Luke MAJURY
|publish_date = 30 September 2025
|description = A rarely used database suggests prograde-flow Doppler shifts in flaring plasmas
|image=Icon505.png}}

{{Nugget Badge
|title = Flare Phases and the Earth's Ionospheric Response
|number = 504
|first_author = Susanna BEKKER
|publish_date = 16 September 2025
|description = A flare's "EUV late phase" is surprisingly geoeffective
|image=Icon504.png}}

{{Nugget Badge
|title = Neupertianity
|number = 503
|first_author = Hugh HUDSON
|publish_date = 25 August 2025
|description = It's hard to avoid the Neupert Effect
|image=Icon503.png}}

{{Nugget Badge
|title = Synchrotron Radiation and the Foundations for a Cosmic Bridge
|number = 502
|first_author = Immanuel JEBARAJ
|publish_date = 11 August 2025
|description = Gyrosynchrotron radiation in shocks: a cosmic connection
|image=Icon502.png}}

{{Nugget Badge
|title = The Aulanier Effect: drifting footpoints of CME flux ropes
|number = 501
|first_author = Jaroslav DUDÍK,
|second_author = Juraj LÖRINČÍK and Brigitte SCHMIEDER
|publish_date = 21 July 2025
|description = The breakthrough to 3D flare physics: the Aulanier Effect
|image=Icon501.png}}

{{Nugget Badge
|title = Five Hundred Nuggets
|number = 500
|first_author = Hugh HUDSON
|publish_date = 14 July 2025
|description = A milestone
|image=Icon169.png}}

{{Nugget Badge
|title = Quasiperiodic Pulsations in the Balmer Continuum in an X-class Solar White-light Flare
|number = 499
|first_author = De-Chao SONG et al.
|publish_date = 30 June 2025
|description = QPP in the Balmer continuum: the powerful heartbeat of a flare
|image=Icon499.png}}

{{Nugget Badge
|title = High-Resolution Observations of a C3 class White-Light Flare
|number = 498
|first_author = Zhe XU and
|second_author = Xiaoli YAN
|publish_date = 16 June 2025
|description = A compact white-light flare with vortical motions (and hard X-rays)
|image=Icon498.png}}

{{Nugget Badge
|title = The Sun's open-closed flux boundary and the origin of the slow solar wind
|number = 497
|first_author = Chloe WILKINS and
|second_author = David PONTIN
|publish_date = 26 May 2025
|description = Identifying the solar sources of slow solar wind
|image=Icon497.png}}

{{Nugget Badge
|title = Delay of Near-Relativistic Electrons
|number = 496
|first_author = Grant MITCHELL
|publish_date = 19 May 2025
|description = Parker Solar Probe solves an old mystery about type III bursts
|image=Icon496.png}}

{{Nugget Badge
|title = A Multi-Site Telescope for Multi-Height for Synoptic Observations
|number = 495
|first_author = Fallon KONOW
|publish_date = 11 May 2025
|description = A new synoptic network for observations at multiple wavelengths
|image=Icon495.png}}

{{Nugget Badge
|title = On turbulent magnetic reconnection: fast and slow mean steady-states
|number = 494
|first_author = Sage STANISH
|second_author = and David MacTAGGART
|publish_date = 28 April 2025
|description = In a turbulent medium, magnetic reconnection has two limiting domains
|image=Icon494.png}}

{{Nugget Badge
|title = Quasi-Periodic Pulsations in Ionospheric TEC and Flare EUV
|number = 493
|first_author = Aisling O'HARE
|publish_date = 21 April 2025
|description = The Earth's ionosphere reflects QPPs, with a small delay
|image=Icon493.png}}

{{Nugget Badge
|title = Metis observations of Alfvenic outflows driven by interchange reconnection in a pseudostreamer
|number = 492
|first_author = Paolo ROMANO and the Metis team
|publish_date = 7 April 2025
|description = Exactly as predicted by numerical simulations... a rare coup
|image=Icon492.png}}

{{Nugget Badge
|title = Solar Rollercoaster: looping-the-loop in the solar corona
|number = 491
|first_author = Mohamed NEDAL et al.
|publish_date = 31 March 2025
|description = Large-scale helical motion in the flare/CME SOL2024-05-14
|image=Icon491.png}}

{{Nugget Badge
|title = Proton Beam Energy Deposition as a Mechanism of Deep Photospheric Heating
|number = 490
|first_author = Samuel GRANOVSKY
|second_author = and Alexander KOSOVICHEV
|publish_date = 17 March 2025
|description = Evidence for proton beams in white-light flares
|image=Icon490.png}}

{{Nugget Badge
|title = New insights into the proton precipitation sites in solar flares
|number = 489
|first_author = Andrea Francesco BATTAGLIA
|second_author = and Säm KRUCKER
|publish_date = 17 February 2025
|description = There is no detectable difference in proton and electron foopoint locations after all
|image=Icon489.png}}

{{Nugget Badge
|title = Solar Gamma-Ray Evidence for a Distinct Population of MeV Flare-Accelerated Electrons
|number = 488
|first_author = Gerry SHARE
|second_author =
|publish_date = 10 February 2025
|description = Relativistic electrons in solar flares newly recognized as a distinct process
|image=Icon488.png}}

{{Nugget Badge
|title = From Chromospheric Evaporation to Coronal Rain: An Investigation of the Mass and Energy Cycle of a Flare‎
|number = 487
|first_author = Seray &Scedil;AHIN
|second_author = and Patrick ANTOLIN
|publish_date = 3 February 2025
|description = A first quantitative comparison of flare evaporation and coronal rain
|image=Icon487.png}}

{{Nugget Badge
|title = Energetic neutral atoms detected in the large solar energetic particle event of February 2022‎
|number = 486
|first_author = Christina COHEN
|second_author =
|publish_date = 20 January 2025
|description = Only the second direct observation of high-energy neutral atoms from the Sun
|image=Icon486.png}}

{{Nugget Badge
|title = Magnetic topology of quiet-Sun Ellerman bombs and associated ultraviolet brightenings‎
|number = 485
|first_author = Aditi BHATNAGAR
|second_author =
|publish_date = 6 January 2025
|description = Tiny "Ellerman Bombs" occur all across the solar surface, with differences
|image=Icon485.png}}

{{Nugget Badge
|title = Unveiling CME Dynamics: Rare Rotations of CMEs in the Heliosphere
|number = 484
|first_author = Sandeep KUMAR and
|second_author = Nandita SRIVASTAVA
|publish_date = 30 December 2024
|description = CMEs usually do not show additional rotation as they move though the heliosphere
|image=Icon484.png}}

{{Nugget Badge
|title = Spatial and Spectral Evolution of Microwave and X-Ray Sources During the Limb Flare SOL2023-02-05
|number = 483
|first_author = Yulia N. SHAMSUTDINOVA
|publish_date = 23 December 2024
|description = Rare microwave imaging spectroscopy of a hot-onset precursor event
|image=Icon483.png}}

{{Nugget Badge
|title = High-resolution observational analysis of flare ribbon fine structures
|number = 482
|first_author = Jonas THOEN FABER
|publish_date = 16 December 2024
|description = Spatially periodic fine structures in flare ribbons reveal current-sheet tearing
|image=Icon482.png}}

{{Nugget Badge
|title = Advection and super-diffusive expansion as the model of flare accelerated electron transport in type III solar radio bursts
|number = 481
|first_author = Eduard KONTAR
|publish_date = 9 December 2024
|description = Sturrock's dilemma resolved
|image=Icon481.png}}

{{Nugget Badge
|title = Faraday's Law in Solar Flares: A Cautionary Message
|number = 480
|first_author = Michael FARADAY
|publish_date = 2 December 2024
|description = We must not forget the global implications of Faraday's Law
|image=Icon480.png}}

{{Nugget Badge
|title = Remarkable NUV Spectrum of an M-star Megaflare
|number = 479
|first_author = Adam KOWALSKI
|publish_date = 25 November 2024
|description = Remarkable NUV spectra from an HST stellar flare
|image=Icon479.png}}

{{Nugget Badge
|title = Revised Point-Spread Functions of AIA and their effect on DEM analyses
|number = 478
|first_author =Stefan HOFMEISTER,
|second_author = Daniel Wolf SAVIN, and Michael HAHN
|publish_date = 18 November 2024
|description = Substantial revisions of the AIA point-response functions
|image=Icon478.png}}

{{Nugget Badge
|title = How much of the energy in flare-accelerated electrons reaches the chromosphere?
|number = 477
|first_author = Meriem ALAOUI
|second_author = and Gordon HOLMAN
|publish_date = 11 November 2024
|description = Keeping flare-accelerated electrons out of the chromosphere
|image=Icon477.png}}

{{Nugget Badge
|title = Spatially resolved plasma composition evolution in a solar flare
|number = 476
|first_author = Andy S. H. TO
|publish_date = 4 November 2024
|description = Reconnection outflow feeds abundance variations
|image=Icon476.png}}

{{Nugget Badge
|title = HOPE during high activity
|number = 475
|first_author = Hugh HUDSON
|second_author = and Alphonse STERLING
|publish_date = 28 October 2024
|description = Hot onsets appear even in the most active solar conditions
|image=Icon475.png}}

{{Nugget Badge
|title = Simulated heliospheric electron spectra show sensitivity to plasma properties of a source region in the flaring corona
|number = 474
|first_author = Ross PALLISTER
|second_author = and Natasha JEFFREY
|publish_date = 21 October 2024
|description = Getting closer to an understanding of how solar energetic particles "escape"
|image=Icon474.png}}

{{Nugget Badge
|title = An extremely complex active region with very strong non-neutralized electric currents
|number = 473
|first_author = Ioannis KONTOGIANNIS
|publish_date = 14 October 2024
|description = Large non-neutralized electric currents flow through the active-region corona
|image=Icon473.png}}

{{Nugget Badge
|title = An X9 flare and its huge crochet (SFE)
|number = 472
|first_author = Hugh HUDSON
|publish_date = 7 October 2024
|description = The geomagnetic effect (SFE/crochet) that will calibrate the Carrington flare
|image=Icon472.png}}

{{Nugget Badge
|title = All microflares that accelerate electrons to high energies are rooted in sunspots
|number = 471
|first_author = Andrea Francesco BATTAGLIA
|publish_date = 30 September 2024
|description = Microflares with hard X-ray spectra are a well-defined class, and invariably have one footpoint embedded in a sunspot
|image=Icon471.png}}

{{Nugget Badge
|title = The warm-target model and kappa distributions
|number = 470
|first_author = Yingjie LUO
|publish_date = 16 September 2024
|description = A self-consistent treatment of non-thermal electron spectra points to kappa distributions
|image=Icon470.png}}

{{Nugget Badge
|title = Is there HOPE for Hyder flares...
|number = 468
|first_author = Hugh HUDSON
|publish_date = 15 March 2024
|description = Filament eruptions/Hyder flares/disparitions brusques may all show HOPE
|image=Icon468.png}}

{{Nugget Badge
|title = Sun-as-a-star Analysis of the M8.7 Flare on 2022 October 2 Using H-alpha and EUV Spectra Taken by SMART/SDDI and SDO/EVE
|number = 467
|first_author = Takato OTSU
|publish_date = 19 February 2024
|description = Whole-Sun spectroscopic observations can readily detect ejecta
|image=Icon467.png}}

{{Nugget Badge
|title = Unexpected Asymmetry in GeV Emission
|number = 466
|first_author = Bruno ARSIOLI and Elena ORLANDO
|publish_date = 15 January 2024
|description = The high-energy solar gamma radiation shows inexplicable but fascinating properties
|image=Icon466.png}}

{{Nugget Badge
|title = When it rippled in one place and exploded in another
|number = 465
|first_author = Ivan ZIMOVETS
|publish_date = 25 December 2023
|description = Pulsations precede a flare, but seem unrelated
|image=Icon465.png}}

{{Nugget Badge
|title = Solar flares: evaporation and simulation‎
|number = 464
|first_author = Malcolm DRUETT
|publish_date = 18 December 2023
|description = Fitting beam electrons into multi-dimensional models
|image=Icon464.png}}

{{Nugget Badge
|title = Pre-impulsive and Impulsive Phases of the March 28, 2022 Sub-Terahertz Flare
|number = 463
|first_author = Galina G. MOTORINA
|publish_date = 11 December 2023
|description = A flare with an increasing sub-THz spectrum and sub-THZ precursor information
|image=Icon463.png}}

{{Nugget Badge
|title = Coronal Bright Points
|number = 462
|first_author = Daniel NÓBREGA-SIVERIO
|publish_date = 27 November 2023
|description = Bright EUV rowel-like structures can result from null-point reconnection
|image=Icon462.png}}

{{Nugget Badge
|title = Aurora-like Radio Emission from a Sunspot
|number = 461
|first_author = Sijie YU
|publish_date = 20 November 2023
|description = Maser action above a sunspot
|image=Icon461.png}}

{{Nugget Badge
|title = Search for a Flare Anticipation Index (FAI)
|number = 460
|first_author = Hugh HUDSON
|second_author = and Jim McTiernan
|publish_date = 13 November 2023
|description = Quantifying flare precursors on a few-minute time scale
|image=Icon460.png}}

{{Nugget Badge
|title = Bouncing motions of fast electrons using Nobeyama Radioheliograph
|number = 459
|first_author = Keitarou MATSUMOTO
|publish_date = 6 November 2023
|description = Solar evidence for conservation of second adiabatic invariant in particle motion
|image=Icon459.png}}

{{Nugget Badge
|title = Impact of nanoflare heating in the lower solar atmosphere
|number = 458
|first_author = Helle BAKKE
|publish_date = 30 October 2023
|description = The behavior of nanoflare fast electrons in Bifrost models
|image=Icon458.png}}

{{Nugget Badge
|title = Precise timing of flare footpoint sources from mid-infrared observations‎
|number = 457
|first_author = Paulo SIMÕES et al.
|publish_date = 23 October 2023
|description = Mid-IR observations at high spatial and high temporal resolution: Conjugacy
|image=Icon457.png}}

{{Nugget Badge
|title = The Greatest GOES Flares‎
|number = 456
|first_author = Hugh HUDSON
|second_author = and Ed CLIVER
|publish_date = 25 September 2023
|description = The greatest GOES events, re-analyzed, fall short of expectations
|image=Icon456.png}}

{{Nugget Badge
|title = Introducing SunSketcher
|number = 455
|first_author = Hugh HUDSON
|second_author = and Gordon EMSLIE
|publish_date = 11 September 2023
|description = Galloping towards roundup in the 2024 total solar eclipse
|image=Icon455.png}}

{{Nugget Badge
|title = TeV Gamma rays from the Quiescent Sun
|number = 454
|first_author = Mehr Un NISA
|second_author = and John BEACOM
|publish_date = 21 August 2023
|description = Solar photons at unprecedented high energies
|image=Icon454.png}}

{{Nugget Badge
|title = Temporal and Spatial Characteristics of Hard X-Ray Sources in Flare Model with Vertical Current Sheet
|number = 453
|first_author = Alexander SHABALIN, Eugenia OVCHINNIKOVA,
|second_author = and Yuri CHARIKOV
|publish_date = 7 August 2023
|description = Modeling betatron acceleration in current-sheet development.
|image=Icon453.png}}

{{Nugget Badge
|title = Spatial Distribution of Magnetic Reconnection Rate in an M6.5 Solar Flare
|number = 452
|first_author = Ju JING
|publish_date = 12 June 2023
|description = Linking hard X-rays to high-resolution images that show reconnection rates.
|image=Icon452.png}}

{{Nugget Badge
|title = Statistical study of Type III bursts and associated HXR emissions
|number = 451
|first_author = Nicole VILMER and Tomin JAMES
|publish_date = 29 May 2023
|description = Linking electron populations escaping from the Sun with those that RHESSI detects.
|image=Icon451.png}}

{{Nugget Badge
|title = Solar flare hard X-rays from the anchor points of an eruptive filament
|number = 450
|first_author = Muriel STIEFEL
|publish_date = 15 May 2023
|description = A rare "four-ribbon" flare has been detected in hard X-rays.
|image=Icon450.png}}

{{Nugget Badge
|title = Did a Solar Flare Accelerate all the Ambient Electrons in the Coronal Acceleration Region?...
|number = 449
|first_author = Gordon EMSLIE, Eduard KONTAR,
|second_author = Galina MOTORINA, and Brian DENNIS
|publish_date = 1 May 2023
|description = Considering SOL2017-09-10, probably not.
|image=Icon449.png}}

{{Nugget Badge
|title = Diagnostics of Spatially-Extended Turbulent Acceleration and Transport
|number = 448
|first_author = Morgan STORES
|publish_date = 24 April 2023
|description = Drilling down into the detailed structure of solar-flare energy release by including turbulence with particle acceleration.
|image=Icon448.png}}

{{Nugget Badge
|title = RHESSI's Re-entry
|number = 447
|first_author = Pascal SAINT-HILAIRE and
|second_author = Hugh HUDSON
|publish_date = 17 April 2023
|description = The final demise of RHESSI is this week
|image=Icon447.png}}

{{Nugget Badge
|title = A Glasgow geomagnetic observation of a solar flare
|number = 446
|first_author = Hugh HUDSON, John MALONE-LEIGH,
|second_author = Graham WOAN, and Chris OSBORNE
|publish_date = 13 March 2023
|description = Irish and Scottish geomagnetic observatories see a crochet much like that of the Carrington event
|image=Icon_446.png}}

{{{Nugget Badge
|title = Particle Acceleration in Two Coronal Jets
|number = 445
|first_author = Yixian ZHANG
|publish_date = 27 February 2023
|description = Coronal jets with hard X-ray sources at disjoint locations
|image=Icon445.png}}

{{Nugget Badge
|title = The Curious First Sunquake of Solar Cycle 25‎
|number = 444
|first_author = Alexander KOSOVICHEV
|publish_date = 13 February 2023
|description = A double whammy: two distinct sunquakes from SOL2022-05-10.
|image=Icon444.png}}

{{Nugget Badge
|title = Hard X-ray Pulsations via Gaussian Decomposition
|number = 443
|first_author = Hannah COLLIER and Laura HAYES
|publish_date = 30 January 2023
|description = Flare hard X-ray time variations decomposed objectively
|image=Icon443.png}}

{{Nugget Badge
|title = A possible coronal magnetic flare precursor
|number = 442
|first_author = Enrico LANDI
|publish_date = 16 January 2023
|description = Novel measurements of the coronal magnetic field may help with flare prediction
|image=Icon442.png}}

{{Nugget Badge
|title = A slow HOPE with microwave context
|number = 441
|first_author = Hugh HUDSON
|publish_date = 12 December 2022
|description = A new microwave facility at Chashan Observatory, and a prototypical HOPE
|image=Icon441.png}}

{{Nugget Badge
|title = Rapid variations of Si IV spectra in a flare observed by IRIS at a sub-second cadence
|number = 440
|first_author = Juraj LÖRINČÍK
|publish_date = 14 November 2022
|description = Transition-region lines in a flare have a Doppler component revealing quasi-periodic pulsations
|image=Icon440.png}}

{{Nugget Badge
|title = A Significant Sudden Ionospheric Disturbance Associated with a Massive Gamma-ray Burst
|number = 439
|first_author = Laura HAYES and Peter GALLAGHER
|publish_date = 31 October 2022
|description = A first SID observed in broad daylight, from a source far far away
|image=Icon439.png}}

{{Nugget Badge
|title = Effects of Coronal Structures on the Dynamics of the Global Coronal Wave of SOL2017-09-10‎
|number = 438
|first_author = Huidong HU, Ying D. LIU, and Bei ZHU
|publish_date = 17 October 2022
|description = The amazing global coronal wave of SOL2017-09-10 wrapped around the whole Sun, and displayed transmission and reflection at both polar coronal holes
|image=Icon438.png}}

{{Nugget Badge
|title = KW-Sun: The Konus-Wind Solar Flare Database in Hard X-Ray and Soft Gamma-Ray Ranges
|number = 437
|first_author = Alexandra LYSENKO
|publish_date = 26 September 2022
|description = An unrivaled hard X-ray and gamma-ray database is entering its third activity maximum
|image=Icon437.png}}

{{Nugget Badge
|title = First Detection of Kink Oscillations with Solar Orbiter
|number = 436
|first_author = Sihui ZHONG et al.
|publish_date = 19 September 2022
|description = SolO sees coronal oscillations as well as AIA can, and even better
|image=Icon436.png}}

{{Nugget Badge
|title = Energetic Neutral Hydrogen from Large Solar Flares
|number = 435
|first_author = Glenn MASON
|publish_date = 6 September 2022
|description = A rediscovered data treasury reveals the occurrence of many flare/CME events producing solar high-energy neutral atoms
|image=Icon435.png}}

{{Nugget Badge
|title = Fifty-year Anniversary of the First Detection of Gamma rays from a Solar Flare
|number = 434
|first_author = Jim Ryan,
|second_author = Brian Dennis, and Phil Dunphy
|publish_date = 8 August 2022
|description = The rich astrophysics of gamma-ray astronomy began with solar observations fifty years ago
|image=Icon434.png}}

{{Nugget Badge
|title = Fast Prograde Flows in Solar Active Regions
|number = 433
|first_author = Hugh HUDSON
|publish_date = 25 July 2022
|description = Unexpected, unpredicted, and not modeled yet - weird flows in hot active-region loops
|image=Icon433.png}}

{{Nugget Badge
|title = Undetected Minority-polarity Flux, Moss, and Coronal Heating
|number = 432
|first_author = Yi-Ming WANG
|publish_date = 11 July 2022
|description = There's plenty of room in "unipolar" active regions for both polarities, and there is good evidence for them
|image=Icon432.png}}

{{Nugget Badge
|title = Thermal/Nonthermal with MinXSS and RHESSI
|number = 431
|first_author = Shunsaku NAGASAWA
|publish_date = 13 June 2022
|description = Time-domain studies of improved X-ray spectra reveal a "super-hot' component
|image=Icon431.png}}

{{Nugget Badge
|title = Sun-as-a-star spectroscopic observations of the line-of-sight velocity of a solar eruption on October 28, 2021
|number = 430
|first_author = Yu XU
|second_author = and Hui TIAN
|publish_date = 30 May 2022
|description = The observation of the full 3d velocity of a CME, for an anniversary event
|image=Icon430.png}}

{{Nugget Badge
|title = Carl Størmer
|number = 429
|first_author = Hugh HUDSON
|second_author = and Lyndsay FLETCHER
|publish_date = 15 April 2022
|description = Størmer and the theory of trapping in loops
|image=Icon429.png}}

{{Nugget Badge
|title = Solar Hard X-rays with Insight
|number = 428
|first_author = Wei WANG
|second_author = and Ping ZHANG
|publish_date = 21 March 2022
|description = A spectacular limb flare introduces Insight/HXMT, a new observational resource
|image=Icon428.png}}

{{Nugget Badge
|title = Probing chromospheric current sheets using SST and ALMA co-observations
|number = 427
|first_author = João da SILVA SANTOS
|publish_date = 21 February 2022
|description = Emerging magnetic flux appears in ALMA images reflecting coronal current sheets
|image=Icon427.png}}

{{Nugget Badge
|title = A demonstration of STIX hard X-ray imaging spectroscopy capabilities for an X-class flare (SOL2021-10-28)
|number = 426
|first_author = Andrea BATTAGLIA, Hannah COLLIER,
|second_author = and Säm KRUCKER
|publish_date = 7 February 2022
|description = STIX imaging of an X-class flare marks its success
|image=Icon426.png}}

{{Nugget Badge
|title = A solar flare driven by thermal conduction observed in mid-infrared
|number = 425
|first_author = Guillermo GIMÉNEZ de CASTRO
|publish_date = 24 January 2022
|description = Strong 10-micron emission from a GOES C2 flare suggests conductive heating
|image=Icon425.png}}

{{Nugget Badge
|title = Disk Occultation of a Lopsided Sun‎
|number = 424
|first_author = Hugh HUDSON,
|second_author = Stephen WHITE and Säm KRUCKER
|publish_date = 10 January 2022
|description = Observing a spotless Sun can enable observations of the faint corona.
|image=Icon424.png}}

{{Nugget Badge
|title = Resolving two distinct thermal X-ray components in a compound solar flare
|number = 423
|first_author = Zhenjun ZHOU
|second_author = and Rui LIU
|publish_date = 28 December 2021
|description = Superhot coronal sources may be independent loop systems
|image=Icon423.png}}

{{Nugget Badge
|title = Bridging solar flares to coronal mass ejections
|number = 422
|first_author = Markus ASCHWANDEN
|publish_date = 14 December 2021
|description = The Neupert effect allows us to trace coronal mass ejections seamlessly
|image=Icon422.png}}

{{Nugget Badge
|title = The Jakimiec Diagnostic Diagram
|number = 421
|first_author = Hugh HUDSON
|publish_date = 29 November 2021
|description = The joint variation of GOES temperature and emission measure discloses new features via an old tool
|image=Icon421.png}}

{{Nugget Badge
|title = First look at ALMA/HInode/IRIS microflares
|number = 420
|first_author = Toshifumi SHIMIZU
|second_author = et al.
|publish_date = 8 November 2021
|description = High-resolution ALMA and multiwavelength observations of microflaring
|image=Icon420.png}}

{{Nugget Badge
|title = Thomson scattering near sunspots
|number = 419
|first_author = Pascal Saint-Hilaire
|second_author = et al.
|publish_date = 25 October 2021
|description = Completing the modeling of low-coronal Thomson polarimetry
|image=Icon419.png}}

{{Nugget Badge
|title = A Non-PFSS Global Coronal Model
|number = 418
|first_author = Oliver RICE
|second_author = and Anthony YEATES
|publish_date = 11 October 2021
|description = Modeling as convenient as PFSS but much more realistic
|image=Icon418.png}}

{{Nugget Badge
|title = Manifold Nonthermality
|number = 417
|first_author = Marina BATTAGLIA
|second_author = et al.
|publish_date = 27 September 2021
|description = Even weak flares involve multiple sites of non thermal activity
|image=Icon417.png}}

{{Nugget Badge
|title = X-Rays from a Type I Radio Burst
|number = 416
|first_author = R. RAMESH
|publish_date = 20 September 2021
|description = A first identification of type I radio emission with hot plasma
|image=Icon416.png}}

{{Nugget Badge
|title = Do Hot Onsets Predict Flare Magnitudes?
|number = 415
|first_author = Hugh HUDSON
|publish_date = 30 August 2021
|description = Maybe we can tell how big a flare is going to be from its initial development...
|image=Icon415.png}}

{{Nugget Badge
|title = Confined or Eruptive?
|number = 414
|first_author = Ting LI et al.
|publish_date = 16 August 2021
|description = Increased magnetic flux reduces CME eruptivity
|image=Icon414.png}}

{{Nugget Badge
|title = Impulsive and Gradual Eruptive Gamma Flares and Associated CMEs
|number = 413
|first_author = Alexey STRUMINSKY,
|second_author = Irina GRIGORIEVA and Andrei SADOVSKI
|publish_date = 19 July 2021
|description = Extreme behavior of flare/CME events explained by environment
|image=Icon373.png}}

{{Nugget Badge
|title = The Morphology of Flare Time Profiles
|number = 412
|first_author = Larisa KASHAPOVA
|second_author = et al.
|publish_date = 12 July 2021
|description = Systematic comparison of solar and stellar flaring time profiles
|image=Icon412.png}}

{{Nugget Badge
|title = Flare Pulsation and the Heliosphere
|number = 411
|first_author = Brendan CLARKE
|second_author = et al.
|publish_date = 5 July 2021
|description = Flare pulsations link closely to the distant heliosphere
|image=Icon411.png}}

{{Nugget Badge
|title = STIX, the Hard X-Ray Telescope on board Solar Orbiter
|number = 410
|first_author = Andrea Francesco BATTAGLIA
|second_author = and Säm KRUCKER
|publish_date = 28 June 2021
|description = STIX is operational and producing great data
|image=Icon410.png}}

{{Nugget Badge
|title = Nonequilibrium Ionization of Flare Plasma Observed by Hinode/EIS
|number = 409
|first_author = Shinsuke IMADA
|second_author =
|publish_date = 14 June 2021
|description = Evidence for non-equilibrium ionization in the current sheet of SOL2017-09-10
|image=Icon409.png}}

{{Nugget Badge
|title = Effects of Flares on Solar p-modes
|number = 408
|first_author = Maria-Cristina RABELLO SOARES
|second_author = and Frederic BAUDIN
|publish_date = 26 April 2021
|description = No detectable p-mode amplitude changes due to solar flares
|image=Icon408.png}}

{{Nugget Badge
|title = Subsecond Spikes in Solar Flare X-ray Flux as Seen by Fermi GBM
|number = 407
|first_author =Trevor KNUTH
|second_author = and Lindsay GLESENER
|publish_date = 19 April 2021
|description = A new analysis technique pushes hard X-ray time scales to 0.1 sec or faster
|image=Icon407.png}}

{{Nugget Badge
|title = Negative He 10830 Flare Ribbons and Non-thermal Electrons
|number = 406
|first_author = Graham KERR
|second_author =
|publish_date = 12 April 2021
|description = A 1D radiation hydrodynamics model can explain the dark leading edges of He I flare ribbons
|image=Icon406.png}}

{{Nugget Badge
|title = Tracing the sources of gradual solar energetic particle events
|number = 405
|first_author = David H. BROOKS
|second_author = and Stephanie L. YARDLEY
|publish_date = 29 March 2021
|description = Chemical abundances in SEPs suggest an origin in flare-related moss regions
|image=Icon405.png}}

{{Nugget Badge
|title = The Superflare SOL2017-09-06: from submm to mid-IR
|number = 404
|first_author = Guillermo (Guigue) GIMÉNEZ DE CASTRO
|second_author =
|publish_date = 15 March 2021
|description = Glimpsing the "missing decades" of the flare emission spectrum
|image=Icon404.png}}

{{Nugget Badge
|title = The Neupert Effect Revisited
|number = 403
|first_author = Jiong QIU
|second_author =
|publish_date = 8 March 2021
|description = Two time scales for heating individual flare strands
|image=Icon403.png}}

{{Nugget Badge
|title = FLUKA as a tool for interpreting flare gamma-rays
|number = 402
|first_author = Alec MACKINNON
|second_author =
|publish_date = 1 March 2021
|description = The nuclear physics of solar flares captured in a detailed model
|image=Icon402.png}}

{{Nugget Badge
|title = A Collective Study of 11 NuSTAR Microflares
|number = 401
|first_author = Jessie DUNCAN and
|second_author = Lindsay GLESENER
|publish_date = 22 February 2021
|description = Swarms of NuSTAR micro flares
|image=Icon401.png}}

{{{{Nugget Badge
|title = A Solar FRB
|number = 400
|first_author = Dale GARY and
|second_author = Hugh HUDSON
|publish_date = 15 February 2021
|description = A new frontier in the solar time domain
|image=Icon400.png}}

{{Nugget Badge
|title = Richard Schwartz
|number = 399
|first_author = Brian DENNIS and
|second_author = Hugh HUDSON
|publish_date = 25 January 2021
|description = Remembering a friend and colleague
|image=Icon399.jpg}}

{{Nugget Badge
|title = Observing Solar Flare X-ray Polarization with Prospective CubeSat Missions
|number = 398
|first_author = Natasha JEFFREY
|publish_date = 4 January 2021
|description = The polarization of the solar X-ray spectrum generally remains to be observed
|image=Icon398.png}}

{{Nugget Badge
|title = Solar effects in the local interstellar medium
|number = 397
|first_author = Don GURNETT and
|second_author = Hugh HUDSON
|publish_date = 14 December 2020
|description = Relativistic particle events observed _in situ_ in the interstellar medium
|image=Icon397.png}}

{{Nugget Badge
|title = Investigation of Small-Scale Energy Releases in Hard X-rays with FOXSI
|number = 396
|first_author = Subramania ATHIRAY and
|second_author = Juliana VIEVERING
|publish_date = 7 December 2020
|description = Hard X-rays and high temperatures from the feeblest microflares
|image=Icon396.png}}

{{Nugget Badge
|title = What drives impulsive coronal heating?
|number = 395
|first_author = Pradeep CHITTA
|second_author = et al.
|publish_date = 30 November 2020
|description = Impulsive footpoint emissions suggest magnetic reconnection in the chromosphere
|image=Icon395.png}}

{{Nugget Badge
|title = Probing the solar coronal heating function with slow magnetoacoustic waves
|number = 394
|first_author = Dmitrii KOLOTKOV
|second_author = et al.
|publish_date = 16 November 2020
|description = Coronal heating models meet damped slow magnetoacoustic waves
|image=Icon394.png}}

{{Nugget Badge
|title = Self-Consistent Flare Model
|number = 393
|first_author = Wenzhi RUAN
|second_author = and Rony KEPPENS
|publish_date = 2 November 2020
|description = Energy transport by fast particles made self-consistent with MHD flare modeling
|image=Icon393.png}}

{{Nugget Badge
|title = Hot Flare Onsets
|number = 392
|first_author = Hugh HUDSON
|second_author = et al.
|publish_date = 26 October 2020
|description = The initial soft X-ray temperatures of solar flares tend to be in the 10-15 MK range
|image=Icon392.png}}

{{Nugget Badge
|title = Electric Current Neutralization and Eruption
|number = 391
|first_author = Ellis AVALLONE
|second_author = and Xudong SUN
|publish_date = 19 October 2020
|description = Coronal currents without neutralizing return currents appear to
|image=Icon391.png}}

{{Nugget Badge
|title = Prediction of Solar Cycle 25
|number = 390
|first_author = Leif SVALGAARD
|second_author =
|publish_date = 5 October 2020
|description = Now we know how big the next solar maximum will be
|image=Icon390.png}}

{{Nugget Badge
|title = Flare/CME Cartoon Archive
|number = 389
|first_author = Hugh HUDSON
|second_author =
|publish_date = 27 September 2020
|description = A new edition of the Flare/CME archive, nearly a half kilotoon now
|image=Icon389.png}}

{{Nugget Badge
|title = Submerged Flare Acoustic Sources
|number = 388
|first_author = Juan Camilo BUITRAGO CASAS
|second_author = and Angel MARTÍNEZ
|publish_date = 13 September 2020
|description = Flare acoustic radiation emanates from a source _inside_ the Sun
|image=Icon388.png}}

{{Nugget Badge
|title = Circular Ribbon Flare at Microwaves
|number = 387
|first_author = Jeongwoo LEE
|second_author =
|publish_date = 31 August 2020
|description = Breakout reconnection reveals itself via microwave polarization measurements.
|image=Icon387.png}}

{{Nugget Badge
|title = Relation of Non-neutralized electric currents and the activity in active regions
|number = 386
|first_author = P. VEMAREDDY
|second_author =
|publish_date = 24 August 2020
|description = Non-neutralized coronal current systems contribute to CME eruptions
|image=Icon386.png}}

{{Nugget Badge
|title = White-light emission and photospheric magnetic field changes in flares
|number = 385
|first_author = J. Sebastián CASTELLANOS DURÁN
|second_author = and Lucia KLEINT
|publish_date = 17 August 2020
|description = There are strong correlations between white-light flare emissions and line-of-sight magnetic field changes
|image=Icon385.png}}

{{Nugget Badge
|title = Sunspot Differential Rotation in an X-class Flare
|number = 384
|first_author = Richard GRIMES,
|second_author = Balázs PINTÉR and Huw MORGAN
|publish_date = 10 August 2020
|description = Observations suggesting how the coronal tail can wag the photospheric dog
|image=Icon384.png}}

{{Nugget Badge
|title = Energy Partitioning in a Nonthermally Dominated Two-loop Solar Flare
|number = 383
|first_author = Galina MOTORINA
|second_author = et al.
|publish_date = 3 August 2020
|description = Modeling the propagation of energy via GX Simulator in an early-impulsive flare
|image=Icon383.png}}

{{Nugget Badge
|title = SOL2013-11-10 Eruptive Circular-ribbon Flare with Extended Remote Brightenings
|number = 382
|first_author = Chang LIU
|second_author = et al.
|publish_date = 31 July 2020
|description = A circular-ribbon event can launch an eruption by breaking through its separatrix dome
|image=Icon382.png}}

{{Nugget Badge
|title = Extreme-Ultraviolet Late Phase of Solar Flares
|number = 381
|first_author = Rui LIU
|second_author =
|publish_date = 22 June 2020
|description = Both arcade and circular-ribbon flares may sometimes spawn EUV late phase emission
|image=Icon381.png}}

{{Nugget Badge
|title = Energy transport by accelerated particles in the quiet solar atmosphere
|number = 380
|first_author = Lars FROGNER,
|second_author = Boris GUDIKSEN and Helle BAKKE
|publish_date = 15 June 2020
|description = A first study of non-thermal particles integrated into an MHD simulation of the solar atmosphere
|image=Icon380.png}}

{{Nugget Badge
|title = Quasi-periodic pulsations as indicators of oscillatory processes in solar flares
|number = 379
|first_author = Elena KUPRIYANOVA
|second_author = et al.
|publish_date = 11 May 2020
|description = Many, many QPPs
|image=Icon379.png}}

{{Nugget Badge
|title = Rejuvenating Solar Flare Termination Shocks as Particle Accelerators
|number = 378
|first_author = Bin CHEN
|second_author =
|publish_date = 4 May 2020
|description = At last, clear evidence for a long-predicted phenomenon
|image=Icon378.png}}

{{Nugget Badge
|title = Broad symmetrical Doppler-shifted Fe XXI line profiles
|number = 377
|first_author = Vanessa POLITO
|second_author =
|publish_date = 20 April 2020
|description = It is difficult to explain "evaporation" line profiles by superposition of unresolved flows
|image=Icon377.png}}

{{Nugget Badge
|title = Phenomena in the unusually long pre-impulsive phase of SOL2011-06-07
|number = 376
|first_author = Marian KARLICKÝ,
|second_author = Jana KA&Scaron;PAROVÁ, and Robert SYCH
|publish_date = 13 April 2020
|description = A massive and slowly-rising filament eruption reveals important new signatures of the physics
|image=Icon376.png}}

{{Nugget Badge
|title = Evidence for a Coronal Shock Wave Origin for Relativistic Protons Producing Solar Gamma-Rays and Observed by Neutron Monitors at Earth‎
|number = 375
|first_author = Athanasios KOULOUMVAKOS
|second_author = and Gerry SHARE
|publish_date = 6 April 2020
|description = Successful modeling of prolonged solar gamma-ray emissions and terrestrial ground-level cosmic-ray events
|image=Icon375.png}}

{{Nugget Badge
|title = Using overlappogram data to find hot flare plasma
|number = 374
|first_author = Louise HARRA
|
|publish_date = 23 March 2020
|description = Imaging Fe XXIV at high resolution with the EIS slot data
|image=Icon374.png}}

{{Nugget Badge
|title = SOL2017-09-04 (M5.5) 2017 as a Source of Relativistic Electrons and Protons
|number = 373
|first_author = Alexei STRUMINSKII
| (see text)
|publish_date = 16 March 2020
|description = Flare-accelerated particles, rather than SEPs, energize sustained gamma-ray emission
|image=Icon373.png}}

{{Nugget Badge
|title = Heating of the solar photosphere during a white-light flare‎
|number = 372
|first_author = Jan JURČÁK
| (see text)
|publish_date = 2 March 2020
|description = The best-ever spectrum of the flare photosphere
|image=Icon372.png}}

{{Nugget Badge
|title = A Hot Cusp-Shaped Confined Solar Flare
|number = 371
|first_author = Aaron HERNANDEZ-PEREZ
|publish_date = 24 February 2020
|description = A flare may have a prominent hot cusp with the help of any eruption
|image=Icon371.png}}

{{Nugget Badge
|title = The Temporal and Spatial Extension of Gamma-ray Emission from the Sun
|number = 370
|first_author = Nat GOPALSWAMY
|publish_date = 17 February 2020
|description = Sustained solar γ-rays and solar cosmic rays
|image=Icon370.ng.png}}

{{Nugget Badge
|title = A PSP Perihelion
|number = 369
|first_author = Jessie DUNCAN
|second_author = and Hugh Hudson
|publish_date = 20 January 2020
|description = The Parker Solar Probe enters its fourth perihelion already. Now
|image=Icon369.png}}

{{Nugget Badge
|title = Remembering John Brown
|number = 368
|first_author = Alec MacKINNON
|second_author =
|publish_date = 13 January 2020
|description = John passed away unexpectedly on 16 November 2019
|image=Icon368.png}}

{{Nugget Badge
|title = A Global Survey of EUV Coronal Power Spectra
|number = 367
|first_author = Karl Battams
|second_author =
|publish_date = 30 December 2019
|description = Time-series parameter maps of imaged power spectra from an AIA pipeline
|image=Icon367.png}}

{{Nugget Badge
|title = Cosmic Rays over the Rainbow Bridge
|number = 366
|first_author = Hugh Hudson
|second_author = Alec MacKinnon
|publish_date = 16 December 2019
|description = Cosmic rays approach the Sun
|image=Icon366.png}}

{{Nugget Badge
|title = Spectropolarimetric Insight into Plasma-Sheet Dynamics of a Solar Flare
|number = 365
|first_author = Ryan French
|second_author =
|publish_date = 9 December 2019
|description = CoMP polarization patterns in SOL2017-09-10 are amazing
|image=Icon365.png}}

{{Nugget Badge
|title = Lorentz Force Evolution Reveals the Energy Build-up Processes during Recurrent Eruptive Solar Flares‎
|number = 364
|first_author = Ranadeep Sarkar,
|second_author = Nandita Srivastava and Astrid Veronig
|publish_date = 18 November 2019
|description = The net Lorentz force clearly exhibits a build-up and release pattern
|image=Icon364.png}}

{{Nugget Badge
|title = Flare waiting times depend on their magnitudes
|number = 363
|first_author = Hugh Hudson
|second_author =
|publish_date = 11 November 2019
|description = Surprising new evidence for the flare build-up and release process
|image=Icon363.png}}

{{Nugget Badge
|title = Can magnetic reconnection cause solar rainstorms?‎
|number = 362
|first_author = Petra Kohutova
|second_author =
|publish_date = 4 November 2019
|description = Impulsive coronal heating resulting from reconnection can trigger coronal rain
|image=Icon362.png}}

{{Nugget Badge
|title = Non-radial jets on the edges of active regions
|number = 361
|first_author = Peter Wyper
|second_author =
|publish_date = 14 October 2019
|description = The very common jet structures we see can naturally combine twist and breakout
|image=Icon361.png}}

{{Nugget Badge
|title = Searching SOLfully within the Nuggets
|number = 360
|first_author = Hugh Hudson
|second_author =
|publish_date = 7 October 2019
|description = The IAU target identifier works well for finding items about a particular event
|image=Icon360.png}}

{{Nugget Badge
|title = Submillimeter Radiation as the Thermal Component of the Neupert Effect
|number = 359
|first_author = Guillermo Giménez de Castro
|second_author =
|publish_date = 31 September 2019
|description = Flare radiation at the highest frequencies can be bremsstrahlung
|image=Icon359.png}}

{{Nugget Badge
|title = The "Last Best" Flares
|number = 358
|first_author = Hugh Hudson,
|second_author = Ed Cliver, and Brian Dennis
|publish_date = 24 September 2019
|description = Major flares tend to happen at the very ends of sunspot cycles
|image=Icon358.png}}

{{Nugget Badge
|title = Dynamic Processes of the Moreton Wave on 2014 March 29‎
|number = 357
|first_author = Denis Cabezas
|second_author = and the FMT team
|publish_date = 16 September 2019
|description = A beautiful Moreton wave excited by the best-observed flare ever
|image=Icon357.png}}

{{Nugget Badge
|title = EVE-RHESSI DEM Models and the Low-energy Cutoff for Nonthermal Electrons
|number = 356
|first_author = Jim McTiernan
|second_author =
|publish_date = 9 September 2019
|description = Characterizing flare temperature distributions helps to define the non-thermal energy release
|image=Icon356.png}}

{{Nugget Badge
|title = Stealth Coronal Mass Ejections from Active Regions
|number = 355
|first_author = Jennifer O'Kane
|second_author =
|publish_date = 26 August 2019
|description = Perhaps just feeble versions of the same magnetic disease...
|image=Icon355.png}}

{{Nugget Badge
|title = Do Kepler Superflare Stars Really Include Slowly Rotating Sun-like Stars?‎
|number = 354
|first_author = Yuta NOTSU
|second_author =
|publish_date = 15 July 2019
|description = Kepler superflares hint at solar superflares
|image=Icon354.png}}

{{Nugget Badge
|title = Localized Microwave and EUV Bright Structures in an Eruptive Prominence
|number = 353
|first_author = Jing HUANG
|second_author =
|publish_date = 22 June 2019
|description = Detailed correlations between EUV and microwaves in prominence fine structures
|image=Icon353.png}}

{{Nugget Badge
|title = Broken-up hard X-ray spectra found for a loop-top source during a solar limb flare
|number = 352
|first_author = Hao NING,
|second_author = Yao CHEN and Jeongwoo LEE
|publish_date = 16 June 2019
|description = SOL2017-09-10 coronal hard X-ray sources
|image=Icon352.png}}

{{Nugget Badge
|title = The Cosmic-Ray Shadow and Coronal Magnetism
|number = 351
|first_author = Frederik Tenholt
|second_author =
|publish_date = 27 May 2019
|description = The coronal magnetic field measured in Antarctica
|image=Icon351.png}}

{{Nugget Badge
|title = Kristian Birkeland
|number = 350
|first_author = Hugh HUDSON
|second_author = and Lyndsay FLETCHER
|publish_date = 6 May 2019
|description = Space weather a century ago: Kristian Birkeland
|image=Icon350.png}}

{{Nugget Badge
|title = Warm UV loops heated by small-scale cancellation events
|number = 349
|first_author = Seray ŞAHIN
|second_author = and Vasyl YURCHYSHYN
|publish_date = 22 April 2019
|description = Precisely locating the footpoints of warm coronal loops helps identify their source(s) of excitation
|image=Icon349.png}}

{{Nugget Badge
|title = Multiple Regions of Shock-accelerated Particles during a Solar Coronal Mass Ejection
|number = 348
|first_author = Diana MOROSAN
|second_author =
|publish_date = 1 April 2019
|description = LOFAR identifies herringbone sources within the flank of the SOL2017-09-10 shock - no joke
|image=Icon348.png}}

{{Nugget Badge
|title = Persistent Quasi-Periodic Pulsations Detected During the Large X8.2 Solar Flare
|number = 347
|first_author = Laura HAYES
|second_author = and Peter GALLAGHER
|publish_date = 25 March 2019
|description = The most beautiful flare has the most beautiful pulsations
|image=Icon347.png}}

{{Nugget Badge
|title = Is the coronal magnetic field braiding?
|number = 346
|first_author = Markus ASCHWANDEN
|second_author =
|publish_date = 11 March 2019
|description = This iconic cartoon does not relate well to the observations
|image=Icon346.png}}

{{Nugget Badge
|title = An energetic pre-flare: electron distributions in magnetic reconnection outflows
|number = 345
|first_author = Marina BATTAGLIA,
|second_author = Eduard KONTAR and Galina MOTORINA
|publish_date = 18 February 2019
|description = Assessing energy partition in a pre-impulsive flare development
|image=Icon345.png}}

{{Nugget Badge
|title = Linear Polarization in H-alpha Flares
|number = 344
|first_author = Tomoko KAWATE
|second_author = and Yoichiro HANAOKA
|publish_date = 4 February 2019
|description = H-alpha polarization is rarely observable but, in once case, very suggestive
|image=Icon344.png}}

{{Nugget Badge
|title = Short-Period Waves
|number = 343
|first_author = Sijie YU
|second_author = and Bin CHEN
|publish_date = 21 January 2019
|description = New decimetric imaging spectroscopy suggests Alfvénic energy transport in flares
|image=Icon343.png}}

{{Nugget Badge
|title = The Interesting RHESSI/SAS Archive
|number = 342
|first_author = Hugh HUDSON
|second_author = and Martin FIVIAN
|publish_date = 8 January 2019
|description = The full mission database shows RHESSI to have been very stable geometrically
|image=Icon342.png}}

{{Nugget Badge
|title = Homologous White Light Solar Flares‎
|number = 341
|first_author = Paolo ROMANO
|second_author = and Abouazza ELMHAMDI
|publish_date = 31 December 2018
|description = Homologous white-light flares, in rapid succession, and coronal null points
|image=Icon341.png}}

{{Nugget Badge
|title = The flight of FOXSI-3
|number = 340
|first_author = Lindsay GLESENER
|second_author = and Noriyuki NARUKAGE
|publish_date = 10 December 2018
|description = Single-photon counting and direct focusing across hard and soft energies
|image=Icon340.png}}

{{Nugget Badge
|title = Stellar Flares and Starspots
|number = 339
|first_author = Lauren DOYLE
|second_author =
|publish_date = 3 December 2018
|description = Stellar flares don't spatially match their starspots
|image=Icon339.png}}

{{Nugget Badge
|title = Neutron Production in Solar Flares
|number = 338
|first_author = Ron MURPHY
|second_author = and Gerry SHARE
|publish_date = 26 November 2018
|description = Neutron astronomy helps us understand solar flares
|image=Icon338.png}}

{{Nugget Badge
|title = Cycle 25 Strikes Again
|number = 337
|first_author = Kamil BICZ
|second_author =
|publish_date = 20 November 2018
|description = A second, larger Cycle 25 sunspot
|image=Icon337.png}}

{{Nugget Badge
|title = Remembering Marcos Machado via his research
|number = 336
|first_author = Hugh HUDSON
|second_author =
|publish_date = 13 November 2018
|description = Recalling a friend and colleague, and admiring his final paper
|image=Icon336.png}}

{{Nugget Badge
|title = CORONAS/SPIRIT Mg XII and Nanoflares‎
|number = 335
|first_author = Anton REVA
|second_author =
|publish_date = 22 October 2018
|description = Monochromatic Mg XII spectroheliography sets severe limits on nanoflare heating models
|image=Icon335.png}}

{{Nugget Badge
|title = White-light Emission and Non-thermal Electrons‎
|number = 334
|first_author = Kyoung-Sun LEE
|second_author =
|publish_date = 8 October 2018
|description = An intimate relationship between accelerated electrons and visible flare continuum
|image=Icon334.png}}

{{Nugget Badge
|title = Coronal Hard X-ray Sources Revisited
|number = 333
|first_author = Brian DENNIS
|second_author =
|publish_date = 24 September 2018
|description = Reporting some over-interpretation of the evidence for "coronal thick targets"
|image=Icon333.png}}

{{Nugget Badge
|title = Photospheric response to a flare
|number = 332
|first_author = Mike WHEATLAND
|second_author =
|publish_date = 17 September 2018
|description = Sudden changes in the magnetic field in the low atmosphere associated with particle acceleration
|image=Icon332.png}}

{{Nugget Badge
|title = New Views of Global Solar Magnetic Field Evolution Over Four Solar Cycles
|number = 331
|first_author = David WEBB
|second_author =
|publish_date = 27 August 2018
|description = A digital archive of Pat McIntosh's 44 years of solar synoptic observations
|image=Icon331.png}}

{{Nugget Badge
|title = Understanding the co-spatial return current in solar flares
|number = 330
|first_author = Meriem ALAOUI
|second_author = and Gordon HOLMAN
|publish_date = 6 August 2018
|description = Completing the circuit in a thick-target model
|image=Icon330.png}}

{{Nugget Badge
|title = 3D Magnetic Reconnection at a Coronal Null Point
|number = 329
|first_author = Shane MALONEY,
|second_author = Aidan O'Flannagain and Peter Gallagher
|publish_date = 30 July 2018
|description = Large-scale reconnection involved in Type I radio noise storm
|image=Icon329.png}}

{{Nugget Badge
|title = The true dawn of multimessenger astronomy
|number = 328
|first_author = Hugh Hudson
|second_author =
|publish_date = 23 July 2018
|description = Ever since the Carrington flare
|image=Icon328.png}}

{{Nugget Badge
|title = Microwave Imaging Spectroscopy of Flares is Here‎
|number = 327
|first_author = Dale E. Gary,
|second_author = EOVSA and RHESSI Teams
|publish_date = 16 July 2018
|description = Microwave imaging spectroscopy takes a giant leap forward with SOL2017-09-10
|image=Icon327.png}}

{{Nugget Badge
|title = Coronal nanoflares powered by footpoint reconnection
|number = 326
|first_author = Pradeep Chitta,
|second_author = Hardi Peter, and Sami Solanki
|publish_date = 9 July 2018
|description = Coronal nanoflares in active region cores can be powered by the magnetic reconnection in the lower solar atmosphere
|image=Icon326.png}}

{{Nugget Badge
|title = A remarkable, but confused, coronal hard X-ray source
|number = 325
|first_author = Alexandra Lysenko,
|second_author = Larisa Kashapova and Hugh Hudson
|publish_date = 25 June 2018
|description = A remarkable flare in 1999 adds to our short list of extended coronal hard X-ray/microwave sources
|image=Icon325.png}}

{{Nugget Badge
|title = Understanding HMI pseudocontinuum in white-light flares‎
|number = 324
|first_author = Michal &Scaron;vanda
|second_author = et al.
|publish_date = 28 May 2018
|description = The HMI pseudocontinuum (Ic) is ill-calibrated in regions with strong fields, i.e. for white-light flares
|image=Icon324.png}}

{{Nugget Badge
|title = To beam or not to beam - that is (still) the question
|number = 323
|first_author = Paulo Simões
|second_author = and Hugh Hudson
|publish_date = 14 May 2018
|description = Descriptions of the lower solar atmosphere of flares ca. Cycle 21 sound surprisingly current
|image=Icon323.png}}

{{Nugget Badge
|title = Observation of Cosmic Ray Spallation Events from SoHO‎
|number = 322
|first_author = Serge Koutchmy
|second_author = and Ehsan Tavabi
|publish_date = 7 May 2018
|description = LASCO's images capture high-energy nuclear interactions from cosmic-ray hits
|image=Icon322.png}}

{{Nugget Badge
|title = A Sunspot from Cycle 25 for sure
|number = 321
|first_author = Tomek Mrozek
|second_author = and Hugh Hudson
|publish_date = 10 April 2018
|description = YES! Cycle 25 is here!
|image=Icon321.png}}

{{Nugget Badge
|title = Blue-wing enhancement of the Mg II h and k lines in a flare
|number = 320
|first_author = Akiko TEI
|second_author =
|publish_date = 9 April 2018
|description = Flare loops involve a cool upflow preceding the hot evaporation flow
|image=Icon320.png}}

{{Nugget Badge
|title = NuSTAR detects X-ray flares in the quiet Sun
|number = 319
|first_author = Matej Kuhar
|second_author = and Säm Krucker
|publish_date = 26 March 2018
|description = Quiet-Sun flares may not be powerful, but they look a lot like ordinary flares
|image=Icon319.png}}

{{Nugget Badge
|title = Homologous CME/flares from AR 12371
|number = 318
|first_author = Panditi Vemareddy
|second_author = and Pascal Demoulín
|publish_date = 19 March 2018
|description = An excellent set of homologous flare/CMEs analyzed and explained
|image=Icon318.png}}

{{Nugget Badge
|title = Non-Maxwellian Diagnostics from SDO/EVE Spectra of an X-class Flare
|number = 317
|first_author = Elena Dzifčáková
|second_author = and Jaroslav Dudík
|publish_date = 16 February 2018
|description = Ratios of high-excitation ions can readily detect κ-distributions in flare plasmas
|image=Icon317.png}}

{{Nugget Badge
|title = Joint MinXSS and RHESSI Flare X-ray Spectra between 1 and 15 keV
|number = 316
|first_author = Chris Moore, Brian Dennis and the MinXSS Science Team
|publish_date = 5 February 2018
|description = MinXSS adds systematic views of flare soft X-ray spectra to RHESSI imagery
|image=Icon316.png}}

{{Nugget Badge
|title = Parameterized Flare Models with Chromospheric Compressions
|number = 315
|first_author = Adam Kowalski & Joel Allred
|publish_date = 17 January 2018
|description = A new approach to modeling the lower flare atmosphere
|image=FlareModelsKowalskiAllred.png}}

{{Nugget Badge
|title = A Curious Sunspot Group in 2018
|number = 314
|first_author = Hugh Hudson
|publish_date = 14 January 2018
|description = The first new sunspot group of 2018 emerged at the wrong latitude
|image = Icon314.png}}

{{Nugget Badge
|title = Tecumseh's Eclipse and Astrophysics
|number = 313
|first_author = Hugh Hudson
|publish_date = 25 December 2017
|description = The solar corona was first recognized as such, and named, in an eclipse of 1806
|image = Icon313.png}}

{{Nugget Badge
|title = Hunting for Hidden Tiny Flares
|number = 312
|first_author = Shin-nosuke ISHIKAWA
|publish_date = 27 November 2017
|description = FOXSI-2 says that episodic energy releases are still viable as a part of the coronal heating problem.
|image = Icon312.png}}

{{Nugget Badge
|title = Unusual Type III Burst Dynamics Produced by Diverging Magnetic Fields
|number = 311
|first_author = Patrick McCauley
|publish_date = 20 November 2017
|description = Unusual type III bursts follow coronal separatrix structures.
|image = Icon311.png}}

{{Nugget Badge
|title = Valderrama in the 21st Century
|number = 310
|first_author = Hugh Hudson
|publish_date = 31 October 2017
|description = A newly-described white-light flare from the 19th century!..
|image = Icon310.png}}

{{Nugget Badge
|title = Electron Scattering in the Flaring Corona
|number = 309
|first_author = Sophie Musset
|publish_date = 24 October 2017
|description = Diffusive transport may contribute to the trapping of electrons in coronal X-ray sources
|image = Icon309.png}}

{{Nugget Badge
|title = The Power of Turbulence
|number = 308
|first_author = Nic Bian
|publish_date = 25 September 2017
|description = Turbulent energy content may underlie flare energy transfer, magnetic reconnection, and particle acceleration
|image = Icon308.png}}

{{Nugget Badge
|title = The Kelvin Force and Loop-Top Concentration
|number = 307
|first_author = Kiyoto SHIBASAKI
|publish_date = 18 September 2017
|description = New physics can explain the perplexing overpressure at the flare looptop regions
|image = Icon307.png}}

{{Nugget Badge
|title = The Last Best Flare of Cycle 24?
|number = 306
|first_author = Säm Krucker
|second_author = and Hugh Hudson
|publish_date = 11 September 2017
|description = Right on schedule, Cycle 24 has produced a great flare (with a GLE)
|image = Icon306.png}}

{{Nugget Badge
|title = Electric Current Neutralization and Solar Eruption in Active Regions
|number = 305
|first_author = Yang LIU
|second_author =
|publish_date = 28 August 2017
|description = Active current systems in the solar corona don't have return currents
|image = Icon305.png}}

{{Nugget Badge
|title = RHESSI and the Megamovie
|number = 304
|first_author = Hugh Hudson, Laura Peticolas,
|second_author = and Juan Carlos Martínez Oliveros
|publish_date = 31 July 2017
|description = A wholly new way to view a solar eclipse, and to do solar astrometry
|image = Icon304.png}}

{{Nugget Badge
|title = Bastille Day 2017
|number = 303
|first_author = Hugh Hudson
|second_author = and Säm Krucker
|publish_date = 24 July 2017
|description = Interesting flares really do happen on Bastille Day...
|image = Icon303.png}}

{{Nugget Badge
|title = The Solar X-ray Limb III
|number = 302
|first_author = Marina Battaglia
|second_author = and Gordon Hurford
|publish_date = 12 June 2017
|description = RHESSI succeeds with a wholly new way to measure the solar diameter
|image = Icon302.png}}

{{Nugget Badge
|title = Double Coronal X-ray and Microwave Sources Associated With A Magnetic Breakout Solar Eruption
|number = 301
|first_author = Yao CHEN
|second_author =
|publish_date = 29 May 2017
|description = A different explanation of the double coronal hard X-ray sources
|image = Icon301.png}}

{{Nugget Badge
|title = A Lasso Model for Solar Gamma-ray Events
|number = 300
|first_author = Hugh Hudson
|second_author =
|publish_date = 15 May 2017
|description = A toy model hoping to explain the SEP/LAT relationship
|image = Icon300.png}}

[[RHESSI Science Nuggets 200 to 299|Next Nuggets]]

File:Icon527.png

2026-05-25T19:24:33Z

Hhudson:

Space Weather Impact of Three Solar Flares Observed at Millimeter Wavelengths

2026-05-25T19:03:21Z

Hhudson:

{{Infobox Nugget |name = Nugget
|title = Space Weather Impact of Three Solar Flares Observed at Millimeter Wavelengths
|number = 527
|first_author = Adriana VALIO et al.
|publish_date = May 25, 2026
|next_nugget = TBD
|previous_nugget = {{#ask: [[Category:Nugget]] [[RHESSI Nugget Index::526]]}}
}}

== Introduction ==

Solar flares are among the most energetic events in the solar system,
releasing vast amounts of energy across the electromagnetic spectrum
(from radio waves to gamma-rays) in a matter of minutes to hours.
Long-duration events are especially important because their prolonged
magnetic reconnection continuously accelerates particles, pumping
energy into the heliosphere long after the initial impulsive phase
has ended. Understanding the link between the properties of these
flares, the coronal mass ejections (CMEs) launched simultaneously,
and the disturbances caused at Earth is a central challenge of space
weather science.

One key area of observation of these phenomena -- millimeter radio waves -- has not been so well exploited.
The
[https://en.wikipedia.org/wiki/POlarization_Emission_of_Millimeter_Activity_at_the_Sun POEMAS]
telescope fills this key gap by making systematic solar observations at
45 and 90 Ghz (6.6 and 3.3 mm), crucial to understanding the
[https://en.wikipedia.org/wiki/Synchrotron_radiation gyrosynchrotron radiation]
fundamental to flare development.

We used this facility to carry out a detailed multiwavelength analysis (Ref. [1]) of
three long-duration solar flares during the solar maximum period of 2012
(Ref. [1]):
SOL2012-03-02 (M3.3; m4.80)
SOL2012-06-06 (M2.1; m3.12)
SOL2012-07-12 (X1.4; x1.85)
The adjusted ABCMX classes come from
[https://heliowiki.smce.nasa.gov/wiki/index.php/X-ray_Log_Letters] the previous Nugget]
as an experiment here; by either class scheme these events span a factor of 40
in magnitude.
The POEMAS high-frequency observations include measurements of circular
polarization, a key attribute not otherwise available.

== Radio Bursts and Gyrosynchrotron Modelling ==

Each flare was observed in both millimeter emission (POEMAS at 45
and 90 GHz) and microwaves
(the [https://en.wikipedia.org/wiki/STN Radio_Solar_Telescope_Network] at 1–15 GHz).
Combined radio spectra
spanning 5–90 GHz were assembled at four time intervals during each
burst and fitted with a gyrosynchrotron model using a Markov Chain
Monte Carlo (MCMC) algorithm. The fits yield four key physical
parameters: the magnetic field strength Bmag, the total number of
accelerated electrons Ne, the source size a, and the
spectral index of the electron energy distribution δ.

A main result is that all three events return remarkably similar
magnetic field strengths of about 160–180 G, despite the enormous
differences in overall flare energy.
This suggests a common coronal
magnetic configuration for these gyrosynchrotron-emitting sources,
and that what distinguishes powerful from weaker events is primarily
the number of electrons accelerated and the spatial extent of the
emitting region, not the field strength itself.
SOL2012-07-12 (X1.4; Figure 1)
had a source diameter roughly 3–6 times larger than the
other events and accelerated 6–13 times more electrons.
The spectral index δ was about 2.8 across all events,
harder than the typical microwave
range of 3–5.
This reflects a bias toward energetic events at millimeter
wavelengths, where only hard-spectrum flares produce detectable
flux at 90 GHz. In all three cases δ hardened further as each burst
progressed, reaching values near 2 by the end of the event.
The June and July flares also showed flux at 90 GHz exceeding that at
45 GHz, a "sub-THz component" previously reported by Ref. [2]
and indicating an additional emission mechanism at the
highest frequencies, distinct from the standard gyrosynchrotron
component.

[[File:527f1.png|center|thumb|700px|caption|Figure 1: 
Top row: Extreme ultraviolet (EUV) images captured by the Atmospheric
Imaging Assembly (AIA) instrument onboard the Solar Dynamics
Observatory (SDO) satellite, showing the SOL2012‐07‐12 flare at 171 Å
(left panel) and 304 Å (right panel). Bottom row: Light curves
of the SOL2012‐07‐12 flare. Left panel: Soft X‐ray emission observed
by GOES, with high‐energy (blue curve) and low‐energy (red curve)
channels. Right panel: Radio flux density light curves from 2 to
15 GHz recorded by RSTN, and at 45 and 90 GHz (red curve) observed
by POEMAS. The vertical red dashed line represents the approximate
launch time of the associated CME.
]]

== CMEs and Space Weather ==

Each of the three flares was accompanied by a coronal mass ejection
(CME) detected by LASCO/SOHO, and in all three cases the CME was
launched essentially simultaneously with the radio burst onset.
Two of the three events led to geomagnetic storms, as measured
by the
[https://wdc.kugi.kyoto-u.ac.jp/dstdir/ Dst index].
Notably the interaction of the July ICME with the magnetosphere also
triggered [https://en.wikipedia.org/wiki/Aurora aurora australis],
photographed by the crew of the International Space Station on 15 July 2012.

[[File:527f2.png|center|thumb|800px|caption|Figure 1: 
Scatter plots showing the positive correlation between the absolute
minimum Dst geomagnetic index (left) and CME velocity measured from
coronagraph observations (right) with the peak radio flux at 45 GH
Note that the March CME event missed Earth.
]]

== Conclusions ==

The central finding of this study is a consistent positive correlation
between the peak radio flux measured at 45 GHz and a suite of space
weather indicators: GOES flare class, SXR energy, CME velocity and
kinetic energy, ionospheric D-region depression, and geomagnetic
storm severity as quantified by Dst and Kp (Figure 2). The X1.4
event on 12 July 2012 sat at the high end of all these scales
simultaneously producing the brightest millimeter burst (116 SFU
at 45 GHz), the fastest and most energetic CME (884 km/s, 2.7 ×
1031 ergs), the deepest ionospheric depression (9 km), and the
strongest geomagnetic storm (Dst = −139 nT) of the three events.

The magnetic field strength in the gyrosynchrotron-emitting source
(~160–180 G) was essentially the same in all three flares, pointing
to a common magnetic topology. What differentiated the events was
the number of accelerated electrons and the source volume. Moreover,
the spectral index δ, consistently hard (~2.8, hardening toward 2
as each burst progressed), is characteristic of the millimeter-emitting
population and harder than what is typically inferred from
microwave-only studies, reflecting a selection effect at the highest
frequencies.

High-frequency millimeter radio observations thus appear to be a
promising tool for early space weather assessment: they are sensitive
to the most energetic particle populations, they respond on the
same timescale as the flare itself (allowing prediction hours or
even days before a CME arrives), and they correlate well with both
the CME properties and the ultimate geomagnetic impact. POEMAS
recorded 49 solar radio bursts during the 2012–2013 solar maximum,
at least half associated with halo or partial halo CMEs, offering
a valuable archive for extending this type of analysis to a larger
statistical sample.

== Acknowledgment ==

The authors of Ref. [1] and this Nugget are A. Valio, K.F. Lopez, J.L.
Gamonal Valenzuela, R.M. Romero Ramírez, and D.F. da Silva.

== References ==

[1] [https://doi.org/10.1029/2025JA03461 "Space weather impacts of three solar flares observed by the POEMAS
telescope at 45 and 90 GHz"]

[2] [http://adsabs.harvard.edu/abs/2004ApJ...603L.121K "A new solar burst spectral component emitting only in the terahertz range:]

[3] [ https://ui.adsabs.harvard.edu/abs/2013SoPh..283..651V "New circular polarization solar telescopes at two millimeter wavelength ranges"]

Space Weather Impact of Three Solar Flares Observed at Millimeter Wavelengths

2026-05-25T19:02:08Z

Hhudson:

{{Infobox Nugget |name = Nugget
|title = Space Weather Impact of Three Solar Flares Observed at Millimeter Wavelengths
|number = 527
|first_author = Adriana VALIO et al.
|publish_date = May 25, 2026
|next_nugget = TBD
|previous_nugget = {{#ask: [[Category:Nugget]] [[RHESSI Nugget Index::526]]}}
}}

== Introduction ==

Solar flares are among the most energetic events in the solar system,
releasing vast amounts of energy across the electromagnetic spectrum
(from radio waves to gamma-rays) in a matter of minutes to hours.
Long-duration events are especially important because their prolonged
magnetic reconnection continuously accelerates particles, pumping
energy into the heliosphere long after the initial impulsive phase
has ended. Understanding the link between the properties of these
flares, the coronal mass ejections (CMEs) launched simultaneously,
and the disturbances caused at Earth is a central challenge of space
weather science.

One key area of observation of these phenomena -- millimeter radio waves -- has not been so well exploited.
The
[https://en.wikipedia.org/wiki/POlarization_Emission_of_Millimeter_Activity_at_the_Sun POEMAS]
telescope fills this key gap by making systematic solar observations at
45 and 90 Ghz (6.6 and 3.3 mm), crucial to understanding the
[https://en.wikipedia.org/wiki/Synchrotron_radiation gyrosynchrotron radiation]
fundamental to flare development.

We used this facility to carry out a detailed multiwavelength analysis (Ref. [1]) of
three long-duration solar flares during the solar maximum period of 2012
(Ref. [1]):
SOL2012-03-02 (M3.3; m4.80)
SOL2012-06-06 (M2.1; m3.12)
SOL2012-07-12 (X1.4; x1.85)
The adjusted ABCMX classes come from
[https://heliowiki.smce.nasa.gov/wiki/index.php/X-ray_Log_Letters] the previous Nugget]
as an experiment here; by either class scheme these events span a factor of 40
in magnitude.
The POEMAS high-frequency observations include measurements of circular
polarization, a key attribute not otherwise available.

== Radio Bursts and Gyrosynchrotron Modelling ==

Each flare was observed in both millimeter emission (POEMAS at 45
and 90 GHz) and microwaves
(the [https://en.wikipedia.org/wiki/STN Radio_Solar_Telescope_Network] at 1–15 GHz).
Combined radio spectra
spanning 5–90 GHz were assembled at four time intervals during each
burst and fitted with a gyrosynchrotron model using a Markov Chain
Monte Carlo (MCMC) algorithm. The fits yield four key physical
parameters: the magnetic field strength Bmag, the total number of
accelerated electrons Ne, the source size a, and the
spectral index of the electron energy distribution δ.

A main result is that all three events return remarkably similar
magnetic field strengths of about 160–180 G, despite the enormous
differences in overall flare energy.
This suggests a common coronal
magnetic configuration for these gyrosynchrotron-emitting sources,
and that what distinguishes powerful from weaker events is primarily
the number of electrons accelerated and the spatial extent of the
emitting region, not the field strength itself.
SOL2012-07-12 (X1.4; Figure 1)
had a source diameter roughly 3–6 times larger than the
other events and accelerated 6–13 times more electrons.
The spectral index δ was about 2.8 across all events,
harder than the typical microwave
range of 3–5.
This reflects a bias toward energetic events at millimeter
wavelengths, where only hard-spectrum flares produce detectable
flux at 90 GHz. In all three cases δ hardened further as each burst
progressed, reaching values near 2 by the end of the event.
The June and July flares also showed flux at 90 GHz exceeding that at
45 GHz, a "sub-THz component" previously reported by Ref. [2]
and indicating an additional emission mechanism at the
highest frequencies, distinct from the standard gyrosynchrotron
component.

[[File:527f1.png|center|thumb|700px|caption|Figure 1: 
Top row: Extreme ultraviolet (EUV) images captured by the Atmospheric
Imaging Assembly (AIA) instrument onboard the Solar Dynamics
Observatory (SDO) satellite, showing the SOL2012‐07‐12 flare at 171 Å
(left panel) and 304 Å (right panel). Bottom row: Light curves
of the SOL2012‐07‐12 flare. Left panel: Soft X‐ray emission observed
by GOES, with high‐energy (blue curve) and low‐energy (red curve)
channels. Right panel: Radio flux density light curves from 2 to
15 GHz recorded by RSTN, and at 45 and 90 GHz (red curve) observed
by POEMAS. The vertical red dashed line represents the approximate
launch time of the associated CME.
]]

== CMEs and Space Weather ==

Each of the three flares was accompanied by a coronal mass ejection
(CME) detected by LASCO/SOHO, and in all three cases the CME was
launched essentially simultaneously with the radio burst onset.
Two of the three events led to geomagnetic storms, as measured
by the
[https://wdc.kugi.kyoto-u.ac.jp/dstdir/ Dst index].
Notably the interaction of the July ICME with the magnetosphere also
triggered [https://en.wikipedia.org/wiki/Aurora aurora australis],
photographed by the crew of the International Space Station on 15 July 2012.

[[File:527f2.png|center|thumb|800px|caption|Figure 1: 
Scatter plots showing the positive correlation between the absolute
minimum Dst geomagnetic index (left) and CME velocity measured from
coronagraph observations (right) with the peak radio flux at 45 GH
Note that the March CME event missed Earth.
]]

== Conclusions ==

The central finding of this study is a consistent positive correlation
between the peak radio flux measured at 45 GHz and a suite of space
weather indicators: GOES flare class, SXR energy, CME velocity and
kinetic energy, ionospheric D-region depression, and geomagnetic
storm severity as quantified by Dst and Kp (Figure 2). The X1.4
event on 12 July 2012 sat at the high end of all these scales
simultaneously producing the brightest millimeter burst (116 SFU
at 45 GHz), the fastest and most energetic CME (884 km/s, 2.7 ×
1031 ergs), the deepest ionospheric depression (9 km), and the
strongest geomagnetic storm (Dst = −139 nT) of the three events.

The magnetic field strength in the gyrosynchrotron-emitting source
(~160–180 G) was essentially the same in all three flares, pointing
to a common magnetic topology. What differentiated the events was
the number of accelerated electrons and the source volume. Moreover,
the spectral index δ, consistently hard (~2.8, hardening toward 2
as each burst progressed), is characteristic of the millimeter-emitting
population and harder than what is typically inferred from
microwave-only studies, reflecting a selection effect at the highest
frequencies.

High-frequency millimeter radio observations thus appear to be a
promising tool for early space weather assessment: they are sensitive
to the most energetic particle populations, they respond on the
same timescale as the flare itself (allowing prediction hours or
even days before a CME arrives), and they correlate well with both
the CME properties and the ultimate geomagnetic impact. POEMAS
recorded 49 solar radio bursts during the 2012–2013 solar maximum,
at least half associated with halo or partial halo CMEs, offering
a valuable archive for extending this type of analysis to a larger
statistical sample.

== Acknowledgment ==

The authors of Ref. [1] and this Nugget are A. Valio, K.F. Lopez, J.L.
Gamonal Valenzuela, R.M. Romero Ramírez, and D.F. da Silva.

== References ==

[1] [https://doi.org/10.1029/2025JA03461 "Space weather impacts of three solar flares observed by the POEMAS
telescope at 45 and 90 GHz"]

[2] [http://adsabs.harvard.edu/abs/2004ApJ...603L.121K "A new solar burst spectral component emitting only in the terahertz range:]

[3] [ https://ui.adsabs.harvard.edu/abs/2013SoPh..283..651V "New circular polarization soalr telescopes at two millimeter wavelength ranges"]

Space Weather Impact of Three Solar Flares Observed at Millimeter Wavelengths

2026-05-25T18:55:07Z

Hhudson:

{{Infobox Nugget |name = Nugget
|title = Space Weather Impact of Three Solar Flares Observed at Millimeter Wavelengths
|number = 527
|first_author = Adriana VALIO et al.
|publish_date = May 25, 2026
|next_nugget = TBD
|previous_nugget = {{#ask: [[Category:Nugget]] [[RHESSI Nugget Index::526]]}}
}}

== Introduction ==

Solar flares are among the most energetic events in the solar system,
releasing vast amounts of energy across the electromagnetic spectrum
(from radio waves to gamma-rays) in a matter of minutes to hours.
Long-duration events are especially important because their prolonged
magnetic reconnection continuously accelerates particles, pumping
energy into the heliosphere long after the initial impulsive phase
has ended. Understanding the link between the properties of these
flares, the coronal mass ejections (CMEs) launched simultaneously,
and the disturbances caused at Earth is a central challenge of space
weather science.

One key area of observation of these phenomena -- millimeter radio waves -- has not been so well exploited.
The
[https://en.wikipedia.org/wiki/POlarization_Emission_of_Millimeter_Activity_at_the_Sun POEMAS]
telescope fills this key gap by making systematic solar observations at
45 and 90 Ghz (6.6 and 3.3 mm), crucial to understanding the
[https://en.wikipedia.org/wiki/Synchrotron_radiation gyrosynchrotron radiation]
fundamental to flare development.

We used this facility to carry out a detailed multiwavelength analysis (Ref. [1]) of
three long-duration solar flares during the solar maximum period of 2012
(Ref. [1]):
SOL2012-03-02 (M3.3; m4.80)
SOL2012-06-06 (M2.1; m3.12)
SOL2012-07-12 (X1.4; x1.85)
The adjusted ABCMX classes come from
[https://heliowiki.smce.nasa.gov/wiki/index.php/X-ray_Log_Letters] the previous Nugget]
as an experiment here; by either class scheme these events span a factor of 40
in magnitude.
The POEMAS high-frequency observations include measurements of circular
polarization, a key attribute not otherwise available.

== Radio Bursts and Gyrosynchrotron Modelling ==

Each flare was observed in both millimeter emission (POEMAS at 45
and 90 GHz) and microwaves
(the [Rhttps://en.wikipedia.org/wiki/STN Radio_Solar_Telescope_Network] at 1–15 GHz).
Combined radio spectra
spanning 5–90 GHz were assembled at four time intervals during each
burst and fitted with a gyrosynchrotron model using a Markov Chain
Monte Carlo (MCMC) algorithm. The fits yield four key physical
parameters: the magnetic field strength Bmag, the total number of
accelerated electrons Ne, the source size a, and the
spectral index of the electron energy distribution δ.

A main result is that all three events return remarkably similar
magnetic field strengths of about 160–180 G, despite the enormous
differences in overall flare energy.
This suggests a common coronal
magnetic configuration for these gyrosynchrotron-emitting sources,
and that what distinguishes powerful from weaker events is primarily
the number of electrons accelerated and the spatial extent of the
emitting region, not the field strength itself.
SOL2012-07-12 (X1.4; Figure 1)
had a source diameter roughly 3–6 times larger than the
other events and accelerated 6–13 times more electrons.
The spectral index δ was about 2.8 across all events,
harder than the typical microwave
range of 3–5.
This reflects a bias toward energetic events at millimeter
wavelengths, where only hard-spectrum flares produce detectable
flux at 90 GHz. In all three cases δ hardened further as each burst
progressed, reaching values near 2 by the end of the event.
The June and July flares also showed flux at 90 GHz exceeding that at
45 GHz, a "sub-THz component" previously reported by Ref. [2]
and indicating an additional emission mechanism at the
highest frequencies, distinct from the standard gyrosynchrotron
component.

[[File:527f1.png|center|thumb|700px|caption|Figure 1: 
Top row: Extreme ultraviolet (EUV) images captured by the Atmospheric
Imaging Assembly (AIA) instrument onboard the Solar Dynamics
Observatory (SDO) satellite, showing the SOL2012‐07‐12 flare at 171 Å
(left panel) and 304 Å (right panel). Bottom row: Light curves
of the SOL2012‐07‐12 flare. Left panel: Soft X‐ray emission observed
by GOES, with high‐energy (blue curve) and low‐energy (red curve)
channels. Right panel: Radio flux density light curves from 2 to
15 GHz recorded by RSTN, and at 45 and 90 GHz (red curve) observed
by POEMAS. The vertical red dashed line represents the approximate
launch time of the associated CME.
]]

== CMEs and Space Weather ==

Each of the three flares was accompanied by a coronal mass ejection
(CME) detected by LASCO/SOHO, and in all three cases the CME was
launched essentially simultaneously with the radio burst onset.
Two of the three events led to geomagnetic storms, as measured
by the
[https://wdc.kugi.kyoto_u.ac.jp/dstdir Dst index].
Notably the interaction of the July ICME with the magnetosphere also
triggered [https://en.wikipedia.org/wiki/Aurora aurora australis],
photographed by the crew of the International Space Station on 15 July 2012.

[[File:527f2.png|center|thumb|800px|caption|Figure 1: 
Scatter plots showing the positive correlation between the absolute
minimum Dst geomagnetic index (left) and CME velocity measured from
coronagraph observations (right) with the peak radio flux at 45 GH
Note that the March CME event missed Earth.
]]

== Conclusions ==

The central finding of this study is a consistent positive correlation
between the peak radio flux measured at 45 GHz and a suite of space
weather indicators: GOES flare class, SXR energy, CME velocity and
kinetic energy, ionospheric D-region depression, and geomagnetic
storm severity as quantified by Dst and Kp (Figure 2). The X1.4
event on 12 July 2012 sat at the high end of all these scales
simultaneously producing the brightest millimeter burst (116 SFU
at 45 GHz), the fastest and most energetic CME (884 km/s, 2.7 ×
1031 ergs), the deepest ionospheric depression (9 km), and the
strongest geomagnetic storm (Dst = −139 nT) of the three events.

The magnetic field strength in the gyrosynchrotron-emitting source
(~160–180 G) was essentially the same in all three flares, pointing
to a common magnetic topology. What differentiated the events was
the number of accelerated electrons and the source volume. Moreover,
the spectral index δ, consistently hard (~2.8, hardening toward 2
as each burst progressed), is characteristic of the millimeter-emitting
population and harder than what is typically inferred from
microwave-only studies, reflecting a selection effect at the highest
frequencies.

High-frequency millimeter radio observations thus appear to be a
promising tool for early space weather assessment: they are sensitive
to the most energetic particle populations, they respond on the
same timescale as the flare itself (allowing prediction hours or
even days before a CME arrives), and they correlate well with both
the CME properties and the ultimate geomagnetic impact. POEMAS
recorded 49 solar radio bursts during the 2012–2013 solar maximum,
at least half associated with halo or partial halo CMEs, offering
a valuable archive for extending this type of analysis to a larger
statistical sample.

== Acknowledgment ==

The authors of Ref. [1] and this Nugget are A. Valio, K.F. Lopez, J.L.
Gamonal Valenzuela, R.M. Romero Ramírez, and D.F. da Silva.

== References ==

[1] [https://doi.org/10.1029/2025JA03461 "Space weather impacts of three solar flares observed by the POEMAS
telescope at 45 and 90 GHz"]

[2] [http://adsabs.harvard.edu/abs/2004ApJ...603L.121K "A new solar burst spectral component emitting only in the terahertz range:]

[3] [ https://ui.adsabs.harvard.edu/abs/2013SoPh..283..651V "New circular polarization soalr telescopes at two millimeter wavelength ranges"]

Space Weather Impact of Three Solar Flares Observed at Millimeter Wavelengths

2026-05-25T18:53:54Z

Hhudson:

{{Infobox Nugget |name = Nugget
|title = Space Weather Impact of Three Solar Flares Observed at Millimeter Wavelengths
|number = 527
|first_author = Adriana VALIO et al.
|publish_date = May 25, 2026
|next_nugget = TBD
|previous_nugget = {{#ask: [[Category:Nugget]] [[RHESSI Nugget Index::526]]}}
}}

== Introduction ==

Solar flares are among the most energetic events in the solar system,
releasing vast amounts of energy across the electromagnetic spectrum
(from radio waves to gamma-rays) in a matter of minutes to hours.
Long-duration events are especially important because their prolonged
magnetic reconnection continuously accelerates particles, pumping
energy into the heliosphere long after the initial impulsive phase
has ended. Understanding the link between the properties of these
flares, the coronal mass ejections (CMEs) launched simultaneously,
and the disturbances caused at Earth is a central challenge of space
weather science.

One key area of observation of these phenomena -- millimeter radio waves -- has not been so well exploited.
The
[https://en.wikipedia.org/wiki/POlarization_Emission_of_Millimeter_Activity_at_the_Sun POEMAS]
telescope fills this key gap by making systematic solar observations at
45 and 90 Ghz (6.6 and 3.3 mm), crucial to understanding the
[https://en.wikipedia.org/wiki/Synchrotron_radiation gyrosynchrotron radiation]
fundamental to flare development.

We used this facility to carry out a detailed multiwavelength analysis (Ref. [1]) of
three long-duration solar flares during the solar maximum period of 2012
(Ref. [1]):
SOL2012-03-02 (M3.3; m4.80)
SOL2012-06-06 (M2.1; m3.12)
SOL2012-07-12 (X1.4; x1.85)
The adjusted ABCMX classes come from
[https://heliowiki.smce.nasa.gov/wiki/index.php/X-ray_Log_Letters] the previous Nugget]
as an experiment here; by either class scheme these events span a factor of 40
in magnitude.
The POEMAS high-frequency observations include measurements of circular
polarization, a key attribute not otherwise available.

== Radio Bursts and Gyrosynchrotron Modelling ==

Each flare was observed in both millimeter emission (POEMAS at 45
and 90 GHz) and microwaves
(the [Rhttps://en.wikipedia.org/wiki/STN Radio_Solar_Telescope_Network] at 1–15 GHz).
Combined radio spectra
spanning 5–90 GHz were assembled at four time intervals during each
burst and fitted with a gyrosynchrotron model using a Markov Chain
Monte Carlo (MCMC) algorithm. The fits yield four key physical
parameters: the magnetic field strength Bmag, the total number of
accelerated electrons Ne, the source size a, and the
spectral index of the electron energy distribution δ.

A main result is that all three events return remarkably similar
magnetic field strengths of about 160–180 G, despite the enormous
differences in overall flare energy.
This suggests a common coronal
magnetic configuration for these gyrosynchrotron-emitting sources,
and that what distinguishes powerful from weaker events is primarily
the number of electrons accelerated and the spatial extent of the
emitting region, not the field strength itself.
SOL2012-07-12 (X1.4; Figure 1)
had a source diameter roughly 3–6 times larger than the
other events and accelerated 6–13 times more electrons.
The spectral index δ was about 2.8 across all events,
harder than the typical microwave
range of 3–5.
This reflects a bias toward energetic events at millimeter
wavelengths, where only hard-spectrum flares produce detectable
flux at 90 GHz. In all three cases δ hardened further as each burst
progressed, reaching values near 2 by the end of the event.
The June and July flares also showed flux at 90 GHz exceeding that at
45 GHz, a "sub-THz component" previously reported by Ref. [2]
and indicating an additional emission mechanism at the
highest frequencies, distinct from the standard gyrosynchrotron
component.

[[File:527f1.png|center|thumb|700px|caption|Figure 1: 
Top row: Extreme ultraviolet (EUV) images captured by the Atmospheric
Imaging Assembly (AIA) instrument onboard the Solar Dynamics
Observatory (SDO) satellite, showing the SOL2012‐07‐12 flare at 171 Å
(left panel) and 304 Å (right panel). Bottom row: Light curves
of the SOL2012‐07‐12 flare. Left panel: Soft X‐ray emission observed
by GOES, with high‐energy (blue curve) and low‐energy (red curve)
channels. Right panel: Radio flux density light curves from 2 to
15 GHz recorded by RSTN, and at 45 and 90 GHz (red curve) observed
by POEMAS. The vertical red dashed line represents the approximate
launch time of the associated CME.
]]

== CMEs and Space Weather ==

Each of the three flares was accompanied by a coronal mass ejection
(CME) detected by LASCO/SOHO, and in all three cases the CME was
launched essentially simultaneously with the radio burst onset.
Two of the three events led to geomagnetic storms, as measured
by the
[https://wdc.kugi.kyoto_u.ac.jp/dstdir Dst index].
Notably the interaction of the July ICME with the magnetosphere also
triggered [https://en.wikipedia.org/wiki/Aurora aurora australis],
photographed by the crew of the International Space Station on 15 July 2012.

[[File:527f2.png|center|thumb|700px|caption|Figure 1: 
Scatter plots showing the positive correlation between the absolute
minimum Dst geomagnetic index (left) and CME velocity measured from
coronagraph observations (right) with the peak radio flux at 45 GH
Note that the March CME event missed Earth.
]]

== Conclusions ==

The central finding of this study is a consistent positive correlation
between the peak radio flux measured at 45 GHz and a suite of space
weather indicators: GOES flare class, SXR energy, CME velocity and
kinetic energy, ionospheric D-region depression, and geomagnetic
storm severity as quantified by Dst and Kp (Figure 2). The X1.4
event on 12 July 2012 sat at the high end of all these scales
simultaneously producing the brightest millimeter burst (116 SFU
at 45 GHz), the fastest and most energetic CME (884 km/s, 2.7 ×
1031 ergs), the deepest ionospheric depression (9 km), and the
strongest geomagnetic storm (Dst = −139 nT) of the three events.

The magnetic field strength in the gyrosynchrotron-emitting source
(~160–180 G) was essentially the same in all three flares, pointing
to a common magnetic topology. What differentiated the events was
the number of accelerated electrons and the source volume. Moreover,
the spectral index δ, consistently hard (~2.8, hardening toward 2
as each burst progressed), is characteristic of the millimeter-emitting
population and harder than what is typically inferred from
microwave-only studies, reflecting a selection effect at the highest
frequencies.

High-frequency millimeter radio observations thus appear to be a
promising tool for early space weather assessment: they are sensitive
to the most energetic particle populations, they respond on the
same timescale as the flare itself (allowing prediction hours or
even days before a CME arrives), and they correlate well with both
the CME properties and the ultimate geomagnetic impact. POEMAS
recorded 49 solar radio bursts during the 2012–2013 solar maximum,
at least half associated with halo or partial halo CMEs, offering
a valuable archive for extending this type of analysis to a larger
statistical sample.

== Acknowledgment ==

The authors of Ref. [1] and this Nugget are A. Valio, K.F. Lopez, J.L.
Gamonal Valenzuela, R.M. Romero Ramírez, and D.F. da Silva.

== References ==

[1] [https://doi.org/10.1029/2025JA03461 "Space weather impacts of three solar flares observed by the POEMAS
telescope at 45 and 90 GHz"]

[2] [http://adsabs.harvard.edu/abs/2004ApJ...603L.121K "A new solar burst spectral component emitting only in the terahertz range:]

[3] [ https://ui.adsabs.harvard.edu/abs/2013SoPh..283..651V "New circular polarization soalr telescopes at two millimeter wavelength ranges"]

Space Weather Impact of Three Solar Flares Observed at Millimeter Wavelengths

2026-05-25T18:48:00Z

Hhudson: Initial upload No. 527

{{Infobox Nugget |name = Nugget
|title = Space Weather Impact of Three Solar Flares Observed at Millimeter Wavelengths
|number = 527
|first_author = Adriana VALIO et al.
|publish_date = May 25, 2026
|next_nugget = TBD
|previous_nugget = {{#ask: [[Category:Nugget]] [[RHESSI Nugget Index::526]]}}
}}

== Introduction ==

Solar flares are among the most energetic events in the solar system,
releasing vast amounts of energy across the electromagnetic spectrum
(from radio waves to gamma-rays) in a matter of minutes to hours.
Long-duration events are especially important because their prolonged
magnetic reconnection continuously accelerates particles, pumping
energy into the heliosphere long after the initial impulsive phase
has ended. Understanding the link between the properties of these
flares, the coronal mass ejections (CMEs) launched simultaneously,
and the disturbances caused at Earth is a central challenge of space
weather science.

One key area of observation of these phenomena -- millimeter radio waves -- has not been so well exploited.
The
[https://en.wikipedia.org/wiki/POlarization_Emission_of_Millimeter_Activity_at_the_Sun POEMAS]
telescope fills this key gap by making systematic solar observations at
45 and 90 Ghz (6.6 and 3.3 mm), crucial to understanding the
[https://en.wikipedia.org/wiki/Synchrotron_radiation gyrosynchrotron radiation]
fundamental to flare development.

We used this facility to carry out a detailed multiwavelength analysis (Ref. [1]) of
three long-duration solar flares during the solar maximum period of 2012
(Ref. [1]):
SOL2012-03-02 (M3.3; m4.80)
SOL2012-06-06 (M2.1; m3.12)
SOL2012-07-12 (X1.4; x1.85)
The adjusted ABCMX classes come from
[https://heliowiki.smce.nasa.gov/wiki/index.php/X-ray_Log_Letters] the previous Nugget]
as an experiment here; by either class scheme these events span a factor of 40
in magnitude.
The POEMAS high-frequency observations include measurements of circular
polarization, a key attribute not otherwise available.

== Radio Bursts and Gyrosynchrotron Modelling ==

Each flare was observed in both millimeter emission (POEMAS at 45
and 90 GHz) and microwaves
(the [Rhttps://en.wikipedia.org/wiki/STN Radio_Solar_Telescope_Network] at 1–15 GHz).
Combined radio spectra
spanning 5–90 GHz were assembled at four time intervals during each
burst and fitted with a gyrosynchrotron model using a Markov Chain
Monte Carlo (MCMC) algorithm. The fits yield four key physical
parameters: the magnetic field strength Bmag, the total number of
accelerated electrons Ne, the source size a, and the
spectral index of the electron energy distribution δ.

A main result is that all three events return remarkably similar
magnetic field strengths of about 160–180 G, despite the enormous
differences in overall flare energy.
This suggests a common coronal
magnetic configuration for these gyrosynchrotron-emitting sources,
and that what distinguishes powerful from weaker events is primarily
the number of electrons accelerated and the spatial extent of the
emitting region, not the field strength itself.
SOL2012-07-12 (X1.4; Figure 1)
had a source diameter roughly 3–6 times larger than the
other events and accelerated 6–13 times more electrons.
The spectral index δ was about 2.8 across all events,
harder than the typical microwave
range of 3–5.
This reflects a bias toward energetic events at millimeter
wavelengths, where only hard-spectrum flares produce detectable
flux at 90 GHz. In all three cases δ hardened further as each burst
progressed, reaching values near 2 by the end of the event.
The June and July flares also showed flux at 90 GHz exceeding that at
45 GHz, a "sub-THz component" previously reported by Ref. [2]
and indicating an additional emission mechanism at the
highest frequencies, distinct from the standard gyrosynchrotron
component.

[[File:527f1.png|center|thumb|600px|caption|Figure 1: 
Top row: Extreme ultraviolet (EUV) images captured by the Atmospheric
Imaging Assembly (AIA) instrument onboard the Solar Dynamics
Observatory (SDO) satellite, showing the SOL2012‐07‐12 flare at 171 Å
(left panel) and 304 Å (right panel). Bottom row: Light curves
of the SOL2012‐07‐12 flare. Left panel: Soft X‐ray emission observed
by GOES, with high‐energy (blue curve) and low‐energy (red curve)
channels. Right panel: Radio flux density light curves from 2 to
15 GHz recorded by RSTN, and at 45 and 90 GHz (red curve) observed
by POEMAS. The vertical red dashed line represents the approximate
launch time of the associated CME.
]]

== CMEs and Space Weather ==

Each of the three flares was accompanied by a coronal mass ejection
(CME) detected by LASCO/SOHO, and in all three cases the CME was
launched essentially simultaneously with the radio burst onset.
Two of the three events led to geomagnetic storms, as measured
by the
[https://wdc.kugi.kyoto_u.ac.jp/dstdir Dst index].
Notably the interaction of the July ICME with the magnetosphere also
triggered [https://en.wikipedia.org/wiki/Aurora aurora australis],
photographed by the crew of the International Space Station on 15 July 2012.

[[File:527f2.png|center|thumb|600px|caption|Figure 1: 
Scatter plots showing the positive correlation between the absolute
minimum Dst geomagnetic index (left) and CME velocity measured from
coronagraph observations (right) with the peak radio flux at 45 GH
Note that the March CME event missed Earth.
]]

== Conclusions ==

The central finding of this study is a consistent positive correlation
between the peak radio flux measured at 45 GHz and a suite of space
weather indicators: GOES flare class, SXR energy, CME velocity and
kinetic energy, ionospheric D-region depression, and geomagnetic
storm severity as quantified by Dst and Kp (Figure 2). The X1.4
event on 12 July 2012 sat at the high end of all these scales
simultaneously producing the brightest millimeter burst (116 SFU
at 45 GHz), the fastest and most energetic CME (884 km/s, 2.7 ×
1031 ergs), the deepest ionospheric depression (9 km), and the
strongest geomagnetic storm (Dst = −139 nT) of the three events.

The magnetic field strength in the gyrosynchrotron-emitting source
(~160–180 G) was essentially the same in all three flares, pointing
to a common magnetic topology. What differentiated the events was
the number of accelerated electrons and the source volume. Moreover,
the spectral index δ, consistently hard (~2.8, hardening toward 2
as each burst progressed), is characteristic of the millimeter-emitting
population and harder than what is typically inferred from
microwave-only studies, reflecting a selection effect at the highest
frequencies.

High-frequency millimeter radio observations thus appear to be a
promising tool for early space weather assessment: they are sensitive
to the most energetic particle populations, they respond on the
same timescale as the flare itself (allowing prediction hours or
even days before a CME arrives), and they correlate well with both
the CME properties and the ultimate geomagnetic impact. POEMAS
recorded 49 solar radio bursts during the 2012–2013 solar maximum,
at least half associated with halo or partial halo CMEs, offering
a valuable archive for extending this type of analysis to a larger
statistical sample.

== Acknowledgment ==

The authors of Ref. [1] and this Nugget are A. Valio, K.F. Lopez, J.L.
Gamonal Valenzuela, R.M. Romero Ramírez, and D.F. da Silva.

== References ==

[1] [https://doi.org/10.1029/2025JA03461 "Space weather impacts of three solar flares observed by the POEMAS
telescope at 45 and 90 GHz"]

[2] [http://adsabs.harvard.edu/abs/2004ApJ...603L.121K "A new solar burst spectral component emitting only in the terahertz range:]

[3] [ https://ui.adsabs.harvard.edu/abs/2013SoPh..283..651V "New circular polarization soalr telescopes at two millimeter wavelength ranges"]

File:527f2.png

2026-05-25T18:42:28Z

Hhudson:

File:527f1.png

2026-05-25T18:41:17Z

Hhudson:

X-ray Log Letters

2026-05-20T10:15:10Z

Hhudson: /* The greatest events (to the top) */

{{Infobox Nugget |name = Nugget
|title = X-ray Log Letters
|number = 526
|first_author = Hugh HUDSON and
|second_author = Ed CLIVER
|publish_date = May 18, 2026
|next_nugget = TBD
|previous_nugget = {{#ask: [[Category:Nugget]] [[RHESSI Nugget Index::525]]}}
}}

== Introduction ==

As all students of solar activity know, the
[https://www.stce.be/educational/classification naming scheme]
for solar flares involves the letters ABCMX.
These date from the dawn of the space age, when the first
[https://en.wikipedia.org/wiki/SOLRAD SOLRAD] satellites began to monitor
solar X-ray emission.
Flares of a wide range of brightnesses were immediately apparent, and
[https://www.noaa.gov NOAA]
ionospheric physicist Don Baker (Ref. [1]) came up with a classification
that matched decades of peak flux to letters: Cnn would mean nn x 10-4,
and the basic flux level 1.0 x 10-6 W/m2 would be class C1.0.
Initially it was just CMX ("Common", "Medium", "Extreme")
Each flare has a peak flux in the standard 1-8 Å band,
and the range of magnitudes of flare peak fluxes is so great that it's most
convenient to record the
[https://en.wikipedia.org/wiki/Common_logarithm logarithm] of the
flux.
This convention moved directly into the
[https://www.swpc.noaa.gov/products/goes-x-ray-flux GOES]
satellite era, and from 1974 the standardized flux measurements
have come from this series of spacecraft (Ref. [2]).

In standard units a C-class flare has a peak flux greater than 10-7
W/m2, with M-class and X-class greater by powers of 10.
Conventionally a flare 10% brighter than the threshold, with peak flux
1.1 x 10-7 W/m2, would then become a C1.1 flare.
The letter thus represents the truncated logarithm of the peak flux.
The magnitudes are not rounded off and represent the solar X-ray flux
conventionally in a 1-min integration interval.
A background quiescent solar emission level is not subtracted; these routine
observations show the total solar X-ray flux in "Sun-as-a-star" mode.
Weaker events near the background level, which can indeed exceed C1 during
active times, will thus not be quite as energetic as their name implies.

Low background solar X-ray fluxes during solar minima allowed the GOES
detector technology to detect fainter events, and so two new decades were
added to the letter string: A and B, with no particular descriptive
interpretation.
Thus we arrived at the current letter string ABCMX.

== The SphinX breakthrough (to the bottom) ==

The first routine flare monitoring with sufficient sensitivity to
detect the solar quiescent X-ray flux appeared with the SphinX
instrument from the
[https://scholar.google.com/citations?user=vDLMZPIAAAAJ&hl=pl Sylwester]
group at Wroc&lstrok;aw (Ref. [3]).
For 1-8 Å this turned out to be about two decades below the A level.
Hence, two more letters: Q "quiet" and S "small", leading to the more complete
string QSABCMX.
Figure 1 shows SphinX data from the 2009
[https://en.wikipedia.org/wiki/Solar_cycle solar minimum].

[[File:526f1.png|center|thumb|600px|caption|Figure 1: 
SphinX observations from solar minimum 2009, showing microflares down to the Q level
(as indicated by vertical blue lines at the bottom).
The regions marked with red show times of SphinX minimum counting rate, at levels far
below the original CMX range (Ref. [3]).
Green regions contain microflare excesses.
Excesses above this level are due to weak flares and quiescent active regions.
Translated to the GOES calibration, the weakest events are measured in units of
10-10 W/m2.
]]

== The greatest events (to the top) ==

At the top end of the GOES soft X-ray distribution, a handful of the most
extreme events had saturated the GOES 1-8 Å readout.
Ref. [4] describes an evenhanded patching of these items, together with a
correction for a systematic offset (Ref. [2]).
This produced a list of 37 >X10 events after background subtraction.
This basic manipulation departs from tradition, and so we provide this
[https://www.astro.gla.ac.uk/users/hsh3f/QSabcmxyz.txt greatest flares catalog]
(a ~2 MB .psf file) using the letter system "QSabcmxyz".
To translate, the new "y" class is the old "X10" class, sometimes now called
"S" (Ref. 5]), and the new catalog lists 37 of them.
The new "z" class has no examples yet (but we're hopeful), although the
[https://heliowiki.smce.nasa.gov/wiki/index.php/The_1859_Space_Weather_Event_Revisited Carrington event]
might have been in that category.

A sample of the newly lettered catalog is here, representing a signal-to-background requirement of 1 (flare
doubles the preflare level), resulting in a reduction of total number from 48,131 to 42,469 for the timespan
1974-2023.
The new letter string is QSabcmxyz, pleasingly symmetric.

Index ABCMX class QSabcmxyz
..
13190 SOL1989-03-05T23:56 C5.2 c4.65
13191 SOL1989-03-06T00:20 C5.1 c4.18
13192 SOL1989-03-06T00:39 C7.1 c7.55
13193 SOL1989-03-06T01:18 M3.0 m3.73
13194 SOL1989-03-06T03:23 M2.5 m3.37
13195 SOL1989-03-06T04:33 C4.6 c4.51
13196 SOL1989-03-06T11:42 C8.2 c9.89
13197 SOL1989-03-06T12:32 C4.9 c5.41
13198 SOL1989-03-06T14:10 X15. y1.90
13199 SOL1989-03-07T05:58 M2.0 m2.48
13200 SOL1989-03-07T11:14 C6.5 c5.79
13201 SOL1989-03-07T13:27 M4.1 m5.56
13202 SOL1989-03-07T13:44 M2.4 m5.57
13203 SOL1989-03-07T14:54 X1.8 x2.69
..
The catalog contains 37 y-class events (previously X10 or S), but no z-class examples because the Sun refuses to
cooperate. At the C (--> c) level, many events get downgraded because of background subtraction, but the systematic
historical scale adjustment described in Ref. [2] tends to compensate for that.

== Conclusions ==

See the [https://www.astro.gla.ac.uk/users/hsh3f/QSabcmxyz.html further discussion] of how QSabcmxyz works, or to access it directly click [https://www.astro.gla.ac.uk/users/hsh3f/QSabcmxyz.txt here] for a 2-MB text listing.

== References ==

[1] "Sentinels of the sun: forecasting space weather," B. Poppe and K. Jorden, 2006

[2] [https://www.sciencedirect.com/science/article/pii/B9780128143278000196 "GOES-R Series Solar X-ray and Ultraviolet Irradiance"]

[3] [https://doi.org/10.1007/s11207-019-1565-9 "Analysis of Quiescent Corona X-ray Spectra from SphinX During the 2009 Solar Minimum"]

[4] [https://ui.adsabs.harvard.edu/abs/2024SoPh..299...39H "The Greatest GOES Soft X-ray Flares"]

[5] [https://ui.adsabs.harvard.edu/abs/2025ApJ...979L..16T "The Occurrence of Powerful Flares Stronger than X10 Class in Solar Cycles"]

X-ray Log Letters

2026-05-20T10:14:20Z

Hhudson: /* The greatest events (to the top) */

{{Infobox Nugget |name = Nugget
|title = X-ray Log Letters
|number = 526
|first_author = Hugh HUDSON and
|second_author = Ed CLIVER
|publish_date = May 18, 2026
|next_nugget = TBD
|previous_nugget = {{#ask: [[Category:Nugget]] [[RHESSI Nugget Index::525]]}}
}}

== Introduction ==

As all students of solar activity know, the
[https://www.stce.be/educational/classification naming scheme]
for solar flares involves the letters ABCMX.
These date from the dawn of the space age, when the first
[https://en.wikipedia.org/wiki/SOLRAD SOLRAD] satellites began to monitor
solar X-ray emission.
Flares of a wide range of brightnesses were immediately apparent, and
[https://www.noaa.gov NOAA]
ionospheric physicist Don Baker (Ref. [1]) came up with a classification
that matched decades of peak flux to letters: Cnn would mean nn x 10-4,
and the basic flux level 1.0 x 10-6 W/m2 would be class C1.0.
Initially it was just CMX ("Common", "Medium", "Extreme")
Each flare has a peak flux in the standard 1-8 Å band,
and the range of magnitudes of flare peak fluxes is so great that it's most
convenient to record the
[https://en.wikipedia.org/wiki/Common_logarithm logarithm] of the
flux.
This convention moved directly into the
[https://www.swpc.noaa.gov/products/goes-x-ray-flux GOES]
satellite era, and from 1974 the standardized flux measurements
have come from this series of spacecraft (Ref. [2]).

In standard units a C-class flare has a peak flux greater than 10-7
W/m2, with M-class and X-class greater by powers of 10.
Conventionally a flare 10% brighter than the threshold, with peak flux
1.1 x 10-7 W/m2, would then become a C1.1 flare.
The letter thus represents the truncated logarithm of the peak flux.
The magnitudes are not rounded off and represent the solar X-ray flux
conventionally in a 1-min integration interval.
A background quiescent solar emission level is not subtracted; these routine
observations show the total solar X-ray flux in "Sun-as-a-star" mode.
Weaker events near the background level, which can indeed exceed C1 during
active times, will thus not be quite as energetic as their name implies.

Low background solar X-ray fluxes during solar minima allowed the GOES
detector technology to detect fainter events, and so two new decades were
added to the letter string: A and B, with no particular descriptive
interpretation.
Thus we arrived at the current letter string ABCMX.

== The SphinX breakthrough (to the bottom) ==

The first routine flare monitoring with sufficient sensitivity to
detect the solar quiescent X-ray flux appeared with the SphinX
instrument from the
[https://scholar.google.com/citations?user=vDLMZPIAAAAJ&hl=pl Sylwester]
group at Wroc&lstrok;aw (Ref. [3]).
For 1-8 Å this turned out to be about two decades below the A level.
Hence, two more letters: Q "quiet" and S "small", leading to the more complete
string QSABCMX.
Figure 1 shows SphinX data from the 2009
[https://en.wikipedia.org/wiki/Solar_cycle solar minimum].

[[File:526f1.png|center|thumb|600px|caption|Figure 1: 
SphinX observations from solar minimum 2009, showing microflares down to the Q level
(as indicated by vertical blue lines at the bottom).
The regions marked with red show times of SphinX minimum counting rate, at levels far
below the original CMX range (Ref. [3]).
Green regions contain microflare excesses.
Excesses above this level are due to weak flares and quiescent active regions.
Translated to the GOES calibration, the weakest events are measured in units of
10-10 W/m2.
]]

== The greatest events (to the top) ==

At the top end of the GOES soft X-ray distribution, a handful of the most
extreme events had saturated the GOES 1-8 Å readout.
Ref. [4] describes an evenhanded patching of these items, together with a
correction for a systematic offset (Ref. [2]).
This produced a list of 37 >X10 events after background subtraction.
This basic manipulation departs from tradition, and so we provide this
[https://www.astro.gla.ac.uk/users/hsh3f/QSabcmxyz.txt greatest flares catalog]
(a ~2 MB .psf file) using the letter system "QSabcmxyz".
To translate, the new "y" class is the old "X10" class, sometimes now called
"S" (Ref. 5]), and the new catalog lists 37 of them.
The new "z" class has no examples yet (but we're hopeful), although the
[https://heliowiki.smce.nasa.gov/wiki/index.php/The_1859_Space_Weather_Event_Revisited Carrington event]
might have been in that category.

A sample of the newly lettered catalog is here, representing a signal-to-background requirement of 1 (flare
doubles the preflare level), resulting in a reduction of total number from 48,131 to 42,469 for the timespan
1974-2023.
The new letter string is QSabcmxyz, pleasingly symmetric.

Index ABCMX class QSabcmxyz
..
13190 SOL1989-03-05T23:56 C5.2 c4.65
13191 SOL1989-03-06T00:20 C5.1 c4.18
13192 SOL1989-03-06T00:39 C7.1 c7.55
13193 SOL1989-03-06T01:18 M3.0 m3.73
13194 SOL1989-03-06T03:23 M2.5 m3.37
13195 SOL1989-03-06T04:33 C4.6 c4.51
13196 SOL1989-03-06T11:42 C8.2 c9.89
13197 SOL1989-03-06T12:32 C4.9 c5.41
13198 SOL1989-03-06T14:10 X15. y1.90
13199 SOL1989-03-07T05:58 M2.0 m2.48
13200 SOL1989-03-07T11:14 C6.5 c5.79
13201 SOL1989-03-07T13:27 M4.1 m5.56
13202 SOL1989-03-07T13:44 M2.4 m5.57
13203 SOL1989-03-07T14:54 X1.8 x2.69
..
The catalog contains 37 y-class events (previously X10 or S), but no z-class examples because the Sun refuses to
cooperate. At the C (->c) level, many events get downgraded because of background subtraction, but the systematic
historical scale adjustment described in Ref. [2] tends to compensate for that.

== Conclusions ==

See the [https://www.astro.gla.ac.uk/users/hsh3f/QSabcmxyz.html further discussion] of how QSabcmxyz works, or to access it directly click [https://www.astro.gla.ac.uk/users/hsh3f/QSabcmxyz.txt here] for a 2-MB text listing.

== References ==

[1] "Sentinels of the sun: forecasting space weather," B. Poppe and K. Jorden, 2006

[2] [https://www.sciencedirect.com/science/article/pii/B9780128143278000196 "GOES-R Series Solar X-ray and Ultraviolet Irradiance"]

[3] [https://doi.org/10.1007/s11207-019-1565-9 "Analysis of Quiescent Corona X-ray Spectra from SphinX During the 2009 Solar Minimum"]

[4] [https://ui.adsabs.harvard.edu/abs/2024SoPh..299...39H "The Greatest GOES Soft X-ray Flares"]

[5] [https://ui.adsabs.harvard.edu/abs/2025ApJ...979L..16T "The Occurrence of Powerful Flares Stronger than X10 Class in Solar Cycles"]

X-ray Log Letters

2026-05-20T06:53:24Z

Hhudson:

{{Infobox Nugget |name = Nugget
|title = X-ray Log Letters
|number = 526
|first_author = Hugh HUDSON and
|second_author = Ed CLIVER
|publish_date = May 18, 2026
|next_nugget = TBD
|previous_nugget = {{#ask: [[Category:Nugget]] [[RHESSI Nugget Index::525]]}}
}}

== Introduction ==

As all students of solar activity know, the
[https://www.stce.be/educational/classification naming scheme]
for solar flares involves the letters ABCMX.
These date from the dawn of the space age, when the first
[https://en.wikipedia.org/wiki/SOLRAD SOLRAD] satellites began to monitor
solar X-ray emission.
Flares of a wide range of brightnesses were immediately apparent, and
[https://www.noaa.gov NOAA]
ionospheric physicist Don Baker (Ref. [1]) came up with a classification
that matched decades of peak flux to letters: Cnn would mean nn x 10-4,
and the basic flux level 1.0 x 10-6 W/m2 would be class C1.0.
Initially it was just CMX ("Common", "Medium", "Extreme")
Each flare has a peak flux in the standard 1-8 Å band,
and the range of magnitudes of flare peak fluxes is so great that it's most
convenient to record the
[https://en.wikipedia.org/wiki/Common_logarithm logarithm] of the
flux.
This convention moved directly into the
[https://www.swpc.noaa.gov/products/goes-x-ray-flux GOES]
satellite era, and from 1974 the standardized flux measurements
have come from this series of spacecraft (Ref. [2]).

In standard units a C-class flare has a peak flux greater than 10-7
W/m2, with M-class and X-class greater by powers of 10.
Conventionally a flare 10% brighter than the threshold, with peak flux
1.1 x 10-7 W/m2, would then become a C1.1 flare.
The letter thus represents the truncated logarithm of the peak flux.
The magnitudes are not rounded off and represent the solar X-ray flux
conventionally in a 1-min integration interval.
A background quiescent solar emission level is not subtracted; these routine
observations show the total solar X-ray flux in "Sun-as-a-star" mode.
Weaker events near the background level, which can indeed exceed C1 during
active times, will thus not be quite as energetic as their name implies.

Low background solar X-ray fluxes during solar minima allowed the GOES
detector technology to detect fainter events, and so two new decades were
added to the letter string: A and B, with no particular descriptive
interpretation.
Thus we arrived at the current letter string ABCMX.

== The SphinX breakthrough (to the bottom) ==

The first routine flare monitoring with sufficient sensitivity to
detect the solar quiescent X-ray flux appeared with the SphinX
instrument from the
[https://scholar.google.com/citations?user=vDLMZPIAAAAJ&hl=pl Sylwester]
group at Wroc&lstrok;aw (Ref. [3]).
For 1-8 Å this turned out to be about two decades below the A level.
Hence, two more letters: Q "quiet" and S "small", leading to the more complete
string QSABCMX.
Figure 1 shows SphinX data from the 2009
[https://en.wikipedia.org/wiki/Solar_cycle solar minimum].

[[File:526f1.png|center|thumb|600px|caption|Figure 1: 
SphinX observations from solar minimum 2009, showing microflares down to the Q level
(as indicated by vertical blue lines at the bottom).
The regions marked with red show times of SphinX minimum counting rate, at levels far
below the original CMX range (Ref. [3]).
Green regions contain microflare excesses.
Excesses above this level are due to weak flares and quiescent active regions.
Translated to the GOES calibration, the weakest events are measured in units of
10-10 W/m2.
]]

== The greatest events (to the top) ==

At the top end of the GOES soft X-ray distribution, a handful of the most
extreme events had saturated the GOES 1-8 Å readout.
Ref. [4] describes an evenhanded patching of these items, together with a
correction for a systematic offset (Ref. [2]).
This produced a list of 37 >X10 events after background subtraction.
This basic manipulation departs from tradition, and so we provide this
[https://www.astro.gla.ac.uk/users/hsh3f/QSabcmxyz.txt greatest flares catalog]
(a ~2 MB .psf file) using the letter system "QSabcmxyz".
To translate, the new "y" class is the old "X10" class, sometimes now called
"S" (Ref. 5]), and the new catalog lists 37 of them.
The new "z" class has no examples yet (but we're hopeful), although the
[https://heliowiki.smce.nasa.gov/wiki/index.php/The_1859_Space_Weather_Event_Revisited Carrington event]
might have been in that category.

A sample of the newly lettered catalog is here, representing a signal-to-background requirement of 1 (flare
doubles the preflare level), resulting in a reduction of total number from 48,131 to 42,469 for the timespan
1974-2023.
The new letter string is QSabcmxyz, pleasingly symmetric.

Index ABCMX class QSabcmxyz
..
13190 SOL1989-03-05T23:56 C5.2 c4.65
13191 SOL1989-03-06T00:20 C5.1 c4.18
13192 SOL1989-03-06T00:39 C7.1 c7.55
13193 SOL1989-03-06T01:18 M3.0 m3.73
13194 SOL1989-03-06T03:23 M2.5 m3.37
13195 SOL1989-03-06T04:33 C4.6 c4.51
13196 SOL1989-03-06T11:42 C8.2 c9.89
13197 SOL1989-03-06T12:32 C4.9 c5.41
13198 SOL1989-03-06T14:10 X15. y1.90
13199 SOL1989-03-07T05:58 M2.0 m2.48
13200 SOL1989-03-07T11:14 C6.5 c5.79
13201 SOL1989-03-07T13:27 M4.1 m5.56
13202 SOL1989-03-07T13:44 M2.4 m5.57
13203 SOL1989-03-07T14:54 X1.8 x2.69
..
The catalog contains 37 y-class events (previously X10 or S), but no z-class examples because the Sun refuses to
cooperate. At the C->c level, many events get downgraded because of background subtraction, but the systematic
historical scale adjustment described in Ref. [2] tends to compensate for that.

== Conclusions ==

See the [https://www.astro.gla.ac.uk/users/hsh3f/QSabcmxyz.html further discussion] of how QSabcmxyz works, or to access it directly click [https://www.astro.gla.ac.uk/users/hsh3f/QSabcmxyz.txt here] for a 2-MB text listing.

== References ==

[1] "Sentinels of the sun: forecasting space weather," B. Poppe and K. Jorden, 2006

[2] [https://www.sciencedirect.com/science/article/pii/B9780128143278000196 "GOES-R Series Solar X-ray and Ultraviolet Irradiance"]

[3] [https://doi.org/10.1007/s11207-019-1565-9 "Analysis of Quiescent Corona X-ray Spectra from SphinX During the 2009 Solar Minimum"]

[4] [https://ui.adsabs.harvard.edu/abs/2024SoPh..299...39H "The Greatest GOES Soft X-ray Flares"]

[5] [https://ui.adsabs.harvard.edu/abs/2025ApJ...979L..16T "The Occurrence of Powerful Flares Stronger than X10 Class in Solar Cycles"]

X-ray Log Letters

2026-05-20T06:50:13Z

Hhudson: /* The greatest events (to the top) */

{{Infobox Nugget |name = Nugget
|title = X-ray Log Letters
|number = 526
|first_author = Hugh HUDSON and
|second_author = Ed CLIVER
|publish_date = May 18, 2026
|next_nugget = TBD
|previous_nugget = {{#ask: [[Category:Nugget]] [[RHESSI Nugget Index::525]]}}
}}

== Introduction ==

As all students of solar activity know, the
[https://www.stce.be/educational/classification naming scheme]
for solar flares involves the letters ABCMX.
These date from the dawn of the space age, when the first
[https://en.wikipedia.org/wiki/SOLRAD SOLRAD] satellites began to monitor
solar X-ray emission.
Flares of a wide range of brightnesses were immediately apparent, and
[https://www.noaa.gov NOAA]
ionospheric physicist Don Baker (Ref. [1]) came up with a classification
that matched decades of peak flux to letters: Cnn would mean nn x 10-4,
and the basic flux level 1.0 x 10-6 W/m2 would be class C1.0.
Initially it was just CMX ("Common", "Medium", "Extreme")
Each flare has a peak flux in the standard 1-8 Å band,
and the range of magnitudes of flare peak fluxes is so great that it's most
convenient to record the
[https://en.wikipedia.org/wiki/Common_logarithm logarithm] of the
flux.
This convention moved directly into the
[https://www.swpc.noaa.gov/products/goes-x-ray-flux GOES]
satellite era, and from 1974 the standardized flux measurements
have come from this series of spacecraft (Ref. [2]).

In standard units a C-class flare has a peak flux greater than 10-7
W/m2, with M-class and X-class greater by powers of 10.
Conventionally a flare 10% brighter than the threshold, with peak flux
1.1 x 10-7 W/m2, would then become a C1.1 flare.
The letter thus represents the truncated logarithm of the peak flux.
The magnitudes are not rounded off and represent the solar X-ray flux
conventionally in a 1-min integration interval.
A background quiescent solar emission level is not subtracted; these routine
observations show the total solar X-ray flux in "Sun-as-a-star" mode.
Weaker events near the background level, which can indeed exceed C1 during
active times, will thus not be quite as energetic as their name implies.

Low background solar X-ray fluxes during solar minima allowed the GOES
detector technology to detect fainter events, and so two new decades were
added to the letter string: A and B, with no particular descriptive
interpretation.
Thus we arrived at the current letter string ABCMX.

== The SphinX breakthrough (to the bottom) ==

The first routine flare monitoring with sufficient sensitivity to
detect the solar quiescent X-ray flux appeared with the SphinX
instrument from the
[https://scholar.google.com/citations?user=vDLMZPIAAAAJ&hl=pl Sylwester]
group at Wroc&lstrok;aw (Ref. [3]).
For 1-8 Å this turned out to be about two decades below the A level.
Hence, two more letters: Q "quiet" and S "small", leading to the more complete
string QSABCMX.
Figure 1 shows SphinX data from the 2009
[https://en.wikipedia.org/wiki/Solar_cycle solar minimum].

[[File:526f1.png|center|thumb|600px|caption|Figure 1: 
SphinX observations from solar minimum 2009, showing microflares down to the Q level
(as indicated by vertical blue lines at the bottom).
The regions marked with red show times of SphinX minimum counting rate, at levels far
below the original CMX range (Ref. [3]).
Green regions contain microflare excesses.
Excesses above this level are due to weak flares and quiescent active regions.
Translated to the GOES calibration, the weakest events are measured in units of
10-10 W/m2.
]]

== The greatest events (to the top) ==

At the top end of the GOES soft X-ray distribution, a handful of the most
extreme events had saturated the GOES 1-8 Å readout.
Ref. [4] describes an evenhanded patching of these items, together with a
correction for a systematic offset (Ref. [2]).
This produced a list of 37 >X10 events after background subtraction.
This basic manipulation departs from tradition, and so we provide this
[greatest flares]
catalog using the letter system "QSabcmxyz".
To translate, the new "y" class is the old "X10" class, sometimes now called
"S" (Ref. 5]), and the new catalog lists 37 of them.
The new "z" class has no examples yet (but we're hopeful), although the
[https://heliowiki.smce.nasa.gov/wiki/index.php/The_1859_Space_Weather_Event_Revisited Carrington event]
might have been in that category.

A sample of the newly lettered catalog is here, representing a signal-to-background requirement of 1 (flare
doubles the preflare level), resulting in a reduction of total number from 48,131 to 42,469 for the timespan
1974-2023.
The new letter string is QSabcmxyz, pleasingly symmetric.

Index ABCMX class QSabcmxyz
..
13190 SOL1989-03-05T23:56 C5.2 c4.65
13191 SOL1989-03-06T00:20 C5.1 c4.18
13192 SOL1989-03-06T00:39 C7.1 c7.55
13193 SOL1989-03-06T01:18 M3.0 m3.73
13194 SOL1989-03-06T03:23 M2.5 m3.37
13195 SOL1989-03-06T04:33 C4.6 c4.51
13196 SOL1989-03-06T11:42 C8.2 c9.89
13197 SOL1989-03-06T12:32 C4.9 c5.41
13198 SOL1989-03-06T14:10 X15. y1.90
13199 SOL1989-03-07T05:58 M2.0 m2.48
13200 SOL1989-03-07T11:14 C6.5 c5.79
13201 SOL1989-03-07T13:27 M4.1 m5.56
13202 SOL1989-03-07T13:44 M2.4 m5.57
13203 SOL1989-03-07T14:54 X1.8 x2.69
..
The catalog contains 37 y-class events (previously X10 or S), but no z-class examples because the Sun refuses to
cooperate. At the C->c level, many events get downgraded because of background subtraction, but the systematic
historical scale adjustment described in Ref. [2] tends to compensate for that.

== Conclusions ==

See the [https://www.astro.gla.ac.uk/users/hsh3f/QSabcmxyz.html further discussion] of how QSabcmxyz works, or to access it directly click [https://www.astro.gla.ac.uk/users/hsh3f/QSabcmxyz.txt here] for a 2-MB text listing.

== References ==

[1] "Sentinels of the sun: forecasting space weather," B. Poppe and K. Jorden, 2006

[2] [https://www.sciencedirect.com/science/article/pii/B9780128143278000196 "GOES-R Series Solar X-ray and Ultraviolet Irradiance"]

[3] [https://doi.org/10.1007/s11207-019-1565-9 "Analysis of Quiescent Corona X-ray Spectra from SphinX During the 2009 Solar Minimum"]

[4] [https://ui.adsabs.harvard.edu/abs/2024SoPh..299...39H "The Greatest GOES Soft X-ray Flares"]

[5] [https://ui.adsabs.harvard.edu/abs/2025ApJ...979L..16T "The Occurrence of Powerful Flares Stronger than X10 Class in Solar Cycles"]

X-ray Log Letters

2026-05-20T06:47:21Z

Hhudson: /* The greatest events (to the top) */

{{Infobox Nugget |name = Nugget
|title = X-ray Log Letters
|number = 526
|first_author = Hugh HUDSON and
|second_author = Ed CLIVER
|publish_date = May 18, 2026
|next_nugget = TBD
|previous_nugget = {{#ask: [[Category:Nugget]] [[RHESSI Nugget Index::525]]}}
}}

== Introduction ==

As all students of solar activity know, the
[https://www.stce.be/educational/classification naming scheme]
for solar flares involves the letters ABCMX.
These date from the dawn of the space age, when the first
[https://en.wikipedia.org/wiki/SOLRAD SOLRAD] satellites began to monitor
solar X-ray emission.
Flares of a wide range of brightnesses were immediately apparent, and
[https://www.noaa.gov NOAA]
ionospheric physicist Don Baker (Ref. [1]) came up with a classification
that matched decades of peak flux to letters: Cnn would mean nn x 10-4,
and the basic flux level 1.0 x 10-6 W/m2 would be class C1.0.
Initially it was just CMX ("Common", "Medium", "Extreme")
Each flare has a peak flux in the standard 1-8 Å band,
and the range of magnitudes of flare peak fluxes is so great that it's most
convenient to record the
[https://en.wikipedia.org/wiki/Common_logarithm logarithm] of the
flux.
This convention moved directly into the
[https://www.swpc.noaa.gov/products/goes-x-ray-flux GOES]
satellite era, and from 1974 the standardized flux measurements
have come from this series of spacecraft (Ref. [2]).

In standard units a C-class flare has a peak flux greater than 10-7
W/m2, with M-class and X-class greater by powers of 10.
Conventionally a flare 10% brighter than the threshold, with peak flux
1.1 x 10-7 W/m2, would then become a C1.1 flare.
The letter thus represents the truncated logarithm of the peak flux.
The magnitudes are not rounded off and represent the solar X-ray flux
conventionally in a 1-min integration interval.
A background quiescent solar emission level is not subtracted; these routine
observations show the total solar X-ray flux in "Sun-as-a-star" mode.
Weaker events near the background level, which can indeed exceed C1 during
active times, will thus not be quite as energetic as their name implies.

Low background solar X-ray fluxes during solar minima allowed the GOES
detector technology to detect fainter events, and so two new decades were
added to the letter string: A and B, with no particular descriptive
interpretation.
Thus we arrived at the current letter string ABCMX.

== The SphinX breakthrough (to the bottom) ==

The first routine flare monitoring with sufficient sensitivity to
detect the solar quiescent X-ray flux appeared with the SphinX
instrument from the
[https://scholar.google.com/citations?user=vDLMZPIAAAAJ&hl=pl Sylwester]
group at Wroc&lstrok;aw (Ref. [3]).
For 1-8 Å this turned out to be about two decades below the A level.
Hence, two more letters: Q "quiet" and S "small", leading to the more complete
string QSABCMX.
Figure 1 shows SphinX data from the 2009
[https://en.wikipedia.org/wiki/Solar_cycle solar minimum].

[[File:526f1.png|center|thumb|600px|caption|Figure 1: 
SphinX observations from solar minimum 2009, showing microflares down to the Q level
(as indicated by vertical blue lines at the bottom).
The regions marked with red show times of SphinX minimum counting rate, at levels far
below the original CMX range (Ref. [3]).
Green regions contain microflare excesses.
Excesses above this level are due to weak flares and quiescent active regions.
Translated to the GOES calibration, the weakest events are measured in units of
10-10 W/m2.
]]

== The greatest events (to the top) ==

At the top end of the GOES soft X-ray distribution, a handful of the most
extreme events had saturated the GOES 1-8 Å readout.
Ref. [4] describes an evenhanded patching of these items, together with a
correction for a systematic offset (Ref. [2]).
This produced a list of 37 >X10 events after background subtraction.
This basic manipulation departs from tradition, and so we provide this
[greatest flares]
catalog using the letter system "QSabcmxyz".
To translate, the new "y" class is the old "X10" class, sometimes now called
"S" (Ref. 5]), and the new catalog lists 37 of them.
The new "z" class has no examples yet (but we're hopeful), although the
[https://heliowiki.smce.nasa.gov/wiki/index.php/The_1859_Space_Weather_Event_Revisited Carrington event]
might have been in that category.

A sample of the newly lettered catalog is here, representing a signal-to-background requirement of 1 (flare
doubles the preflare level), resulting in a reduction of total number from 48,131 to 42,469 for the timespan
1974-2023.
The new letter string is QSabcmxyz, pleasingly symmetric.

Index ABCMX class QSabcmxyz
..
SOL1984-02-10T22:47 C9.1 m1.21
SOL1984-02-11T01:31 C3.7 c3.78
SOL1984-02-11T02:45 M2.9 m4.07
SOL1984-02-11T03:44 C2.0 c1.93
SOL1984-02-11T04:33 C2.1 c1.78
SOL1984-02-11T04:56 C2.1 c2.23
SOL1984-02-11T09:06 C2.6 c2.46
SOL1984-02-11T10:09 C1.8 c1.43
SOL1984-02-11T12:16 C3.0 c3.19
SOL1984-02-11T14:24 C4.8 c6.03
..
The catalog contains 37 y-class events (previously X10 or S), but no z-class examples because the Sun refuses to
cooperate. At the C->c level, many events get downgraded because of background subtraction, but the systematic
historical scale adjustment described in Ref. [2] tends to compensate for that.

== Conclusions ==

See the [https://www.astro.gla.ac.uk/users/hsh3f/QSabcmxyz.html further discussion] of how QSabcmxyz works, or to access it directly click [https://www.astro.gla.ac.uk/users/hsh3f/QSabcmxyz.txt here] for a 2-MB text listing.

== References ==

[1] "Sentinels of the sun: forecasting space weather," B. Poppe and K. Jorden, 2006

[2] [https://www.sciencedirect.com/science/article/pii/B9780128143278000196 "GOES-R Series Solar X-ray and Ultraviolet Irradiance"]

[3] [https://doi.org/10.1007/s11207-019-1565-9 "Analysis of Quiescent Corona X-ray Spectra from SphinX During the 2009 Solar Minimum"]

[4] [https://ui.adsabs.harvard.edu/abs/2024SoPh..299...39H "The Greatest GOES Soft X-ray Flares"]

[5] [https://ui.adsabs.harvard.edu/abs/2025ApJ...979L..16T "The Occurrence of Powerful Flares Stronger than X10 Class in Solar Cycles"]

SolarNuggets

2026-05-20T06:45:19Z

Hhudson:

Welcome to the [[SolarNuggets]] collection, which extends the series of [[RHESSI]] Nuggets. The following is a time-ordered list of the latest Nuggets added to the HelioWiki. An [[:Category:Nugget|alphabetical list of the SolarNuggets]] is also available as well as [[:Category:RHESSI Nugget List|yearly lists]]. One can search on author, topic, IAU flare identifier, etc.). We welcome volunteer authors - please see our page of [[Help:For_Authors| help for authors]] or just send an email to the Curator at (hugh.hudson@glasgow.ac.uk).

{{Nugget Badge
|title = X-ray Log Letters‎‎
|number = 526
|first_author = Hugh HUDSON
|second_author = and Ed CLIVER
||publish_date = 18 May 2026
|description = Replacing ..ABCMX.. with a new - comprehensive and quantitative - "QSabcmxyz" catalog
|image=Icon526.png}}

{{Nugget Badge
|title = How Extreme Can Solar Flares Get? A Statistical View‎‎
|number = 525
|first_author = Lapo Ceccarelli
|second_author = and Daniela CASTRO-CAMILO
||publish_date = 4 May 2026
|description = A proper statistical treatment of the prospects for an extreme solar flare event
|image=Icon525.png}}

{{Nugget Badge
|title = Observations of Slow Elemental Abundance Decay in Association to CME
|number = 524
|first_author = Saara TAKALA
||publish_date = 27 April 2026
|description = Soft X-ray spectroscopy tracks coronal abundance variations associated with a CME
|image=Icon524.png}}

{{Nugget Badge
|title = An Unusual Long-Lived Radio Burst Oscillating in Frequency
|number = 523
|first_author = Marian KARLICKÝ,
|second_author = Robert SYCH and Alena ZEMANOVÁ
||publish_date = 20 April 2026
|description = Remarkable decimetric signatures of structured outflows from a flaring active region
|image=Icon523.png}}

{{Nugget Badge
|title = Lateral Deformation of Large-scale Coronal Mass Ejections during the Transition from Nonradial to Radial Propagation
|number = 522
|first_author = Huidong HU
||publish_date = 13 April 2026
|description = Coronal mass ejections can begin their trajectory highly tilted to the vertical, but then straighten out
|image=Icon522.png}}

{{Nugget Badge
|title = Can EUV Power-Spectral Indices Reveal Imminent Solar Flares?
|number = 521
|first_author = Sihui ZHONG,
|second_author = Dmitrii KOLOTKOV and Valery M. NAKARIAKOV
||publish_date = 6 April 2026
|description = A new flare-precursor observable - power spectra
|image=Icon521.png}}

{{Nugget Badge
|title = How energetic can solar flares become?
|number = 520
|first_author = Natalie KRIVOVA
||publish_date = 31 March 2026
|description = The history of active-region areas suggests the possibility of solar superflares
|image=Icon520.png}}

{{Nugget Badge
|title = Hinode EIS Observations of Plasma Composition Evolution and Radiative Cooling of Flare Loops
|number = 519
|first_author = Teodora MIHĂILESCU,
|second_author = Peter YOUNG et AL.
||publish_date = 16 March 2026
|description = Higher FIP bias than expected in some flare loops, a diagnostically interesting result
|image=Icon519.png}}

{{Nugget Badge
|title = When Magnetic Field Lines Stretch, Snap, and Expand: A New Look at Solar Flares with L-maps
|number = 518
|first_author = Maria KAZACHENKO,
|second_author = Yuhong FAN and Andrey AFANASYEV
||publish_date = 9 March 2026
|description = A clever new tool tracks magnetic connectivity (and energy) during flare/CME occurrence
|image=Icon518.png}}

{{Nugget Badge
|title = Observational Evidence Linking Loop Length and Thermal/Nonthermal Peak Timing in Solar Flares
|number = 517
|first_author = Solomon PERRIYIL
||publish_date = 23 February 2026
|description = Clear evidence for the universality of the physics behind the Neupert Effect
|image=Icon517.png}}

{{Nugget Badge
|title = A fine-scale bright kernel captured by Hi-C 3 in the post-maximum phase of an M-class solar flare
|number = 516
|first_author = Sanjiv TIWARI
||publish_date = 9 February 2026
|description = The Hi-C rocket catches an extremely compact brightening in late-phase flare ribbon development
|image=Icon516.png}}

{{Nugget Badge
|title = On the Relationship Between Nanoflare Energy and Delay in the Closed Solar Corona
|number = 515
|first_author = Shanwlee SOW MONDAL et al.
||publish_date = 19 January 2026
|description = Nanoflaring implies energy storage and sudden release, suggesting correlation between event energy and its timing
|image=Icon515.png}}

{{Nugget Badge
|title = Fine structures in solar flare ribbons
|number = 514
|first_author = Jonas THOEN FABER
||publish_date = 12 January 2026
|description = Elongated "riblets" commonly rise out of flare ribbons, and have characteristic Doppler shifts
|image=Icon514.png}}

{{Nugget Badge
|title = The M- and X-class White-light Flares in Super Active Region NOAA 13664/13697
|number = 513
|first_author = Zhichen JING
|second_author = and Ying LI
|publish_date = 5 January 2026
|description = "Super" active regions have relatively more frequent X-class flares, which correlate well with visible continuum (white-light flare) emission
|image=Icon513.png}}

{{Nugget Badge
|title = Iron Fluorescence in X-class Solar Flares
|number = 512
|first_author = Abhilash SARWADE
|publish_date = 8 December 2025
|description = A new spectroscopic capability for Iron K-alpha fluorescence
|image=Icon512.png}}

{{Nugget Badge
|title = Sun-as-a-star Analysis of a Solar Eruption Source Region Using H-alpha Spectroscopic Observations from CHASE
|number = 510
|first_author = Xiaofeng LIU
|second_author = and Yijun HOU
|publish_date = 24 November 2025
|description = Sun-as-a-star observations help to translate solar/stellar processes
|image=Icon5010.png}}

{{Nugget Badge
|title = On the Origin of Solar Long-Duration Gamma-Ray Flares‎‎‎‎
|number = 509
|first_author = Alessandro BRUNO
|publish_date = 3 November 2025
|description = Do we really need a CME to produce a long-duration solar gamma-ray event?
|image=Icon509.png}}

{{Nugget Badge
|title = FAI and GOES eclipses‎‎
|number = 508
|first_author = Hugh HUDSON
|publish_date = 20 October 2025
|description = Flare anticipation via FAI may have problems during GOES eclipses, which are really interesting in their own right
|image=Icon508.png}}

{{Nugget Badge
|title = The EUV Late Phase‎
|number = 507
|first_author = Sascha ORNIG
|publish_date = 13 October 2025
|description = Basic comparative statistics of the ELP, a distinct flare phenomenon
|image=Icon507.png}}

{{Nugget Badge
|title = Time evolution of flare-accelerated electrons using the warm-target model‎
|number = 506
|first_author = Debesh BHATTACHARJEE
|publish_date = 6 October 2025
|description = Considering a "warm" thick target allows flare-accelerated electrons to be treated self-consistently
|image=Icon506.png}}

{{Nugget Badge
|title = SOLSTICE observes flare Doppler shifts in Si III
|number = 505
|first_author = Luke MAJURY
|publish_date = 30 September 2025
|description = A rarely used database suggests prograde-flow Doppler shifts in flaring plasmas
|image=Icon505.png}}

{{Nugget Badge
|title = Flare Phases and the Earth's Ionospheric Response
|number = 504
|first_author = Susanna BEKKER
|publish_date = 16 September 2025
|description = A flare's "EUV late phase" is surprisingly geoeffective
|image=Icon504.png}}

{{Nugget Badge
|title = Neupertianity
|number = 503
|first_author = Hugh HUDSON
|publish_date = 25 August 2025
|description = It's hard to avoid the Neupert Effect
|image=Icon503.png}}

{{Nugget Badge
|title = Synchrotron Radiation and the Foundations for a Cosmic Bridge
|number = 502
|first_author = Immanuel JEBARAJ
|publish_date = 11 August 2025
|description = Gyrosynchrotron radiation in shocks: a cosmic connection
|image=Icon502.png}}

{{Nugget Badge
|title = The Aulanier Effect: drifting footpoints of CME flux ropes
|number = 501
|first_author = Jaroslav DUDÍK,
|second_author = Juraj LÖRINČÍK and Brigitte SCHMIEDER
|publish_date = 21 July 2025
|description = The breakthrough to 3D flare physics: the Aulanier Effect
|image=Icon501.png}}

{{Nugget Badge
|title = Five Hundred Nuggets
|number = 500
|first_author = Hugh HUDSON
|publish_date = 14 July 2025
|description = A milestone
|image=Icon169.png}}

{{Nugget Badge
|title = Quasiperiodic Pulsations in the Balmer Continuum in an X-class Solar White-light Flare
|number = 499
|first_author = De-Chao SONG et al.
|publish_date = 30 June 2025
|description = QPP in the Balmer continuum: the powerful heartbeat of a flare
|image=Icon499.png}}

{{Nugget Badge
|title = High-Resolution Observations of a C3 class White-Light Flare
|number = 498
|first_author = Zhe XU and
|second_author = Xiaoli YAN
|publish_date = 16 June 2025
|description = A compact white-light flare with vortical motions (and hard X-rays)
|image=Icon498.png}}

{{Nugget Badge
|title = The Sun's open-closed flux boundary and the origin of the slow solar wind
|number = 497
|first_author = Chloe WILKINS and
|second_author = David PONTIN
|publish_date = 26 May 2025
|description = Identifying the solar sources of slow solar wind
|image=Icon497.png}}

{{Nugget Badge
|title = Delay of Near-Relativistic Electrons
|number = 496
|first_author = Grant MITCHELL
|publish_date = 19 May 2025
|description = Parker Solar Probe solves an old mystery about type III bursts
|image=Icon496.png}}

{{Nugget Badge
|title = A Multi-Site Telescope for Multi-Height for Synoptic Observations
|number = 495
|first_author = Fallon KONOW
|publish_date = 11 May 2025
|description = A new synoptic network for observations at multiple wavelengths
|image=Icon495.png}}

{{Nugget Badge
|title = On turbulent magnetic reconnection: fast and slow mean steady-states
|number = 494
|first_author = Sage STANISH
|second_author = and David MacTAGGART
|publish_date = 28 April 2025
|description = In a turbulent medium, magnetic reconnection has two limiting domains
|image=Icon494.png}}

{{Nugget Badge
|title = Quasi-Periodic Pulsations in Ionospheric TEC and Flare EUV
|number = 493
|first_author = Aisling O'HARE
|publish_date = 21 April 2025
|description = The Earth's ionosphere reflects QPPs, with a small delay
|image=Icon493.png}}

{{Nugget Badge
|title = Metis observations of Alfvenic outflows driven by interchange reconnection in a pseudostreamer
|number = 492
|first_author = Paolo ROMANO and the Metis team
|publish_date = 7 April 2025
|description = Exactly as predicted by numerical simulations... a rare coup
|image=Icon492.png}}

{{Nugget Badge
|title = Solar Rollercoaster: looping-the-loop in the solar corona
|number = 491
|first_author = Mohamed NEDAL et al.
|publish_date = 31 March 2025
|description = Large-scale helical motion in the flare/CME SOL2024-05-14
|image=Icon491.png}}

{{Nugget Badge
|title = Proton Beam Energy Deposition as a Mechanism of Deep Photospheric Heating
|number = 490
|first_author = Samuel GRANOVSKY
|second_author = and Alexander KOSOVICHEV
|publish_date = 17 March 2025
|description = Evidence for proton beams in white-light flares
|image=Icon490.png}}

{{Nugget Badge
|title = New insights into the proton precipitation sites in solar flares
|number = 489
|first_author = Andrea Francesco BATTAGLIA
|second_author = and Säm KRUCKER
|publish_date = 17 February 2025
|description = There is no detectable difference in proton and electron foopoint locations after all
|image=Icon489.png}}

{{Nugget Badge
|title = Solar Gamma-Ray Evidence for a Distinct Population of MeV Flare-Accelerated Electrons
|number = 488
|first_author = Gerry SHARE
|second_author =
|publish_date = 10 February 2025
|description = Relativistic electrons in solar flares newly recognized as a distinct process
|image=Icon488.png}}

{{Nugget Badge
|title = From Chromospheric Evaporation to Coronal Rain: An Investigation of the Mass and Energy Cycle of a Flare‎
|number = 487
|first_author = Seray &Scedil;AHIN
|second_author = and Patrick ANTOLIN
|publish_date = 3 February 2025
|description = A first quantitative comparison of flare evaporation and coronal rain
|image=Icon487.png}}

{{Nugget Badge
|title = Energetic neutral atoms detected in the large solar energetic particle event of February 2022‎
|number = 486
|first_author = Christina COHEN
|second_author =
|publish_date = 20 January 2025
|description = Only the second direct observation of high-energy neutral atoms from the Sun
|image=Icon486.png}}

{{Nugget Badge
|title = Magnetic topology of quiet-Sun Ellerman bombs and associated ultraviolet brightenings‎
|number = 485
|first_author = Aditi BHATNAGAR
|second_author =
|publish_date = 6 January 2025
|description = Tiny "Ellerman Bombs" occur all across the solar surface, with differences
|image=Icon485.png}}

{{Nugget Badge
|title = Unveiling CME Dynamics: Rare Rotations of CMEs in the Heliosphere
|number = 484
|first_author = Sandeep KUMAR and
|second_author = Nandita SRIVASTAVA
|publish_date = 30 December 2024
|description = CMEs usually do not show additional rotation as they move though the heliosphere
|image=Icon484.png}}

{{Nugget Badge
|title = Spatial and Spectral Evolution of Microwave and X-Ray Sources During the Limb Flare SOL2023-02-05
|number = 483
|first_author = Yulia N. SHAMSUTDINOVA
|publish_date = 23 December 2024
|description = Rare microwave imaging spectroscopy of a hot-onset precursor event
|image=Icon483.png}}

{{Nugget Badge
|title = High-resolution observational analysis of flare ribbon fine structures
|number = 482
|first_author = Jonas THOEN FABER
|publish_date = 16 December 2024
|description = Spatially periodic fine structures in flare ribbons reveal current-sheet tearing
|image=Icon482.png}}

{{Nugget Badge
|title = Advection and super-diffusive expansion as the model of flare accelerated electron transport in type III solar radio bursts
|number = 481
|first_author = Eduard KONTAR
|publish_date = 9 December 2024
|description = Sturrock's dilemma resolved
|image=Icon481.png}}

{{Nugget Badge
|title = Faraday's Law in Solar Flares: A Cautionary Message
|number = 480
|first_author = Michael FARADAY
|publish_date = 2 December 2024
|description = We must not forget the global implications of Faraday's Law
|image=Icon480.png}}

{{Nugget Badge
|title = Remarkable NUV Spectrum of an M-star Megaflare
|number = 479
|first_author = Adam KOWALSKI
|publish_date = 25 November 2024
|description = Remarkable NUV spectra from an HST stellar flare
|image=Icon479.png}}

{{Nugget Badge
|title = Revised Point-Spread Functions of AIA and their effect on DEM analyses
|number = 478
|first_author =Stefan HOFMEISTER,
|second_author = Daniel Wolf SAVIN, and Michael HAHN
|publish_date = 18 November 2024
|description = Substantial revisions of the AIA point-response functions
|image=Icon478.png}}

{{Nugget Badge
|title = How much of the energy in flare-accelerated electrons reaches the chromosphere?
|number = 477
|first_author = Meriem ALAOUI
|second_author = and Gordon HOLMAN
|publish_date = 11 November 2024
|description = Keeping flare-accelerated electrons out of the chromosphere
|image=Icon477.png}}

{{Nugget Badge
|title = Spatially resolved plasma composition evolution in a solar flare
|number = 476
|first_author = Andy S. H. TO
|publish_date = 4 November 2024
|description = Reconnection outflow feeds abundance variations
|image=Icon476.png}}

{{Nugget Badge
|title = HOPE during high activity
|number = 475
|first_author = Hugh HUDSON
|second_author = and Alphonse STERLING
|publish_date = 28 October 2024
|description = Hot onsets appear even in the most active solar conditions
|image=Icon475.png}}

{{Nugget Badge
|title = Simulated heliospheric electron spectra show sensitivity to plasma properties of a source region in the flaring corona
|number = 474
|first_author = Ross PALLISTER
|second_author = and Natasha JEFFREY
|publish_date = 21 October 2024
|description = Getting closer to an understanding of how solar energetic particles "escape"
|image=Icon474.png}}

{{Nugget Badge
|title = An extremely complex active region with very strong non-neutralized electric currents
|number = 473
|first_author = Ioannis KONTOGIANNIS
|publish_date = 14 October 2024
|description = Large non-neutralized electric currents flow through the active-region corona
|image=Icon473.png}}

{{Nugget Badge
|title = An X9 flare and its huge crochet (SFE)
|number = 472
|first_author = Hugh HUDSON
|publish_date = 7 October 2024
|description = The geomagnetic effect (SFE/crochet) that will calibrate the Carrington flare
|image=Icon472.png}}

{{Nugget Badge
|title = All microflares that accelerate electrons to high energies are rooted in sunspots
|number = 471
|first_author = Andrea Francesco BATTAGLIA
|publish_date = 30 September 2024
|description = Microflares with hard X-ray spectra are a well-defined class, and invariably have one footpoint embedded in a sunspot
|image=Icon471.png}}

{{Nugget Badge
|title = The warm-target model and kappa distributions
|number = 470
|first_author = Yingjie LUO
|publish_date = 16 September 2024
|description = A self-consistent treatment of non-thermal electron spectra points to kappa distributions
|image=Icon470.png}}

{{Nugget Badge
|title = Is there HOPE for Hyder flares...
|number = 468
|first_author = Hugh HUDSON
|publish_date = 15 March 2024
|description = Filament eruptions/Hyder flares/disparitions brusques may all show HOPE
|image=Icon468.png}}

{{Nugget Badge
|title = Sun-as-a-star Analysis of the M8.7 Flare on 2022 October 2 Using H-alpha and EUV Spectra Taken by SMART/SDDI and SDO/EVE
|number = 467
|first_author = Takato OTSU
|publish_date = 19 February 2024
|description = Whole-Sun spectroscopic observations can readily detect ejecta
|image=Icon467.png}}

{{Nugget Badge
|title = Unexpected Asymmetry in GeV Emission
|number = 466
|first_author = Bruno ARSIOLI and Elena ORLANDO
|publish_date = 15 January 2024
|description = The high-energy solar gamma radiation shows inexplicable but fascinating properties
|image=Icon466.png}}

{{Nugget Badge
|title = When it rippled in one place and exploded in another
|number = 465
|first_author = Ivan ZIMOVETS
|publish_date = 25 December 2023
|description = Pulsations precede a flare, but seem unrelated
|image=Icon465.png}}

{{Nugget Badge
|title = Solar flares: evaporation and simulation‎
|number = 464
|first_author = Malcolm DRUETT
|publish_date = 18 December 2023
|description = Fitting beam electrons into multi-dimensional models
|image=Icon464.png}}

{{Nugget Badge
|title = Pre-impulsive and Impulsive Phases of the March 28, 2022 Sub-Terahertz Flare
|number = 463
|first_author = Galina G. MOTORINA
|publish_date = 11 December 2023
|description = A flare with an increasing sub-THz spectrum and sub-THZ precursor information
|image=Icon463.png}}

{{Nugget Badge
|title = Coronal Bright Points
|number = 462
|first_author = Daniel NÓBREGA-SIVERIO
|publish_date = 27 November 2023
|description = Bright EUV rowel-like structures can result from null-point reconnection
|image=Icon462.png}}

{{Nugget Badge
|title = Aurora-like Radio Emission from a Sunspot
|number = 461
|first_author = Sijie YU
|publish_date = 20 November 2023
|description = Maser action above a sunspot
|image=Icon461.png}}

{{Nugget Badge
|title = Search for a Flare Anticipation Index (FAI)
|number = 460
|first_author = Hugh HUDSON
|second_author = and Jim McTiernan
|publish_date = 13 November 2023
|description = Quantifying flare precursors on a few-minute time scale
|image=Icon460.png}}

{{Nugget Badge
|title = Bouncing motions of fast electrons using Nobeyama Radioheliograph
|number = 459
|first_author = Keitarou MATSUMOTO
|publish_date = 6 November 2023
|description = Solar evidence for conservation of second adiabatic invariant in particle motion
|image=Icon459.png}}

{{Nugget Badge
|title = Impact of nanoflare heating in the lower solar atmosphere
|number = 458
|first_author = Helle BAKKE
|publish_date = 30 October 2023
|description = The behavior of nanoflare fast electrons in Bifrost models
|image=Icon458.png}}

{{Nugget Badge
|title = Precise timing of flare footpoint sources from mid-infrared observations‎
|number = 457
|first_author = Paulo SIMÕES et al.
|publish_date = 23 October 2023
|description = Mid-IR observations at high spatial and high temporal resolution: Conjugacy
|image=Icon457.png}}

{{Nugget Badge
|title = The Greatest GOES Flares‎
|number = 456
|first_author = Hugh HUDSON
|second_author = and Ed CLIVER
|publish_date = 25 September 2023
|description = The greatest GOES events, re-analyzed, fall short of expectations
|image=Icon456.png}}

{{Nugget Badge
|title = Introducing SunSketcher
|number = 455
|first_author = Hugh HUDSON
|second_author = and Gordon EMSLIE
|publish_date = 11 September 2023
|description = Galloping towards roundup in the 2024 total solar eclipse
|image=Icon455.png}}

{{Nugget Badge
|title = TeV Gamma rays from the Quiescent Sun
|number = 454
|first_author = Mehr Un NISA
|second_author = and John BEACOM
|publish_date = 21 August 2023
|description = Solar photons at unprecedented high energies
|image=Icon454.png}}

{{Nugget Badge
|title = Temporal and Spatial Characteristics of Hard X-Ray Sources in Flare Model with Vertical Current Sheet
|number = 453
|first_author = Alexander SHABALIN, Eugenia OVCHINNIKOVA,
|second_author = and Yuri CHARIKOV
|publish_date = 7 August 2023
|description = Modeling betatron acceleration in current-sheet development.
|image=Icon453.png}}

{{Nugget Badge
|title = Spatial Distribution of Magnetic Reconnection Rate in an M6.5 Solar Flare
|number = 452
|first_author = Ju JING
|publish_date = 12 June 2023
|description = Linking hard X-rays to high-resolution images that show reconnection rates.
|image=Icon452.png}}

{{Nugget Badge
|title = Statistical study of Type III bursts and associated HXR emissions
|number = 451
|first_author = Nicole VILMER and Tomin JAMES
|publish_date = 29 May 2023
|description = Linking electron populations escaping from the Sun with those that RHESSI detects.
|image=Icon451.png}}

{{Nugget Badge
|title = Solar flare hard X-rays from the anchor points of an eruptive filament
|number = 450
|first_author = Muriel STIEFEL
|publish_date = 15 May 2023
|description = A rare "four-ribbon" flare has been detected in hard X-rays.
|image=Icon450.png}}

{{Nugget Badge
|title = Did a Solar Flare Accelerate all the Ambient Electrons in the Coronal Acceleration Region?...
|number = 449
|first_author = Gordon EMSLIE, Eduard KONTAR,
|second_author = Galina MOTORINA, and Brian DENNIS
|publish_date = 1 May 2023
|description = Considering SOL2017-09-10, probably not.
|image=Icon449.png}}

{{Nugget Badge
|title = Diagnostics of Spatially-Extended Turbulent Acceleration and Transport
|number = 448
|first_author = Morgan STORES
|publish_date = 24 April 2023
|description = Drilling down into the detailed structure of solar-flare energy release by including turbulence with particle acceleration.
|image=Icon448.png}}

{{Nugget Badge
|title = RHESSI's Re-entry
|number = 447
|first_author = Pascal SAINT-HILAIRE and
|second_author = Hugh HUDSON
|publish_date = 17 April 2023
|description = The final demise of RHESSI is this week
|image=Icon447.png}}

{{Nugget Badge
|title = A Glasgow geomagnetic observation of a solar flare
|number = 446
|first_author = Hugh HUDSON, John MALONE-LEIGH,
|second_author = Graham WOAN, and Chris OSBORNE
|publish_date = 13 March 2023
|description = Irish and Scottish geomagnetic observatories see a crochet much like that of the Carrington event
|image=Icon_446.png}}

{{{Nugget Badge
|title = Particle Acceleration in Two Coronal Jets
|number = 445
|first_author = Yixian ZHANG
|publish_date = 27 February 2023
|description = Coronal jets with hard X-ray sources at disjoint locations
|image=Icon445.png}}

{{Nugget Badge
|title = The Curious First Sunquake of Solar Cycle 25‎
|number = 444
|first_author = Alexander KOSOVICHEV
|publish_date = 13 February 2023
|description = A double whammy: two distinct sunquakes from SOL2022-05-10.
|image=Icon444.png}}

{{Nugget Badge
|title = Hard X-ray Pulsations via Gaussian Decomposition
|number = 443
|first_author = Hannah COLLIER and Laura HAYES
|publish_date = 30 January 2023
|description = Flare hard X-ray time variations decomposed objectively
|image=Icon443.png}}

{{Nugget Badge
|title = A possible coronal magnetic flare precursor
|number = 442
|first_author = Enrico LANDI
|publish_date = 16 January 2023
|description = Novel measurements of the coronal magnetic field may help with flare prediction
|image=Icon442.png}}

{{Nugget Badge
|title = A slow HOPE with microwave context
|number = 441
|first_author = Hugh HUDSON
|publish_date = 12 December 2022
|description = A new microwave facility at Chashan Observatory, and a prototypical HOPE
|image=Icon441.png}}

{{Nugget Badge
|title = Rapid variations of Si IV spectra in a flare observed by IRIS at a sub-second cadence
|number = 440
|first_author = Juraj LÖRINČÍK
|publish_date = 14 November 2022
|description = Transition-region lines in a flare have a Doppler component revealing quasi-periodic pulsations
|image=Icon440.png}}

{{Nugget Badge
|title = A Significant Sudden Ionospheric Disturbance Associated with a Massive Gamma-ray Burst
|number = 439
|first_author = Laura HAYES and Peter GALLAGHER
|publish_date = 31 October 2022
|description = A first SID observed in broad daylight, from a source far far away
|image=Icon439.png}}

{{Nugget Badge
|title = Effects of Coronal Structures on the Dynamics of the Global Coronal Wave of SOL2017-09-10‎
|number = 438
|first_author = Huidong HU, Ying D. LIU, and Bei ZHU
|publish_date = 17 October 2022
|description = The amazing global coronal wave of SOL2017-09-10 wrapped around the whole Sun, and displayed transmission and reflection at both polar coronal holes
|image=Icon438.png}}

{{Nugget Badge
|title = KW-Sun: The Konus-Wind Solar Flare Database in Hard X-Ray and Soft Gamma-Ray Ranges
|number = 437
|first_author = Alexandra LYSENKO
|publish_date = 26 September 2022
|description = An unrivaled hard X-ray and gamma-ray database is entering its third activity maximum
|image=Icon437.png}}

{{Nugget Badge
|title = First Detection of Kink Oscillations with Solar Orbiter
|number = 436
|first_author = Sihui ZHONG et al.
|publish_date = 19 September 2022
|description = SolO sees coronal oscillations as well as AIA can, and even better
|image=Icon436.png}}

{{Nugget Badge
|title = Energetic Neutral Hydrogen from Large Solar Flares
|number = 435
|first_author = Glenn MASON
|publish_date = 6 September 2022
|description = A rediscovered data treasury reveals the occurrence of many flare/CME events producing solar high-energy neutral atoms
|image=Icon435.png}}

{{Nugget Badge
|title = Fifty-year Anniversary of the First Detection of Gamma rays from a Solar Flare
|number = 434
|first_author = Jim Ryan,
|second_author = Brian Dennis, and Phil Dunphy
|publish_date = 8 August 2022
|description = The rich astrophysics of gamma-ray astronomy began with solar observations fifty years ago
|image=Icon434.png}}

{{Nugget Badge
|title = Fast Prograde Flows in Solar Active Regions
|number = 433
|first_author = Hugh HUDSON
|publish_date = 25 July 2022
|description = Unexpected, unpredicted, and not modeled yet - weird flows in hot active-region loops
|image=Icon433.png}}

{{Nugget Badge
|title = Undetected Minority-polarity Flux, Moss, and Coronal Heating
|number = 432
|first_author = Yi-Ming WANG
|publish_date = 11 July 2022
|description = There's plenty of room in "unipolar" active regions for both polarities, and there is good evidence for them
|image=Icon432.png}}

{{Nugget Badge
|title = Thermal/Nonthermal with MinXSS and RHESSI
|number = 431
|first_author = Shunsaku NAGASAWA
|publish_date = 13 June 2022
|description = Time-domain studies of improved X-ray spectra reveal a "super-hot' component
|image=Icon431.png}}

{{Nugget Badge
|title = Sun-as-a-star spectroscopic observations of the line-of-sight velocity of a solar eruption on October 28, 2021
|number = 430
|first_author = Yu XU
|second_author = and Hui TIAN
|publish_date = 30 May 2022
|description = The observation of the full 3d velocity of a CME, for an anniversary event
|image=Icon430.png}}

{{Nugget Badge
|title = Carl Størmer
|number = 429
|first_author = Hugh HUDSON
|second_author = and Lyndsay FLETCHER
|publish_date = 15 April 2022
|description = Størmer and the theory of trapping in loops
|image=Icon429.png}}

{{Nugget Badge
|title = Solar Hard X-rays with Insight
|number = 428
|first_author = Wei WANG
|second_author = and Ping ZHANG
|publish_date = 21 March 2022
|description = A spectacular limb flare introduces Insight/HXMT, a new observational resource
|image=Icon428.png}}

{{Nugget Badge
|title = Probing chromospheric current sheets using SST and ALMA co-observations
|number = 427
|first_author = João da SILVA SANTOS
|publish_date = 21 February 2022
|description = Emerging magnetic flux appears in ALMA images reflecting coronal current sheets
|image=Icon427.png}}

{{Nugget Badge
|title = A demonstration of STIX hard X-ray imaging spectroscopy capabilities for an X-class flare (SOL2021-10-28)
|number = 426
|first_author = Andrea BATTAGLIA, Hannah COLLIER,
|second_author = and Säm KRUCKER
|publish_date = 7 February 2022
|description = STIX imaging of an X-class flare marks its success
|image=Icon426.png}}

{{Nugget Badge
|title = A solar flare driven by thermal conduction observed in mid-infrared
|number = 425
|first_author = Guillermo GIMÉNEZ de CASTRO
|publish_date = 24 January 2022
|description = Strong 10-micron emission from a GOES C2 flare suggests conductive heating
|image=Icon425.png}}

{{Nugget Badge
|title = Disk Occultation of a Lopsided Sun‎
|number = 424
|first_author = Hugh HUDSON,
|second_author = Stephen WHITE and Säm KRUCKER
|publish_date = 10 January 2022
|description = Observing a spotless Sun can enable observations of the faint corona.
|image=Icon424.png}}

{{Nugget Badge
|title = Resolving two distinct thermal X-ray components in a compound solar flare
|number = 423
|first_author = Zhenjun ZHOU
|second_author = and Rui LIU
|publish_date = 28 December 2021
|description = Superhot coronal sources may be independent loop systems
|image=Icon423.png}}

{{Nugget Badge
|title = Bridging solar flares to coronal mass ejections
|number = 422
|first_author = Markus ASCHWANDEN
|publish_date = 14 December 2021
|description = The Neupert effect allows us to trace coronal mass ejections seamlessly
|image=Icon422.png}}

{{Nugget Badge
|title = The Jakimiec Diagnostic Diagram
|number = 421
|first_author = Hugh HUDSON
|publish_date = 29 November 2021
|description = The joint variation of GOES temperature and emission measure discloses new features via an old tool
|image=Icon421.png}}

{{Nugget Badge
|title = First look at ALMA/HInode/IRIS microflares
|number = 420
|first_author = Toshifumi SHIMIZU
|second_author = et al.
|publish_date = 8 November 2021
|description = High-resolution ALMA and multiwavelength observations of microflaring
|image=Icon420.png}}

{{Nugget Badge
|title = Thomson scattering near sunspots
|number = 419
|first_author = Pascal Saint-Hilaire
|second_author = et al.
|publish_date = 25 October 2021
|description = Completing the modeling of low-coronal Thomson polarimetry
|image=Icon419.png}}

{{Nugget Badge
|title = A Non-PFSS Global Coronal Model
|number = 418
|first_author = Oliver RICE
|second_author = and Anthony YEATES
|publish_date = 11 October 2021
|description = Modeling as convenient as PFSS but much more realistic
|image=Icon418.png}}

{{Nugget Badge
|title = Manifold Nonthermality
|number = 417
|first_author = Marina BATTAGLIA
|second_author = et al.
|publish_date = 27 September 2021
|description = Even weak flares involve multiple sites of non thermal activity
|image=Icon417.png}}

{{Nugget Badge
|title = X-Rays from a Type I Radio Burst
|number = 416
|first_author = R. RAMESH
|publish_date = 20 September 2021
|description = A first identification of type I radio emission with hot plasma
|image=Icon416.png}}

{{Nugget Badge
|title = Do Hot Onsets Predict Flare Magnitudes?
|number = 415
|first_author = Hugh HUDSON
|publish_date = 30 August 2021
|description = Maybe we can tell how big a flare is going to be from its initial development...
|image=Icon415.png}}

{{Nugget Badge
|title = Confined or Eruptive?
|number = 414
|first_author = Ting LI et al.
|publish_date = 16 August 2021
|description = Increased magnetic flux reduces CME eruptivity
|image=Icon414.png}}

{{Nugget Badge
|title = Impulsive and Gradual Eruptive Gamma Flares and Associated CMEs
|number = 413
|first_author = Alexey STRUMINSKY,
|second_author = Irina GRIGORIEVA and Andrei SADOVSKI
|publish_date = 19 July 2021
|description = Extreme behavior of flare/CME events explained by environment
|image=Icon373.png}}

{{Nugget Badge
|title = The Morphology of Flare Time Profiles
|number = 412
|first_author = Larisa KASHAPOVA
|second_author = et al.
|publish_date = 12 July 2021
|description = Systematic comparison of solar and stellar flaring time profiles
|image=Icon412.png}}

{{Nugget Badge
|title = Flare Pulsation and the Heliosphere
|number = 411
|first_author = Brendan CLARKE
|second_author = et al.
|publish_date = 5 July 2021
|description = Flare pulsations link closely to the distant heliosphere
|image=Icon411.png}}

{{Nugget Badge
|title = STIX, the Hard X-Ray Telescope on board Solar Orbiter
|number = 410
|first_author = Andrea Francesco BATTAGLIA
|second_author = and Säm KRUCKER
|publish_date = 28 June 2021
|description = STIX is operational and producing great data
|image=Icon410.png}}

{{Nugget Badge
|title = Nonequilibrium Ionization of Flare Plasma Observed by Hinode/EIS
|number = 409
|first_author = Shinsuke IMADA
|second_author =
|publish_date = 14 June 2021
|description = Evidence for non-equilibrium ionization in the current sheet of SOL2017-09-10
|image=Icon409.png}}

{{Nugget Badge
|title = Effects of Flares on Solar p-modes
|number = 408
|first_author = Maria-Cristina RABELLO SOARES
|second_author = and Frederic BAUDIN
|publish_date = 26 April 2021
|description = No detectable p-mode amplitude changes due to solar flares
|image=Icon408.png}}

{{Nugget Badge
|title = Subsecond Spikes in Solar Flare X-ray Flux as Seen by Fermi GBM
|number = 407
|first_author =Trevor KNUTH
|second_author = and Lindsay GLESENER
|publish_date = 19 April 2021
|description = A new analysis technique pushes hard X-ray time scales to 0.1 sec or faster
|image=Icon407.png}}

{{Nugget Badge
|title = Negative He 10830 Flare Ribbons and Non-thermal Electrons
|number = 406
|first_author = Graham KERR
|second_author =
|publish_date = 12 April 2021
|description = A 1D radiation hydrodynamics model can explain the dark leading edges of He I flare ribbons
|image=Icon406.png}}

{{Nugget Badge
|title = Tracing the sources of gradual solar energetic particle events
|number = 405
|first_author = David H. BROOKS
|second_author = and Stephanie L. YARDLEY
|publish_date = 29 March 2021
|description = Chemical abundances in SEPs suggest an origin in flare-related moss regions
|image=Icon405.png}}

{{Nugget Badge
|title = The Superflare SOL2017-09-06: from submm to mid-IR
|number = 404
|first_author = Guillermo (Guigue) GIMÉNEZ DE CASTRO
|second_author =
|publish_date = 15 March 2021
|description = Glimpsing the "missing decades" of the flare emission spectrum
|image=Icon404.png}}

{{Nugget Badge
|title = The Neupert Effect Revisited
|number = 403
|first_author = Jiong QIU
|second_author =
|publish_date = 8 March 2021
|description = Two time scales for heating individual flare strands
|image=Icon403.png}}

{{Nugget Badge
|title = FLUKA as a tool for interpreting flare gamma-rays
|number = 402
|first_author = Alec MACKINNON
|second_author =
|publish_date = 1 March 2021
|description = The nuclear physics of solar flares captured in a detailed model
|image=Icon402.png}}

{{Nugget Badge
|title = A Collective Study of 11 NuSTAR Microflares
|number = 401
|first_author = Jessie DUNCAN and
|second_author = Lindsay GLESENER
|publish_date = 22 February 2021
|description = Swarms of NuSTAR micro flares
|image=Icon401.png}}

{{{{Nugget Badge
|title = A Solar FRB
|number = 400
|first_author = Dale GARY and
|second_author = Hugh HUDSON
|publish_date = 15 February 2021
|description = A new frontier in the solar time domain
|image=Icon400.png}}

{{Nugget Badge
|title = Richard Schwartz
|number = 399
|first_author = Brian DENNIS and
|second_author = Hugh HUDSON
|publish_date = 25 January 2021
|description = Remembering a friend and colleague
|image=Icon399.jpg}}

{{Nugget Badge
|title = Observing Solar Flare X-ray Polarization with Prospective CubeSat Missions
|number = 398
|first_author = Natasha JEFFREY
|publish_date = 4 January 2021
|description = The polarization of the solar X-ray spectrum generally remains to be observed
|image=Icon398.png}}

{{Nugget Badge
|title = Solar effects in the local interstellar medium
|number = 397
|first_author = Don GURNETT and
|second_author = Hugh HUDSON
|publish_date = 14 December 2020
|description = Relativistic particle events observed _in situ_ in the interstellar medium
|image=Icon397.png}}

{{Nugget Badge
|title = Investigation of Small-Scale Energy Releases in Hard X-rays with FOXSI
|number = 396
|first_author = Subramania ATHIRAY and
|second_author = Juliana VIEVERING
|publish_date = 7 December 2020
|description = Hard X-rays and high temperatures from the feeblest microflares
|image=Icon396.png}}

{{Nugget Badge
|title = What drives impulsive coronal heating?
|number = 395
|first_author = Pradeep CHITTA
|second_author = et al.
|publish_date = 30 November 2020
|description = Impulsive footpoint emissions suggest magnetic reconnection in the chromosphere
|image=Icon395.png}}

{{Nugget Badge
|title = Probing the solar coronal heating function with slow magnetoacoustic waves
|number = 394
|first_author = Dmitrii KOLOTKOV
|second_author = et al.
|publish_date = 16 November 2020
|description = Coronal heating models meet damped slow magnetoacoustic waves
|image=Icon394.png}}

{{Nugget Badge
|title = Self-Consistent Flare Model
|number = 393
|first_author = Wenzhi RUAN
|second_author = and Rony KEPPENS
|publish_date = 2 November 2020
|description = Energy transport by fast particles made self-consistent with MHD flare modeling
|image=Icon393.png}}

{{Nugget Badge
|title = Hot Flare Onsets
|number = 392
|first_author = Hugh HUDSON
|second_author = et al.
|publish_date = 26 October 2020
|description = The initial soft X-ray temperatures of solar flares tend to be in the 10-15 MK range
|image=Icon392.png}}

{{Nugget Badge
|title = Electric Current Neutralization and Eruption
|number = 391
|first_author = Ellis AVALLONE
|second_author = and Xudong SUN
|publish_date = 19 October 2020
|description = Coronal currents without neutralizing return currents appear to
|image=Icon391.png}}

{{Nugget Badge
|title = Prediction of Solar Cycle 25
|number = 390
|first_author = Leif SVALGAARD
|second_author =
|publish_date = 5 October 2020
|description = Now we know how big the next solar maximum will be
|image=Icon390.png}}

{{Nugget Badge
|title = Flare/CME Cartoon Archive
|number = 389
|first_author = Hugh HUDSON
|second_author =
|publish_date = 27 September 2020
|description = A new edition of the Flare/CME archive, nearly a half kilotoon now
|image=Icon389.png}}

{{Nugget Badge
|title = Submerged Flare Acoustic Sources
|number = 388
|first_author = Juan Camilo BUITRAGO CASAS
|second_author = and Angel MARTÍNEZ
|publish_date = 13 September 2020
|description = Flare acoustic radiation emanates from a source _inside_ the Sun
|image=Icon388.png}}

{{Nugget Badge
|title = Circular Ribbon Flare at Microwaves
|number = 387
|first_author = Jeongwoo LEE
|second_author =
|publish_date = 31 August 2020
|description = Breakout reconnection reveals itself via microwave polarization measurements.
|image=Icon387.png}}

{{Nugget Badge
|title = Relation of Non-neutralized electric currents and the activity in active regions
|number = 386
|first_author = P. VEMAREDDY
|second_author =
|publish_date = 24 August 2020
|description = Non-neutralized coronal current systems contribute to CME eruptions
|image=Icon386.png}}

{{Nugget Badge
|title = White-light emission and photospheric magnetic field changes in flares
|number = 385
|first_author = J. Sebastián CASTELLANOS DURÁN
|second_author = and Lucia KLEINT
|publish_date = 17 August 2020
|description = There are strong correlations between white-light flare emissions and line-of-sight magnetic field changes
|image=Icon385.png}}

{{Nugget Badge
|title = Sunspot Differential Rotation in an X-class Flare
|number = 384
|first_author = Richard GRIMES,
|second_author = Balázs PINTÉR and Huw MORGAN
|publish_date = 10 August 2020
|description = Observations suggesting how the coronal tail can wag the photospheric dog
|image=Icon384.png}}

{{Nugget Badge
|title = Energy Partitioning in a Nonthermally Dominated Two-loop Solar Flare
|number = 383
|first_author = Galina MOTORINA
|second_author = et al.
|publish_date = 3 August 2020
|description = Modeling the propagation of energy via GX Simulator in an early-impulsive flare
|image=Icon383.png}}

{{Nugget Badge
|title = SOL2013-11-10 Eruptive Circular-ribbon Flare with Extended Remote Brightenings
|number = 382
|first_author = Chang LIU
|second_author = et al.
|publish_date = 31 July 2020
|description = A circular-ribbon event can launch an eruption by breaking through its separatrix dome
|image=Icon382.png}}

{{Nugget Badge
|title = Extreme-Ultraviolet Late Phase of Solar Flares
|number = 381
|first_author = Rui LIU
|second_author =
|publish_date = 22 June 2020
|description = Both arcade and circular-ribbon flares may sometimes spawn EUV late phase emission
|image=Icon381.png}}

{{Nugget Badge
|title = Energy transport by accelerated particles in the quiet solar atmosphere
|number = 380
|first_author = Lars FROGNER,
|second_author = Boris GUDIKSEN and Helle BAKKE
|publish_date = 15 June 2020
|description = A first study of non-thermal particles integrated into an MHD simulation of the solar atmosphere
|image=Icon380.png}}

{{Nugget Badge
|title = Quasi-periodic pulsations as indicators of oscillatory processes in solar flares
|number = 379
|first_author = Elena KUPRIYANOVA
|second_author = et al.
|publish_date = 11 May 2020
|description = Many, many QPPs
|image=Icon379.png}}

{{Nugget Badge
|title = Rejuvenating Solar Flare Termination Shocks as Particle Accelerators
|number = 378
|first_author = Bin CHEN
|second_author =
|publish_date = 4 May 2020
|description = At last, clear evidence for a long-predicted phenomenon
|image=Icon378.png}}

{{Nugget Badge
|title = Broad symmetrical Doppler-shifted Fe XXI line profiles
|number = 377
|first_author = Vanessa POLITO
|second_author =
|publish_date = 20 April 2020
|description = It is difficult to explain "evaporation" line profiles by superposition of unresolved flows
|image=Icon377.png}}

{{Nugget Badge
|title = Phenomena in the unusually long pre-impulsive phase of SOL2011-06-07
|number = 376
|first_author = Marian KARLICKÝ,
|second_author = Jana KA&Scaron;PAROVÁ, and Robert SYCH
|publish_date = 13 April 2020
|description = A massive and slowly-rising filament eruption reveals important new signatures of the physics
|image=Icon376.png}}

{{Nugget Badge
|title = Evidence for a Coronal Shock Wave Origin for Relativistic Protons Producing Solar Gamma-Rays and Observed by Neutron Monitors at Earth‎
|number = 375
|first_author = Athanasios KOULOUMVAKOS
|second_author = and Gerry SHARE
|publish_date = 6 April 2020
|description = Successful modeling of prolonged solar gamma-ray emissions and terrestrial ground-level cosmic-ray events
|image=Icon375.png}}

{{Nugget Badge
|title = Using overlappogram data to find hot flare plasma
|number = 374
|first_author = Louise HARRA
|
|publish_date = 23 March 2020
|description = Imaging Fe XXIV at high resolution with the EIS slot data
|image=Icon374.png}}

{{Nugget Badge
|title = SOL2017-09-04 (M5.5) 2017 as a Source of Relativistic Electrons and Protons
|number = 373
|first_author = Alexei STRUMINSKII
| (see text)
|publish_date = 16 March 2020
|description = Flare-accelerated particles, rather than SEPs, energize sustained gamma-ray emission
|image=Icon373.png}}

{{Nugget Badge
|title = Heating of the solar photosphere during a white-light flare‎
|number = 372
|first_author = Jan JURČÁK
| (see text)
|publish_date = 2 March 2020
|description = The best-ever spectrum of the flare photosphere
|image=Icon372.png}}

{{Nugget Badge
|title = A Hot Cusp-Shaped Confined Solar Flare
|number = 371
|first_author = Aaron HERNANDEZ-PEREZ
|publish_date = 24 February 2020
|description = A flare may have a prominent hot cusp with the help of any eruption
|image=Icon371.png}}

{{Nugget Badge
|title = The Temporal and Spatial Extension of Gamma-ray Emission from the Sun
|number = 370
|first_author = Nat GOPALSWAMY
|publish_date = 17 February 2020
|description = Sustained solar γ-rays and solar cosmic rays
|image=Icon370.ng.png}}

{{Nugget Badge
|title = A PSP Perihelion
|number = 369
|first_author = Jessie DUNCAN
|second_author = and Hugh Hudson
|publish_date = 20 January 2020
|description = The Parker Solar Probe enters its fourth perihelion already. Now
|image=Icon369.png}}

{{Nugget Badge
|title = Remembering John Brown
|number = 368
|first_author = Alec MacKINNON
|second_author =
|publish_date = 13 January 2020
|description = John passed away unexpectedly on 16 November 2019
|image=Icon368.png}}

{{Nugget Badge
|title = A Global Survey of EUV Coronal Power Spectra
|number = 367
|first_author = Karl Battams
|second_author =
|publish_date = 30 December 2019
|description = Time-series parameter maps of imaged power spectra from an AIA pipeline
|image=Icon367.png}}

{{Nugget Badge
|title = Cosmic Rays over the Rainbow Bridge
|number = 366
|first_author = Hugh Hudson
|second_author = Alec MacKinnon
|publish_date = 16 December 2019
|description = Cosmic rays approach the Sun
|image=Icon366.png}}

{{Nugget Badge
|title = Spectropolarimetric Insight into Plasma-Sheet Dynamics of a Solar Flare
|number = 365
|first_author = Ryan French
|second_author =
|publish_date = 9 December 2019
|description = CoMP polarization patterns in SOL2017-09-10 are amazing
|image=Icon365.png}}

{{Nugget Badge
|title = Lorentz Force Evolution Reveals the Energy Build-up Processes during Recurrent Eruptive Solar Flares‎
|number = 364
|first_author = Ranadeep Sarkar,
|second_author = Nandita Srivastava and Astrid Veronig
|publish_date = 18 November 2019
|description = The net Lorentz force clearly exhibits a build-up and release pattern
|image=Icon364.png}}

{{Nugget Badge
|title = Flare waiting times depend on their magnitudes
|number = 363
|first_author = Hugh Hudson
|second_author =
|publish_date = 11 November 2019
|description = Surprising new evidence for the flare build-up and release process
|image=Icon363.png}}

{{Nugget Badge
|title = Can magnetic reconnection cause solar rainstorms?‎
|number = 362
|first_author = Petra Kohutova
|second_author =
|publish_date = 4 November 2019
|description = Impulsive coronal heating resulting from reconnection can trigger coronal rain
|image=Icon362.png}}

{{Nugget Badge
|title = Non-radial jets on the edges of active regions
|number = 361
|first_author = Peter Wyper
|second_author =
|publish_date = 14 October 2019
|description = The very common jet structures we see can naturally combine twist and breakout
|image=Icon361.png}}

{{Nugget Badge
|title = Searching SOLfully within the Nuggets
|number = 360
|first_author = Hugh Hudson
|second_author =
|publish_date = 7 October 2019
|description = The IAU target identifier works well for finding items about a particular event
|image=Icon360.png}}

{{Nugget Badge
|title = Submillimeter Radiation as the Thermal Component of the Neupert Effect
|number = 359
|first_author = Guillermo Giménez de Castro
|second_author =
|publish_date = 31 September 2019
|description = Flare radiation at the highest frequencies can be bremsstrahlung
|image=Icon359.png}}

{{Nugget Badge
|title = The "Last Best" Flares
|number = 358
|first_author = Hugh Hudson,
|second_author = Ed Cliver, and Brian Dennis
|publish_date = 24 September 2019
|description = Major flares tend to happen at the very ends of sunspot cycles
|image=Icon358.png}}

{{Nugget Badge
|title = Dynamic Processes of the Moreton Wave on 2014 March 29‎
|number = 357
|first_author = Denis Cabezas
|second_author = and the FMT team
|publish_date = 16 September 2019
|description = A beautiful Moreton wave excited by the best-observed flare ever
|image=Icon357.png}}

{{Nugget Badge
|title = EVE-RHESSI DEM Models and the Low-energy Cutoff for Nonthermal Electrons
|number = 356
|first_author = Jim McTiernan
|second_author =
|publish_date = 9 September 2019
|description = Characterizing flare temperature distributions helps to define the non-thermal energy release
|image=Icon356.png}}

{{Nugget Badge
|title = Stealth Coronal Mass Ejections from Active Regions
|number = 355
|first_author = Jennifer O'Kane
|second_author =
|publish_date = 26 August 2019
|description = Perhaps just feeble versions of the same magnetic disease...
|image=Icon355.png}}

{{Nugget Badge
|title = Do Kepler Superflare Stars Really Include Slowly Rotating Sun-like Stars?‎
|number = 354
|first_author = Yuta NOTSU
|second_author =
|publish_date = 15 July 2019
|description = Kepler superflares hint at solar superflares
|image=Icon354.png}}

{{Nugget Badge
|title = Localized Microwave and EUV Bright Structures in an Eruptive Prominence
|number = 353
|first_author = Jing HUANG
|second_author =
|publish_date = 22 June 2019
|description = Detailed correlations between EUV and microwaves in prominence fine structures
|image=Icon353.png}}

{{Nugget Badge
|title = Broken-up hard X-ray spectra found for a loop-top source during a solar limb flare
|number = 352
|first_author = Hao NING,
|second_author = Yao CHEN and Jeongwoo LEE
|publish_date = 16 June 2019
|description = SOL2017-09-10 coronal hard X-ray sources
|image=Icon352.png}}

{{Nugget Badge
|title = The Cosmic-Ray Shadow and Coronal Magnetism
|number = 351
|first_author = Frederik Tenholt
|second_author =
|publish_date = 27 May 2019
|description = The coronal magnetic field measured in Antarctica
|image=Icon351.png}}

{{Nugget Badge
|title = Kristian Birkeland
|number = 350
|first_author = Hugh HUDSON
|second_author = and Lyndsay FLETCHER
|publish_date = 6 May 2019
|description = Space weather a century ago: Kristian Birkeland
|image=Icon350.png}}

{{Nugget Badge
|title = Warm UV loops heated by small-scale cancellation events
|number = 349
|first_author = Seray ŞAHIN
|second_author = and Vasyl YURCHYSHYN
|publish_date = 22 April 2019
|description = Precisely locating the footpoints of warm coronal loops helps identify their source(s) of excitation
|image=Icon349.png}}

{{Nugget Badge
|title = Multiple Regions of Shock-accelerated Particles during a Solar Coronal Mass Ejection
|number = 348
|first_author = Diana MOROSAN
|second_author =
|publish_date = 1 April 2019
|description = LOFAR identifies herringbone sources within the flank of the SOL2017-09-10 shock - no joke
|image=Icon348.png}}

{{Nugget Badge
|title = Persistent Quasi-Periodic Pulsations Detected During the Large X8.2 Solar Flare
|number = 347
|first_author = Laura HAYES
|second_author = and Peter GALLAGHER
|publish_date = 25 March 2019
|description = The most beautiful flare has the most beautiful pulsations
|image=Icon347.png}}

{{Nugget Badge
|title = Is the coronal magnetic field braiding?
|number = 346
|first_author = Markus ASCHWANDEN
|second_author =
|publish_date = 11 March 2019
|description = This iconic cartoon does not relate well to the observations
|image=Icon346.png}}

{{Nugget Badge
|title = An energetic pre-flare: electron distributions in magnetic reconnection outflows
|number = 345
|first_author = Marina BATTAGLIA,
|second_author = Eduard KONTAR and Galina MOTORINA
|publish_date = 18 February 2019
|description = Assessing energy partition in a pre-impulsive flare development
|image=Icon345.png}}

{{Nugget Badge
|title = Linear Polarization in H-alpha Flares
|number = 344
|first_author = Tomoko KAWATE
|second_author = and Yoichiro HANAOKA
|publish_date = 4 February 2019
|description = H-alpha polarization is rarely observable but, in once case, very suggestive
|image=Icon344.png}}

{{Nugget Badge
|title = Short-Period Waves
|number = 343
|first_author = Sijie YU
|second_author = and Bin CHEN
|publish_date = 21 January 2019
|description = New decimetric imaging spectroscopy suggests Alfvénic energy transport in flares
|image=Icon343.png}}

{{Nugget Badge
|title = The Interesting RHESSI/SAS Archive
|number = 342
|first_author = Hugh HUDSON
|second_author = and Martin FIVIAN
|publish_date = 8 January 2019
|description = The full mission database shows RHESSI to have been very stable geometrically
|image=Icon342.png}}

{{Nugget Badge
|title = Homologous White Light Solar Flares‎
|number = 341
|first_author = Paolo ROMANO
|second_author = and Abouazza ELMHAMDI
|publish_date = 31 December 2018
|description = Homologous white-light flares, in rapid succession, and coronal null points
|image=Icon341.png}}

{{Nugget Badge
|title = The flight of FOXSI-3
|number = 340
|first_author = Lindsay GLESENER
|second_author = and Noriyuki NARUKAGE
|publish_date = 10 December 2018
|description = Single-photon counting and direct focusing across hard and soft energies
|image=Icon340.png}}

{{Nugget Badge
|title = Stellar Flares and Starspots
|number = 339
|first_author = Lauren DOYLE
|second_author =
|publish_date = 3 December 2018
|description = Stellar flares don't spatially match their starspots
|image=Icon339.png}}

{{Nugget Badge
|title = Neutron Production in Solar Flares
|number = 338
|first_author = Ron MURPHY
|second_author = and Gerry SHARE
|publish_date = 26 November 2018
|description = Neutron astronomy helps us understand solar flares
|image=Icon338.png}}

{{Nugget Badge
|title = Cycle 25 Strikes Again
|number = 337
|first_author = Kamil BICZ
|second_author =
|publish_date = 20 November 2018
|description = A second, larger Cycle 25 sunspot
|image=Icon337.png}}

{{Nugget Badge
|title = Remembering Marcos Machado via his research
|number = 336
|first_author = Hugh HUDSON
|second_author =
|publish_date = 13 November 2018
|description = Recalling a friend and colleague, and admiring his final paper
|image=Icon336.png}}

{{Nugget Badge
|title = CORONAS/SPIRIT Mg XII and Nanoflares‎
|number = 335
|first_author = Anton REVA
|second_author =
|publish_date = 22 October 2018
|description = Monochromatic Mg XII spectroheliography sets severe limits on nanoflare heating models
|image=Icon335.png}}

{{Nugget Badge
|title = White-light Emission and Non-thermal Electrons‎
|number = 334
|first_author = Kyoung-Sun LEE
|second_author =
|publish_date = 8 October 2018
|description = An intimate relationship between accelerated electrons and visible flare continuum
|image=Icon334.png}}

{{Nugget Badge
|title = Coronal Hard X-ray Sources Revisited
|number = 333
|first_author = Brian DENNIS
|second_author =
|publish_date = 24 September 2018
|description = Reporting some over-interpretation of the evidence for "coronal thick targets"
|image=Icon333.png}}

{{Nugget Badge
|title = Photospheric response to a flare
|number = 332
|first_author = Mike WHEATLAND
|second_author =
|publish_date = 17 September 2018
|description = Sudden changes in the magnetic field in the low atmosphere associated with particle acceleration
|image=Icon332.png}}

{{Nugget Badge
|title = New Views of Global Solar Magnetic Field Evolution Over Four Solar Cycles
|number = 331
|first_author = David WEBB
|second_author =
|publish_date = 27 August 2018
|description = A digital archive of Pat McIntosh's 44 years of solar synoptic observations
|image=Icon331.png}}

{{Nugget Badge
|title = Understanding the co-spatial return current in solar flares
|number = 330
|first_author = Meriem ALAOUI
|second_author = and Gordon HOLMAN
|publish_date = 6 August 2018
|description = Completing the circuit in a thick-target model
|image=Icon330.png}}

{{Nugget Badge
|title = 3D Magnetic Reconnection at a Coronal Null Point
|number = 329
|first_author = Shane MALONEY,
|second_author = Aidan O'Flannagain and Peter Gallagher
|publish_date = 30 July 2018
|description = Large-scale reconnection involved in Type I radio noise storm
|image=Icon329.png}}

{{Nugget Badge
|title = The true dawn of multimessenger astronomy
|number = 328
|first_author = Hugh Hudson
|second_author =
|publish_date = 23 July 2018
|description = Ever since the Carrington flare
|image=Icon328.png}}

{{Nugget Badge
|title = Microwave Imaging Spectroscopy of Flares is Here‎
|number = 327
|first_author = Dale E. Gary,
|second_author = EOVSA and RHESSI Teams
|publish_date = 16 July 2018
|description = Microwave imaging spectroscopy takes a giant leap forward with SOL2017-09-10
|image=Icon327.png}}

{{Nugget Badge
|title = Coronal nanoflares powered by footpoint reconnection
|number = 326
|first_author = Pradeep Chitta,
|second_author = Hardi Peter, and Sami Solanki
|publish_date = 9 July 2018
|description = Coronal nanoflares in active region cores can be powered by the magnetic reconnection in the lower solar atmosphere
|image=Icon326.png}}

{{Nugget Badge
|title = A remarkable, but confused, coronal hard X-ray source
|number = 325
|first_author = Alexandra Lysenko,
|second_author = Larisa Kashapova and Hugh Hudson
|publish_date = 25 June 2018
|description = A remarkable flare in 1999 adds to our short list of extended coronal hard X-ray/microwave sources
|image=Icon325.png}}

{{Nugget Badge
|title = Understanding HMI pseudocontinuum in white-light flares‎
|number = 324
|first_author = Michal &Scaron;vanda
|second_author = et al.
|publish_date = 28 May 2018
|description = The HMI pseudocontinuum (Ic) is ill-calibrated in regions with strong fields, i.e. for white-light flares
|image=Icon324.png}}

{{Nugget Badge
|title = To beam or not to beam - that is (still) the question
|number = 323
|first_author = Paulo Simões
|second_author = and Hugh Hudson
|publish_date = 14 May 2018
|description = Descriptions of the lower solar atmosphere of flares ca. Cycle 21 sound surprisingly current
|image=Icon323.png}}

{{Nugget Badge
|title = Observation of Cosmic Ray Spallation Events from SoHO‎
|number = 322
|first_author = Serge Koutchmy
|second_author = and Ehsan Tavabi
|publish_date = 7 May 2018
|description = LASCO's images capture high-energy nuclear interactions from cosmic-ray hits
|image=Icon322.png}}

{{Nugget Badge
|title = A Sunspot from Cycle 25 for sure
|number = 321
|first_author = Tomek Mrozek
|second_author = and Hugh Hudson
|publish_date = 10 April 2018
|description = YES! Cycle 25 is here!
|image=Icon321.png}}

{{Nugget Badge
|title = Blue-wing enhancement of the Mg II h and k lines in a flare
|number = 320
|first_author = Akiko TEI
|second_author =
|publish_date = 9 April 2018
|description = Flare loops involve a cool upflow preceding the hot evaporation flow
|image=Icon320.png}}

{{Nugget Badge
|title = NuSTAR detects X-ray flares in the quiet Sun
|number = 319
|first_author = Matej Kuhar
|second_author = and Säm Krucker
|publish_date = 26 March 2018
|description = Quiet-Sun flares may not be powerful, but they look a lot like ordinary flares
|image=Icon319.png}}

{{Nugget Badge
|title = Homologous CME/flares from AR 12371
|number = 318
|first_author = Panditi Vemareddy
|second_author = and Pascal Demoulín
|publish_date = 19 March 2018
|description = An excellent set of homologous flare/CMEs analyzed and explained
|image=Icon318.png}}

{{Nugget Badge
|title = Non-Maxwellian Diagnostics from SDO/EVE Spectra of an X-class Flare
|number = 317
|first_author = Elena Dzifčáková
|second_author = and Jaroslav Dudík
|publish_date = 16 February 2018
|description = Ratios of high-excitation ions can readily detect κ-distributions in flare plasmas
|image=Icon317.png}}

{{Nugget Badge
|title = Joint MinXSS and RHESSI Flare X-ray Spectra between 1 and 15 keV
|number = 316
|first_author = Chris Moore, Brian Dennis and the MinXSS Science Team
|publish_date = 5 February 2018
|description = MinXSS adds systematic views of flare soft X-ray spectra to RHESSI imagery
|image=Icon316.png}}

{{Nugget Badge
|title = Parameterized Flare Models with Chromospheric Compressions
|number = 315
|first_author = Adam Kowalski & Joel Allred
|publish_date = 17 January 2018
|description = A new approach to modeling the lower flare atmosphere
|image=FlareModelsKowalskiAllred.png}}

{{Nugget Badge
|title = A Curious Sunspot Group in 2018
|number = 314
|first_author = Hugh Hudson
|publish_date = 14 January 2018
|description = The first new sunspot group of 2018 emerged at the wrong latitude
|image = Icon314.png}}

{{Nugget Badge
|title = Tecumseh's Eclipse and Astrophysics
|number = 313
|first_author = Hugh Hudson
|publish_date = 25 December 2017
|description = The solar corona was first recognized as such, and named, in an eclipse of 1806
|image = Icon313.png}}

{{Nugget Badge
|title = Hunting for Hidden Tiny Flares
|number = 312
|first_author = Shin-nosuke ISHIKAWA
|publish_date = 27 November 2017
|description = FOXSI-2 says that episodic energy releases are still viable as a part of the coronal heating problem.
|image = Icon312.png}}

{{Nugget Badge
|title = Unusual Type III Burst Dynamics Produced by Diverging Magnetic Fields
|number = 311
|first_author = Patrick McCauley
|publish_date = 20 November 2017
|description = Unusual type III bursts follow coronal separatrix structures.
|image = Icon311.png}}

{{Nugget Badge
|title = Valderrama in the 21st Century
|number = 310
|first_author = Hugh Hudson
|publish_date = 31 October 2017
|description = A newly-described white-light flare from the 19th century!..
|image = Icon310.png}}

{{Nugget Badge
|title = Electron Scattering in the Flaring Corona
|number = 309
|first_author = Sophie Musset
|publish_date = 24 October 2017
|description = Diffusive transport may contribute to the trapping of electrons in coronal X-ray sources
|image = Icon309.png}}

{{Nugget Badge
|title = The Power of Turbulence
|number = 308
|first_author = Nic Bian
|publish_date = 25 September 2017
|description = Turbulent energy content may underlie flare energy transfer, magnetic reconnection, and particle acceleration
|image = Icon308.png}}

{{Nugget Badge
|title = The Kelvin Force and Loop-Top Concentration
|number = 307
|first_author = Kiyoto SHIBASAKI
|publish_date = 18 September 2017
|description = New physics can explain the perplexing overpressure at the flare looptop regions
|image = Icon307.png}}

{{Nugget Badge
|title = The Last Best Flare of Cycle 24?
|number = 306
|first_author = Säm Krucker
|second_author = and Hugh Hudson
|publish_date = 11 September 2017
|description = Right on schedule, Cycle 24 has produced a great flare (with a GLE)
|image = Icon306.png}}

{{Nugget Badge
|title = Electric Current Neutralization and Solar Eruption in Active Regions
|number = 305
|first_author = Yang LIU
|second_author =
|publish_date = 28 August 2017
|description = Active current systems in the solar corona don't have return currents
|image = Icon305.png}}

{{Nugget Badge
|title = RHESSI and the Megamovie
|number = 304
|first_author = Hugh Hudson, Laura Peticolas,
|second_author = and Juan Carlos Martínez Oliveros
|publish_date = 31 July 2017
|description = A wholly new way to view a solar eclipse, and to do solar astrometry
|image = Icon304.png}}

{{Nugget Badge
|title = Bastille Day 2017
|number = 303
|first_author = Hugh Hudson
|second_author = and Säm Krucker
|publish_date = 24 July 2017
|description = Interesting flares really do happen on Bastille Day...
|image = Icon303.png}}

{{Nugget Badge
|title = The Solar X-ray Limb III
|number = 302
|first_author = Marina Battaglia
|second_author = and Gordon Hurford
|publish_date = 12 June 2017
|description = RHESSI succeeds with a wholly new way to measure the solar diameter
|image = Icon302.png}}

{{Nugget Badge
|title = Double Coronal X-ray and Microwave Sources Associated With A Magnetic Breakout Solar Eruption
|number = 301
|first_author = Yao CHEN
|second_author =
|publish_date = 29 May 2017
|description = A different explanation of the double coronal hard X-ray sources
|image = Icon301.png}}

{{Nugget Badge
|title = A Lasso Model for Solar Gamma-ray Events
|number = 300
|first_author = Hugh Hudson
|second_author =
|publish_date = 15 May 2017
|description = A toy model hoping to explain the SEP/LAT relationship
|image = Icon300.png}}

[[RHESSI Science Nuggets 200 to 299|Next Nuggets]]

File:Icon526.png

2026-05-20T06:41:41Z

Hhudson: Hhudson uploaded a new version of File:Icon526.png

X-ray Log Letters

2026-05-19T10:53:53Z

Hhudson: Janusz's better figure

{{Infobox Nugget |name = Nugget
|title = X-ray Log Letters
|number = 526
|first_author = Hugh HUDSON and
|second_author = Ed CLIVER
|publish_date = May 18, 2026
|next_nugget = TBD
|previous_nugget = {{#ask: [[Category:Nugget]] [[RHESSI Nugget Index::525]]}}
}}

== Introduction ==

As all students of solar activity know, the
[https://www.stce.be/educational/classification naming scheme]
for solar flares involves the letters ABCMX.
These date from the dawn of the space age, when the first
[https://en.wikipedia.org/wiki/SOLRAD SOLRAD] satellites began to monitor
solar X-ray emission.
Flares of a wide range of brightnesses were immediately apparent, and
[https://www.noaa.gov NOAA]
ionospheric physicist Don Baker (Ref. [1]) came up with a classification
that matched decades of peak flux to letters: Cnn would mean nn x 10-4,
and the basic flux level 1.0 x 10-6 W/m2 would be class C1.0.
Initially it was just CMX ("Common", "Medium", "Extreme")
Each flare has a peak flux in the standard 1-8 Å band,
and the range of magnitudes of flare peak fluxes is so great that it's most
convenient to record the
[https://en.wikipedia.org/wiki/Common_logarithm logarithm] of the
flux.
This convention moved directly into the
[https://www.swpc.noaa.gov/products/goes-x-ray-flux GOES]
satellite era, and from 1974 the standardized flux measurements
have come from this series of spacecraft (Ref. [2]).

In standard units a C-class flare has a peak flux greater than 10-7
W/m2, with M-class and X-class greater by powers of 10.
Conventionally a flare 10% brighter than the threshold, with peak flux
1.1 x 10-7 W/m2, would then become a C1.1 flare.
The letter thus represents the truncated logarithm of the peak flux.
The magnitudes are not rounded off and represent the solar X-ray flux
conventionally in a 1-min integration interval.
A background quiescent solar emission level is not subtracted; these routine
observations show the total solar X-ray flux in "Sun-as-a-star" mode.
Weaker events near the background level, which can indeed exceed C1 during
active times, will thus not be quite as energetic as their name implies.

Low background solar X-ray fluxes during solar minima allowed the GOES
detector technology to detect fainter events, and so two new decades were
added to the letter string: A and B, with no particular descriptive
interpretation.
Thus we arrived at the current letter string ABCMX.

== The SphinX breakthrough (to the bottom) ==

The first routine flare monitoring with sufficient sensitivity to
detect the solar quiescent X-ray flux appeared with the SphinX
instrument from the
[https://scholar.google.com/citations?user=vDLMZPIAAAAJ&hl=pl Sylwester]
group at Wroc&lstrok;aw (Ref. [3]).
For 1-8 Å this turned out to be about two decades below the A level.
Hence, two more letters: Q "quiet" and S "small", leading to the more complete
string QSABCMX.
Figure 1 shows SphinX data from the 2009
[https://en.wikipedia.org/wiki/Solar_cycle solar minimum].

[[File:526f1.png|center|thumb|600px|caption|Figure 1: 
SphinX observations from solar minimum 2009, showing microflares down to the Q level
(as indicated by vertical blue lines at the bottom).
The regions marked with red show times of SphinX minimum counting rate, at levels far
below the original CMX range (Ref. [3]).
Green regions contain microflare excesses.
Excesses above this level are due to weak flares and quiescent active regions.
Translated to the GOES calibration, the weakest events are measured in units of
10-10 W/m2.
]]

== The greatest events (to the top) ==

At the top end of the GOES soft X-ray distribution, a handful of the most
extreme events had saturated the GOES 1-8 Å readout.
Ref. [4] describes an evenhanded patching of these items, together with a
correction for a systematic offset (Ref. [2]).
This produced a list of 37 >X10 events after background subtraction.
This basic manipulation departs from tradition, and so we provide this
[greatest flares]
catalog using the letter system "QSabcmxyz".
To translate, the new "y" class is the old "X10" class, sometimes now called
"S" (Ref. 5]), and the new catalog lists 37 of them.
The new "z" class has no examples yet (but we're hopeful), although the
[https://heliowiki.smce.nasa.gov/wiki/index.php/The_1859_Space_Weather_Event_Revisited Carrington event]
might have been in that category.

A sample of the newly lettered catalog is here, representing a signal-to-background requirement of 1 (flare
doubles the preflare level), resulting in a reduction of total number from 48,131 to 42,469 for the timespan
1974-2023.
The new letter string is QSabcmxyz, pleasingly symmetric.
SOL1984-02-10T22:47 C9.1 m1.21
SOL1984-02-11T01:31 C3.7 c3.78
SOL1984-02-11T02:45 M2.9 m4.07
SOL1984-02-11T03:44 C2.0 c1.93
SOL1984-02-11T04:33 C2.1 c1.78
SOL1984-02-11T04:56 C2.1 c2.23
SOL1984-02-11T09:06 C2.6 c2.46
SOL1984-02-11T10:09 C1.8 c1.43
SOL1984-02-11T12:16 C3.0 c3.19
SOL1984-02-11T14:24 C4.8 c6.03
The catalog contains 37 y-class events (previously X10 or S), but no z-class examples because the Sun refuses to
cooperate. At the C->c level, many events get downgraded because of background subtraction, but the systematic
historical scale adjustment described in Ref. [2] tends to compensate for that.

== Conclusions ==

See the [https://www.astro.gla.ac.uk/users/hsh3f/QSabcmxyz.html further discussion] of how QSabcmxyz works, or to access it directly click [https://www.astro.gla.ac.uk/users/hsh3f/QSabcmxyz.txt here] for a 2-MB text listing.

== References ==

[1] "Sentinels of the sun: forecasting space weather," B. Poppe and K. Jorden, 2006

[2] [https://www.sciencedirect.com/science/article/pii/B9780128143278000196 "GOES-R Series Solar X-ray and Ultraviolet Irradiance"]

[3] [https://doi.org/10.1007/s11207-019-1565-9 "Analysis of Quiescent Corona X-ray Spectra from SphinX During the 2009 Solar Minimum"]

[4] [https://ui.adsabs.harvard.edu/abs/2024SoPh..299...39H "The Greatest GOES Soft X-ray Flares"]

[5] [https://ui.adsabs.harvard.edu/abs/2025ApJ...979L..16T "The Occurrence of Powerful Flares Stronger than X10 Class in Solar Cycles"]

File:526f1.png

2026-05-19T10:45:21Z

Hhudson: Hhudson uploaded a new version of File:526f1.png

SolarNuggets

2026-05-14T10:50:24Z

Hhudson:

Welcome to the [[SolarNuggets]] collection, which extends the series of [[RHESSI]] Nuggets. The following is a time-ordered list of the latest Nuggets added to the HelioWiki. An [[:Category:Nugget|alphabetical list of the SolarNuggets]] is also available as well as [[:Category:RHESSI Nugget List|yearly lists]]. One can search on author, topic, IAU flare identifier, etc.). We welcome volunteer authors - please see our page of [[Help:For_Authors| help for authors]] or just send an email to the Curator at (hugh.hudson@glasgow.ac.uk).

{{Nugget Badge
|title = X-ray Log Letters‎‎
|number = 526
|first_author = Hugh HUDSON
|second_author = and Ed CLIVER
||publish_date = 18 May 2026
|description = Replacing ABCMX with a new comprehensive and quantitative QSabcmxyz catalog
|image=Icon526.png}}

{{Nugget Badge
|title = How Extreme Can Solar Flares Get? A Statistical View‎‎
|number = 525
|first_author = Lapo Ceccarelli
|second_author = and Daniela CASTRO-CAMILO
||publish_date = 4 May 2026
|description = A proper statistical treatment of the prospects for an extreme solar flare event
|image=Icon525.png}}

{{Nugget Badge
|title = Observations of Slow Elemental Abundance Decay in Association to CME
|number = 524
|first_author = Saara TAKALA
||publish_date = 27 April 2026
|description = Soft X-ray spectroscopy tracks coronal abundance variations associated with a CME
|image=Icon524.png}}

{{Nugget Badge
|title = An Unusual Long-Lived Radio Burst Oscillating in Frequency
|number = 523
|first_author = Marian KARLICKÝ,
|second_author = Robert SYCH and Alena ZEMANOVÁ
||publish_date = 20 April 2026
|description = Remarkable decimetric signatures of structured outflows from a flaring active region
|image=Icon523.png}}

{{Nugget Badge
|title = Lateral Deformation of Large-scale Coronal Mass Ejections during the Transition from Nonradial to Radial Propagation
|number = 522
|first_author = Huidong HU
||publish_date = 13 April 2026
|description = Coronal mass ejections can begin their trajectory highly tilted to the vertical, but then straighten out
|image=Icon522.png}}

{{Nugget Badge
|title = Can EUV Power-Spectral Indices Reveal Imminent Solar Flares?
|number = 521
|first_author = Sihui ZHONG,
|second_author = Dmitrii KOLOTKOV and Valery M. NAKARIAKOV
||publish_date = 6 April 2026
|description = A new flare-precursor observable - power spectra
|image=Icon521.png}}

{{Nugget Badge
|title = How energetic can solar flares become?
|number = 520
|first_author = Natalie KRIVOVA
||publish_date = 31 March 2026
|description = The history of active-region areas suggests the possibility of solar superflares
|image=Icon520.png}}

{{Nugget Badge
|title = Hinode EIS Observations of Plasma Composition Evolution and Radiative Cooling of Flare Loops
|number = 519
|first_author = Teodora MIHĂILESCU,
|second_author = Peter YOUNG et AL.
||publish_date = 16 March 2026
|description = Higher FIP bias than expected in some flare loops, a diagnostically interesting result
|image=Icon519.png}}

{{Nugget Badge
|title = When Magnetic Field Lines Stretch, Snap, and Expand: A New Look at Solar Flares with L-maps
|number = 518
|first_author = Maria KAZACHENKO,
|second_author = Yuhong FAN and Andrey AFANASYEV
||publish_date = 9 March 2026
|description = A clever new tool tracks magnetic connectivity (and energy) during flare/CME occurrence
|image=Icon518.png}}

{{Nugget Badge
|title = Observational Evidence Linking Loop Length and Thermal/Nonthermal Peak Timing in Solar Flares
|number = 517
|first_author = Solomon PERRIYIL
||publish_date = 23 February 2026
|description = Clear evidence for the universality of the physics behind the Neupert Effect
|image=Icon517.png}}

{{Nugget Badge
|title = A fine-scale bright kernel captured by Hi-C 3 in the post-maximum phase of an M-class solar flare
|number = 516
|first_author = Sanjiv TIWARI
||publish_date = 9 February 2026
|description = The Hi-C rocket catches an extremely compact brightening in late-phase flare ribbon development
|image=Icon516.png}}

{{Nugget Badge
|title = On the Relationship Between Nanoflare Energy and Delay in the Closed Solar Corona
|number = 515
|first_author = Shanwlee SOW MONDAL et al.
||publish_date = 19 January 2026
|description = Nanoflaring implies energy storage and sudden release, suggesting correlation between event energy and its timing
|image=Icon515.png}}

{{Nugget Badge
|title = Fine structures in solar flare ribbons
|number = 514
|first_author = Jonas THOEN FABER
||publish_date = 12 January 2026
|description = Elongated "riblets" commonly rise out of flare ribbons, and have characteristic Doppler shifts
|image=Icon514.png}}

{{Nugget Badge
|title = The M- and X-class White-light Flares in Super Active Region NOAA 13664/13697
|number = 513
|first_author = Zhichen JING
|second_author = and Ying LI
|publish_date = 5 January 2026
|description = "Super" active regions have relatively more frequent X-class flares, which correlate well with visible continuum (white-light flare) emission
|image=Icon513.png}}

{{Nugget Badge
|title = Iron Fluorescence in X-class Solar Flares
|number = 512
|first_author = Abhilash SARWADE
|publish_date = 8 December 2025
|description = A new spectroscopic capability for Iron K-alpha fluorescence
|image=Icon512.png}}

{{Nugget Badge
|title = Sun-as-a-star Analysis of a Solar Eruption Source Region Using H-alpha Spectroscopic Observations from CHASE
|number = 510
|first_author = Xiaofeng LIU
|second_author = and Yijun HOU
|publish_date = 24 November 2025
|description = Sun-as-a-star observations help to translate solar/stellar processes
|image=Icon5010.png}}

{{Nugget Badge
|title = On the Origin of Solar Long-Duration Gamma-Ray Flares‎‎‎‎
|number = 509
|first_author = Alessandro BRUNO
|publish_date = 3 November 2025
|description = Do we really need a CME to produce a long-duration solar gamma-ray event?
|image=Icon509.png}}

{{Nugget Badge
|title = FAI and GOES eclipses‎‎
|number = 508
|first_author = Hugh HUDSON
|publish_date = 20 October 2025
|description = Flare anticipation via FAI may have problems during GOES eclipses, which are really interesting in their own right
|image=Icon508.png}}

{{Nugget Badge
|title = The EUV Late Phase‎
|number = 507
|first_author = Sascha ORNIG
|publish_date = 13 October 2025
|description = Basic comparative statistics of the ELP, a distinct flare phenomenon
|image=Icon507.png}}

{{Nugget Badge
|title = Time evolution of flare-accelerated electrons using the warm-target model‎
|number = 506
|first_author = Debesh BHATTACHARJEE
|publish_date = 6 October 2025
|description = Considering a "warm" thick target allows flare-accelerated electrons to be treated self-consistently
|image=Icon506.png}}

{{Nugget Badge
|title = SOLSTICE observes flare Doppler shifts in Si III
|number = 505
|first_author = Luke MAJURY
|publish_date = 30 September 2025
|description = A rarely used database suggests prograde-flow Doppler shifts in flaring plasmas
|image=Icon505.png}}

{{Nugget Badge
|title = Flare Phases and the Earth's Ionospheric Response
|number = 504
|first_author = Susanna BEKKER
|publish_date = 16 September 2025
|description = A flare's "EUV late phase" is surprisingly geoeffective
|image=Icon504.png}}

{{Nugget Badge
|title = Neupertianity
|number = 503
|first_author = Hugh HUDSON
|publish_date = 25 August 2025
|description = It's hard to avoid the Neupert Effect
|image=Icon503.png}}

{{Nugget Badge
|title = Synchrotron Radiation and the Foundations for a Cosmic Bridge
|number = 502
|first_author = Immanuel JEBARAJ
|publish_date = 11 August 2025
|description = Gyrosynchrotron radiation in shocks: a cosmic connection
|image=Icon502.png}}

{{Nugget Badge
|title = The Aulanier Effect: drifting footpoints of CME flux ropes
|number = 501
|first_author = Jaroslav DUDÍK,
|second_author = Juraj LÖRINČÍK and Brigitte SCHMIEDER
|publish_date = 21 July 2025
|description = The breakthrough to 3D flare physics: the Aulanier Effect
|image=Icon501.png}}

{{Nugget Badge
|title = Five Hundred Nuggets
|number = 500
|first_author = Hugh HUDSON
|publish_date = 14 July 2025
|description = A milestone
|image=Icon169.png}}

{{Nugget Badge
|title = Quasiperiodic Pulsations in the Balmer Continuum in an X-class Solar White-light Flare
|number = 499
|first_author = De-Chao SONG et al.
|publish_date = 30 June 2025
|description = QPP in the Balmer continuum: the powerful heartbeat of a flare
|image=Icon499.png}}

{{Nugget Badge
|title = High-Resolution Observations of a C3 class White-Light Flare
|number = 498
|first_author = Zhe XU and
|second_author = Xiaoli YAN
|publish_date = 16 June 2025
|description = A compact white-light flare with vortical motions (and hard X-rays)
|image=Icon498.png}}

{{Nugget Badge
|title = The Sun's open-closed flux boundary and the origin of the slow solar wind
|number = 497
|first_author = Chloe WILKINS and
|second_author = David PONTIN
|publish_date = 26 May 2025
|description = Identifying the solar sources of slow solar wind
|image=Icon497.png}}

{{Nugget Badge
|title = Delay of Near-Relativistic Electrons
|number = 496
|first_author = Grant MITCHELL
|publish_date = 19 May 2025
|description = Parker Solar Probe solves an old mystery about type III bursts
|image=Icon496.png}}

{{Nugget Badge
|title = A Multi-Site Telescope for Multi-Height for Synoptic Observations
|number = 495
|first_author = Fallon KONOW
|publish_date = 11 May 2025
|description = A new synoptic network for observations at multiple wavelengths
|image=Icon495.png}}

{{Nugget Badge
|title = On turbulent magnetic reconnection: fast and slow mean steady-states
|number = 494
|first_author = Sage STANISH
|second_author = and David MacTAGGART
|publish_date = 28 April 2025
|description = In a turbulent medium, magnetic reconnection has two limiting domains
|image=Icon494.png}}

{{Nugget Badge
|title = Quasi-Periodic Pulsations in Ionospheric TEC and Flare EUV
|number = 493
|first_author = Aisling O'HARE
|publish_date = 21 April 2025
|description = The Earth's ionosphere reflects QPPs, with a small delay
|image=Icon493.png}}

{{Nugget Badge
|title = Metis observations of Alfvenic outflows driven by interchange reconnection in a pseudostreamer
|number = 492
|first_author = Paolo ROMANO and the Metis team
|publish_date = 7 April 2025
|description = Exactly as predicted by numerical simulations... a rare coup
|image=Icon492.png}}

{{Nugget Badge
|title = Solar Rollercoaster: looping-the-loop in the solar corona
|number = 491
|first_author = Mohamed NEDAL et al.
|publish_date = 31 March 2025
|description = Large-scale helical motion in the flare/CME SOL2024-05-14
|image=Icon491.png}}

{{Nugget Badge
|title = Proton Beam Energy Deposition as a Mechanism of Deep Photospheric Heating
|number = 490
|first_author = Samuel GRANOVSKY
|second_author = and Alexander KOSOVICHEV
|publish_date = 17 March 2025
|description = Evidence for proton beams in white-light flares
|image=Icon490.png}}

{{Nugget Badge
|title = New insights into the proton precipitation sites in solar flares
|number = 489
|first_author = Andrea Francesco BATTAGLIA
|second_author = and Säm KRUCKER
|publish_date = 17 February 2025
|description = There is no detectable difference in proton and electron foopoint locations after all
|image=Icon489.png}}

{{Nugget Badge
|title = Solar Gamma-Ray Evidence for a Distinct Population of MeV Flare-Accelerated Electrons
|number = 488
|first_author = Gerry SHARE
|second_author =
|publish_date = 10 February 2025
|description = Relativistic electrons in solar flares newly recognized as a distinct process
|image=Icon488.png}}

{{Nugget Badge
|title = From Chromospheric Evaporation to Coronal Rain: An Investigation of the Mass and Energy Cycle of a Flare‎
|number = 487
|first_author = Seray &Scedil;AHIN
|second_author = and Patrick ANTOLIN
|publish_date = 3 February 2025
|description = A first quantitative comparison of flare evaporation and coronal rain
|image=Icon487.png}}

{{Nugget Badge
|title = Energetic neutral atoms detected in the large solar energetic particle event of February 2022‎
|number = 486
|first_author = Christina COHEN
|second_author =
|publish_date = 20 January 2025
|description = Only the second direct observation of high-energy neutral atoms from the Sun
|image=Icon486.png}}

{{Nugget Badge
|title = Magnetic topology of quiet-Sun Ellerman bombs and associated ultraviolet brightenings‎
|number = 485
|first_author = Aditi BHATNAGAR
|second_author =
|publish_date = 6 January 2025
|description = Tiny "Ellerman Bombs" occur all across the solar surface, with differences
|image=Icon485.png}}

{{Nugget Badge
|title = Unveiling CME Dynamics: Rare Rotations of CMEs in the Heliosphere
|number = 484
|first_author = Sandeep KUMAR and
|second_author = Nandita SRIVASTAVA
|publish_date = 30 December 2024
|description = CMEs usually do not show additional rotation as they move though the heliosphere
|image=Icon484.png}}

{{Nugget Badge
|title = Spatial and Spectral Evolution of Microwave and X-Ray Sources During the Limb Flare SOL2023-02-05
|number = 483
|first_author = Yulia N. SHAMSUTDINOVA
|publish_date = 23 December 2024
|description = Rare microwave imaging spectroscopy of a hot-onset precursor event
|image=Icon483.png}}

{{Nugget Badge
|title = High-resolution observational analysis of flare ribbon fine structures
|number = 482
|first_author = Jonas THOEN FABER
|publish_date = 16 December 2024
|description = Spatially periodic fine structures in flare ribbons reveal current-sheet tearing
|image=Icon482.png}}

{{Nugget Badge
|title = Advection and super-diffusive expansion as the model of flare accelerated electron transport in type III solar radio bursts
|number = 481
|first_author = Eduard KONTAR
|publish_date = 9 December 2024
|description = Sturrock's dilemma resolved
|image=Icon481.png}}

{{Nugget Badge
|title = Faraday's Law in Solar Flares: A Cautionary Message
|number = 480
|first_author = Michael FARADAY
|publish_date = 2 December 2024
|description = We must not forget the global implications of Faraday's Law
|image=Icon480.png}}

{{Nugget Badge
|title = Remarkable NUV Spectrum of an M-star Megaflare
|number = 479
|first_author = Adam KOWALSKI
|publish_date = 25 November 2024
|description = Remarkable NUV spectra from an HST stellar flare
|image=Icon479.png}}

{{Nugget Badge
|title = Revised Point-Spread Functions of AIA and their effect on DEM analyses
|number = 478
|first_author =Stefan HOFMEISTER,
|second_author = Daniel Wolf SAVIN, and Michael HAHN
|publish_date = 18 November 2024
|description = Substantial revisions of the AIA point-response functions
|image=Icon478.png}}

{{Nugget Badge
|title = How much of the energy in flare-accelerated electrons reaches the chromosphere?
|number = 477
|first_author = Meriem ALAOUI
|second_author = and Gordon HOLMAN
|publish_date = 11 November 2024
|description = Keeping flare-accelerated electrons out of the chromosphere
|image=Icon477.png}}

{{Nugget Badge
|title = Spatially resolved plasma composition evolution in a solar flare
|number = 476
|first_author = Andy S. H. TO
|publish_date = 4 November 2024
|description = Reconnection outflow feeds abundance variations
|image=Icon476.png}}

{{Nugget Badge
|title = HOPE during high activity
|number = 475
|first_author = Hugh HUDSON
|second_author = and Alphonse STERLING
|publish_date = 28 October 2024
|description = Hot onsets appear even in the most active solar conditions
|image=Icon475.png}}

{{Nugget Badge
|title = Simulated heliospheric electron spectra show sensitivity to plasma properties of a source region in the flaring corona
|number = 474
|first_author = Ross PALLISTER
|second_author = and Natasha JEFFREY
|publish_date = 21 October 2024
|description = Getting closer to an understanding of how solar energetic particles "escape"
|image=Icon474.png}}

{{Nugget Badge
|title = An extremely complex active region with very strong non-neutralized electric currents
|number = 473
|first_author = Ioannis KONTOGIANNIS
|publish_date = 14 October 2024
|description = Large non-neutralized electric currents flow through the active-region corona
|image=Icon473.png}}

{{Nugget Badge
|title = An X9 flare and its huge crochet (SFE)
|number = 472
|first_author = Hugh HUDSON
|publish_date = 7 October 2024
|description = The geomagnetic effect (SFE/crochet) that will calibrate the Carrington flare
|image=Icon472.png}}

{{Nugget Badge
|title = All microflares that accelerate electrons to high energies are rooted in sunspots
|number = 471
|first_author = Andrea Francesco BATTAGLIA
|publish_date = 30 September 2024
|description = Microflares with hard X-ray spectra are a well-defined class, and invariably have one footpoint embedded in a sunspot
|image=Icon471.png}}

{{Nugget Badge
|title = The warm-target model and kappa distributions
|number = 470
|first_author = Yingjie LUO
|publish_date = 16 September 2024
|description = A self-consistent treatment of non-thermal electron spectra points to kappa distributions
|image=Icon470.png}}

{{Nugget Badge
|title = Is there HOPE for Hyder flares...
|number = 468
|first_author = Hugh HUDSON
|publish_date = 15 March 2024
|description = Filament eruptions/Hyder flares/disparitions brusques may all show HOPE
|image=Icon468.png}}

{{Nugget Badge
|title = Sun-as-a-star Analysis of the M8.7 Flare on 2022 October 2 Using H-alpha and EUV Spectra Taken by SMART/SDDI and SDO/EVE
|number = 467
|first_author = Takato OTSU
|publish_date = 19 February 2024
|description = Whole-Sun spectroscopic observations can readily detect ejecta
|image=Icon467.png}}

{{Nugget Badge
|title = Unexpected Asymmetry in GeV Emission
|number = 466
|first_author = Bruno ARSIOLI and Elena ORLANDO
|publish_date = 15 January 2024
|description = The high-energy solar gamma radiation shows inexplicable but fascinating properties
|image=Icon466.png}}

{{Nugget Badge
|title = When it rippled in one place and exploded in another
|number = 465
|first_author = Ivan ZIMOVETS
|publish_date = 25 December 2023
|description = Pulsations precede a flare, but seem unrelated
|image=Icon465.png}}

{{Nugget Badge
|title = Solar flares: evaporation and simulation‎
|number = 464
|first_author = Malcolm DRUETT
|publish_date = 18 December 2023
|description = Fitting beam electrons into multi-dimensional models
|image=Icon464.png}}

{{Nugget Badge
|title = Pre-impulsive and Impulsive Phases of the March 28, 2022 Sub-Terahertz Flare
|number = 463
|first_author = Galina G. MOTORINA
|publish_date = 11 December 2023
|description = A flare with an increasing sub-THz spectrum and sub-THZ precursor information
|image=Icon463.png}}

{{Nugget Badge
|title = Coronal Bright Points
|number = 462
|first_author = Daniel NÓBREGA-SIVERIO
|publish_date = 27 November 2023
|description = Bright EUV rowel-like structures can result from null-point reconnection
|image=Icon462.png}}

{{Nugget Badge
|title = Aurora-like Radio Emission from a Sunspot
|number = 461
|first_author = Sijie YU
|publish_date = 20 November 2023
|description = Maser action above a sunspot
|image=Icon461.png}}

{{Nugget Badge
|title = Search for a Flare Anticipation Index (FAI)
|number = 460
|first_author = Hugh HUDSON
|second_author = and Jim McTiernan
|publish_date = 13 November 2023
|description = Quantifying flare precursors on a few-minute time scale
|image=Icon460.png}}

{{Nugget Badge
|title = Bouncing motions of fast electrons using Nobeyama Radioheliograph
|number = 459
|first_author = Keitarou MATSUMOTO
|publish_date = 6 November 2023
|description = Solar evidence for conservation of second adiabatic invariant in particle motion
|image=Icon459.png}}

{{Nugget Badge
|title = Impact of nanoflare heating in the lower solar atmosphere
|number = 458
|first_author = Helle BAKKE
|publish_date = 30 October 2023
|description = The behavior of nanoflare fast electrons in Bifrost models
|image=Icon458.png}}

{{Nugget Badge
|title = Precise timing of flare footpoint sources from mid-infrared observations‎
|number = 457
|first_author = Paulo SIMÕES et al.
|publish_date = 23 October 2023
|description = Mid-IR observations at high spatial and high temporal resolution: Conjugacy
|image=Icon457.png}}

{{Nugget Badge
|title = The Greatest GOES Flares‎
|number = 456
|first_author = Hugh HUDSON
|second_author = and Ed CLIVER
|publish_date = 25 September 2023
|description = The greatest GOES events, re-analyzed, fall short of expectations
|image=Icon456.png}}

{{Nugget Badge
|title = Introducing SunSketcher
|number = 455
|first_author = Hugh HUDSON
|second_author = and Gordon EMSLIE
|publish_date = 11 September 2023
|description = Galloping towards roundup in the 2024 total solar eclipse
|image=Icon455.png}}

{{Nugget Badge
|title = TeV Gamma rays from the Quiescent Sun
|number = 454
|first_author = Mehr Un NISA
|second_author = and John BEACOM
|publish_date = 21 August 2023
|description = Solar photons at unprecedented high energies
|image=Icon454.png}}

{{Nugget Badge
|title = Temporal and Spatial Characteristics of Hard X-Ray Sources in Flare Model with Vertical Current Sheet
|number = 453
|first_author = Alexander SHABALIN, Eugenia OVCHINNIKOVA,
|second_author = and Yuri CHARIKOV
|publish_date = 7 August 2023
|description = Modeling betatron acceleration in current-sheet development.
|image=Icon453.png}}

{{Nugget Badge
|title = Spatial Distribution of Magnetic Reconnection Rate in an M6.5 Solar Flare
|number = 452
|first_author = Ju JING
|publish_date = 12 June 2023
|description = Linking hard X-rays to high-resolution images that show reconnection rates.
|image=Icon452.png}}

{{Nugget Badge
|title = Statistical study of Type III bursts and associated HXR emissions
|number = 451
|first_author = Nicole VILMER and Tomin JAMES
|publish_date = 29 May 2023
|description = Linking electron populations escaping from the Sun with those that RHESSI detects.
|image=Icon451.png}}

{{Nugget Badge
|title = Solar flare hard X-rays from the anchor points of an eruptive filament
|number = 450
|first_author = Muriel STIEFEL
|publish_date = 15 May 2023
|description = A rare "four-ribbon" flare has been detected in hard X-rays.
|image=Icon450.png}}

{{Nugget Badge
|title = Did a Solar Flare Accelerate all the Ambient Electrons in the Coronal Acceleration Region?...
|number = 449
|first_author = Gordon EMSLIE, Eduard KONTAR,
|second_author = Galina MOTORINA, and Brian DENNIS
|publish_date = 1 May 2023
|description = Considering SOL2017-09-10, probably not.
|image=Icon449.png}}

{{Nugget Badge
|title = Diagnostics of Spatially-Extended Turbulent Acceleration and Transport
|number = 448
|first_author = Morgan STORES
|publish_date = 24 April 2023
|description = Drilling down into the detailed structure of solar-flare energy release by including turbulence with particle acceleration.
|image=Icon448.png}}

{{Nugget Badge
|title = RHESSI's Re-entry
|number = 447
|first_author = Pascal SAINT-HILAIRE and
|second_author = Hugh HUDSON
|publish_date = 17 April 2023
|description = The final demise of RHESSI is this week
|image=Icon447.png}}

{{Nugget Badge
|title = A Glasgow geomagnetic observation of a solar flare
|number = 446
|first_author = Hugh HUDSON, John MALONE-LEIGH,
|second_author = Graham WOAN, and Chris OSBORNE
|publish_date = 13 March 2023
|description = Irish and Scottish geomagnetic observatories see a crochet much like that of the Carrington event
|image=Icon_446.png}}

{{{Nugget Badge
|title = Particle Acceleration in Two Coronal Jets
|number = 445
|first_author = Yixian ZHANG
|publish_date = 27 February 2023
|description = Coronal jets with hard X-ray sources at disjoint locations
|image=Icon445.png}}

{{Nugget Badge
|title = The Curious First Sunquake of Solar Cycle 25‎
|number = 444
|first_author = Alexander KOSOVICHEV
|publish_date = 13 February 2023
|description = A double whammy: two distinct sunquakes from SOL2022-05-10.
|image=Icon444.png}}

{{Nugget Badge
|title = Hard X-ray Pulsations via Gaussian Decomposition
|number = 443
|first_author = Hannah COLLIER and Laura HAYES
|publish_date = 30 January 2023
|description = Flare hard X-ray time variations decomposed objectively
|image=Icon443.png}}

{{Nugget Badge
|title = A possible coronal magnetic flare precursor
|number = 442
|first_author = Enrico LANDI
|publish_date = 16 January 2023
|description = Novel measurements of the coronal magnetic field may help with flare prediction
|image=Icon442.png}}

{{Nugget Badge
|title = A slow HOPE with microwave context
|number = 441
|first_author = Hugh HUDSON
|publish_date = 12 December 2022
|description = A new microwave facility at Chashan Observatory, and a prototypical HOPE
|image=Icon441.png}}

{{Nugget Badge
|title = Rapid variations of Si IV spectra in a flare observed by IRIS at a sub-second cadence
|number = 440
|first_author = Juraj LÖRINČÍK
|publish_date = 14 November 2022
|description = Transition-region lines in a flare have a Doppler component revealing quasi-periodic pulsations
|image=Icon440.png}}

{{Nugget Badge
|title = A Significant Sudden Ionospheric Disturbance Associated with a Massive Gamma-ray Burst
|number = 439
|first_author = Laura HAYES and Peter GALLAGHER
|publish_date = 31 October 2022
|description = A first SID observed in broad daylight, from a source far far away
|image=Icon439.png}}

{{Nugget Badge
|title = Effects of Coronal Structures on the Dynamics of the Global Coronal Wave of SOL2017-09-10‎
|number = 438
|first_author = Huidong HU, Ying D. LIU, and Bei ZHU
|publish_date = 17 October 2022
|description = The amazing global coronal wave of SOL2017-09-10 wrapped around the whole Sun, and displayed transmission and reflection at both polar coronal holes
|image=Icon438.png}}

{{Nugget Badge
|title = KW-Sun: The Konus-Wind Solar Flare Database in Hard X-Ray and Soft Gamma-Ray Ranges
|number = 437
|first_author = Alexandra LYSENKO
|publish_date = 26 September 2022
|description = An unrivaled hard X-ray and gamma-ray database is entering its third activity maximum
|image=Icon437.png}}

{{Nugget Badge
|title = First Detection of Kink Oscillations with Solar Orbiter
|number = 436
|first_author = Sihui ZHONG et al.
|publish_date = 19 September 2022
|description = SolO sees coronal oscillations as well as AIA can, and even better
|image=Icon436.png}}

{{Nugget Badge
|title = Energetic Neutral Hydrogen from Large Solar Flares
|number = 435
|first_author = Glenn MASON
|publish_date = 6 September 2022
|description = A rediscovered data treasury reveals the occurrence of many flare/CME events producing solar high-energy neutral atoms
|image=Icon435.png}}

{{Nugget Badge
|title = Fifty-year Anniversary of the First Detection of Gamma rays from a Solar Flare
|number = 434
|first_author = Jim Ryan,
|second_author = Brian Dennis, and Phil Dunphy
|publish_date = 8 August 2022
|description = The rich astrophysics of gamma-ray astronomy began with solar observations fifty years ago
|image=Icon434.png}}

{{Nugget Badge
|title = Fast Prograde Flows in Solar Active Regions
|number = 433
|first_author = Hugh HUDSON
|publish_date = 25 July 2022
|description = Unexpected, unpredicted, and not modeled yet - weird flows in hot active-region loops
|image=Icon433.png}}

{{Nugget Badge
|title = Undetected Minority-polarity Flux, Moss, and Coronal Heating
|number = 432
|first_author = Yi-Ming WANG
|publish_date = 11 July 2022
|description = There's plenty of room in "unipolar" active regions for both polarities, and there is good evidence for them
|image=Icon432.png}}

{{Nugget Badge
|title = Thermal/Nonthermal with MinXSS and RHESSI
|number = 431
|first_author = Shunsaku NAGASAWA
|publish_date = 13 June 2022
|description = Time-domain studies of improved X-ray spectra reveal a "super-hot' component
|image=Icon431.png}}

{{Nugget Badge
|title = Sun-as-a-star spectroscopic observations of the line-of-sight velocity of a solar eruption on October 28, 2021
|number = 430
|first_author = Yu XU
|second_author = and Hui TIAN
|publish_date = 30 May 2022
|description = The observation of the full 3d velocity of a CME, for an anniversary event
|image=Icon430.png}}

{{Nugget Badge
|title = Carl Størmer
|number = 429
|first_author = Hugh HUDSON
|second_author = and Lyndsay FLETCHER
|publish_date = 15 April 2022
|description = Størmer and the theory of trapping in loops
|image=Icon429.png}}

{{Nugget Badge
|title = Solar Hard X-rays with Insight
|number = 428
|first_author = Wei WANG
|second_author = and Ping ZHANG
|publish_date = 21 March 2022
|description = A spectacular limb flare introduces Insight/HXMT, a new observational resource
|image=Icon428.png}}

{{Nugget Badge
|title = Probing chromospheric current sheets using SST and ALMA co-observations
|number = 427
|first_author = João da SILVA SANTOS
|publish_date = 21 February 2022
|description = Emerging magnetic flux appears in ALMA images reflecting coronal current sheets
|image=Icon427.png}}

{{Nugget Badge
|title = A demonstration of STIX hard X-ray imaging spectroscopy capabilities for an X-class flare (SOL2021-10-28)
|number = 426
|first_author = Andrea BATTAGLIA, Hannah COLLIER,
|second_author = and Säm KRUCKER
|publish_date = 7 February 2022
|description = STIX imaging of an X-class flare marks its success
|image=Icon426.png}}

{{Nugget Badge
|title = A solar flare driven by thermal conduction observed in mid-infrared
|number = 425
|first_author = Guillermo GIMÉNEZ de CASTRO
|publish_date = 24 January 2022
|description = Strong 10-micron emission from a GOES C2 flare suggests conductive heating
|image=Icon425.png}}

{{Nugget Badge
|title = Disk Occultation of a Lopsided Sun‎
|number = 424
|first_author = Hugh HUDSON,
|second_author = Stephen WHITE and Säm KRUCKER
|publish_date = 10 January 2022
|description = Observing a spotless Sun can enable observations of the faint corona.
|image=Icon424.png}}

{{Nugget Badge
|title = Resolving two distinct thermal X-ray components in a compound solar flare
|number = 423
|first_author = Zhenjun ZHOU
|second_author = and Rui LIU
|publish_date = 28 December 2021
|description = Superhot coronal sources may be independent loop systems
|image=Icon423.png}}

{{Nugget Badge
|title = Bridging solar flares to coronal mass ejections
|number = 422
|first_author = Markus ASCHWANDEN
|publish_date = 14 December 2021
|description = The Neupert effect allows us to trace coronal mass ejections seamlessly
|image=Icon422.png}}

{{Nugget Badge
|title = The Jakimiec Diagnostic Diagram
|number = 421
|first_author = Hugh HUDSON
|publish_date = 29 November 2021
|description = The joint variation of GOES temperature and emission measure discloses new features via an old tool
|image=Icon421.png}}

{{Nugget Badge
|title = First look at ALMA/HInode/IRIS microflares
|number = 420
|first_author = Toshifumi SHIMIZU
|second_author = et al.
|publish_date = 8 November 2021
|description = High-resolution ALMA and multiwavelength observations of microflaring
|image=Icon420.png}}

{{Nugget Badge
|title = Thomson scattering near sunspots
|number = 419
|first_author = Pascal Saint-Hilaire
|second_author = et al.
|publish_date = 25 October 2021
|description = Completing the modeling of low-coronal Thomson polarimetry
|image=Icon419.png}}

{{Nugget Badge
|title = A Non-PFSS Global Coronal Model
|number = 418
|first_author = Oliver RICE
|second_author = and Anthony YEATES
|publish_date = 11 October 2021
|description = Modeling as convenient as PFSS but much more realistic
|image=Icon418.png}}

{{Nugget Badge
|title = Manifold Nonthermality
|number = 417
|first_author = Marina BATTAGLIA
|second_author = et al.
|publish_date = 27 September 2021
|description = Even weak flares involve multiple sites of non thermal activity
|image=Icon417.png}}

{{Nugget Badge
|title = X-Rays from a Type I Radio Burst
|number = 416
|first_author = R. RAMESH
|publish_date = 20 September 2021
|description = A first identification of type I radio emission with hot plasma
|image=Icon416.png}}

{{Nugget Badge
|title = Do Hot Onsets Predict Flare Magnitudes?
|number = 415
|first_author = Hugh HUDSON
|publish_date = 30 August 2021
|description = Maybe we can tell how big a flare is going to be from its initial development...
|image=Icon415.png}}

{{Nugget Badge
|title = Confined or Eruptive?
|number = 414
|first_author = Ting LI et al.
|publish_date = 16 August 2021
|description = Increased magnetic flux reduces CME eruptivity
|image=Icon414.png}}

{{Nugget Badge
|title = Impulsive and Gradual Eruptive Gamma Flares and Associated CMEs
|number = 413
|first_author = Alexey STRUMINSKY,
|second_author = Irina GRIGORIEVA and Andrei SADOVSKI
|publish_date = 19 July 2021
|description = Extreme behavior of flare/CME events explained by environment
|image=Icon373.png}}

{{Nugget Badge
|title = The Morphology of Flare Time Profiles
|number = 412
|first_author = Larisa KASHAPOVA
|second_author = et al.
|publish_date = 12 July 2021
|description = Systematic comparison of solar and stellar flaring time profiles
|image=Icon412.png}}

{{Nugget Badge
|title = Flare Pulsation and the Heliosphere
|number = 411
|first_author = Brendan CLARKE
|second_author = et al.
|publish_date = 5 July 2021
|description = Flare pulsations link closely to the distant heliosphere
|image=Icon411.png}}

{{Nugget Badge
|title = STIX, the Hard X-Ray Telescope on board Solar Orbiter
|number = 410
|first_author = Andrea Francesco BATTAGLIA
|second_author = and Säm KRUCKER
|publish_date = 28 June 2021
|description = STIX is operational and producing great data
|image=Icon410.png}}

{{Nugget Badge
|title = Nonequilibrium Ionization of Flare Plasma Observed by Hinode/EIS
|number = 409
|first_author = Shinsuke IMADA
|second_author =
|publish_date = 14 June 2021
|description = Evidence for non-equilibrium ionization in the current sheet of SOL2017-09-10
|image=Icon409.png}}

{{Nugget Badge
|title = Effects of Flares on Solar p-modes
|number = 408
|first_author = Maria-Cristina RABELLO SOARES
|second_author = and Frederic BAUDIN
|publish_date = 26 April 2021
|description = No detectable p-mode amplitude changes due to solar flares
|image=Icon408.png}}

{{Nugget Badge
|title = Subsecond Spikes in Solar Flare X-ray Flux as Seen by Fermi GBM
|number = 407
|first_author =Trevor KNUTH
|second_author = and Lindsay GLESENER
|publish_date = 19 April 2021
|description = A new analysis technique pushes hard X-ray time scales to 0.1 sec or faster
|image=Icon407.png}}

{{Nugget Badge
|title = Negative He 10830 Flare Ribbons and Non-thermal Electrons
|number = 406
|first_author = Graham KERR
|second_author =
|publish_date = 12 April 2021
|description = A 1D radiation hydrodynamics model can explain the dark leading edges of He I flare ribbons
|image=Icon406.png}}

{{Nugget Badge
|title = Tracing the sources of gradual solar energetic particle events
|number = 405
|first_author = David H. BROOKS
|second_author = and Stephanie L. YARDLEY
|publish_date = 29 March 2021
|description = Chemical abundances in SEPs suggest an origin in flare-related moss regions
|image=Icon405.png}}

{{Nugget Badge
|title = The Superflare SOL2017-09-06: from submm to mid-IR
|number = 404
|first_author = Guillermo (Guigue) GIMÉNEZ DE CASTRO
|second_author =
|publish_date = 15 March 2021
|description = Glimpsing the "missing decades" of the flare emission spectrum
|image=Icon404.png}}

{{Nugget Badge
|title = The Neupert Effect Revisited
|number = 403
|first_author = Jiong QIU
|second_author =
|publish_date = 8 March 2021
|description = Two time scales for heating individual flare strands
|image=Icon403.png}}

{{Nugget Badge
|title = FLUKA as a tool for interpreting flare gamma-rays
|number = 402
|first_author = Alec MACKINNON
|second_author =
|publish_date = 1 March 2021
|description = The nuclear physics of solar flares captured in a detailed model
|image=Icon402.png}}

{{Nugget Badge
|title = A Collective Study of 11 NuSTAR Microflares
|number = 401
|first_author = Jessie DUNCAN and
|second_author = Lindsay GLESENER
|publish_date = 22 February 2021
|description = Swarms of NuSTAR micro flares
|image=Icon401.png}}

{{{{Nugget Badge
|title = A Solar FRB
|number = 400
|first_author = Dale GARY and
|second_author = Hugh HUDSON
|publish_date = 15 February 2021
|description = A new frontier in the solar time domain
|image=Icon400.png}}

{{Nugget Badge
|title = Richard Schwartz
|number = 399
|first_author = Brian DENNIS and
|second_author = Hugh HUDSON
|publish_date = 25 January 2021
|description = Remembering a friend and colleague
|image=Icon399.jpg}}

{{Nugget Badge
|title = Observing Solar Flare X-ray Polarization with Prospective CubeSat Missions
|number = 398
|first_author = Natasha JEFFREY
|publish_date = 4 January 2021
|description = The polarization of the solar X-ray spectrum generally remains to be observed
|image=Icon398.png}}

{{Nugget Badge
|title = Solar effects in the local interstellar medium
|number = 397
|first_author = Don GURNETT and
|second_author = Hugh HUDSON
|publish_date = 14 December 2020
|description = Relativistic particle events observed _in situ_ in the interstellar medium
|image=Icon397.png}}

{{Nugget Badge
|title = Investigation of Small-Scale Energy Releases in Hard X-rays with FOXSI
|number = 396
|first_author = Subramania ATHIRAY and
|second_author = Juliana VIEVERING
|publish_date = 7 December 2020
|description = Hard X-rays and high temperatures from the feeblest microflares
|image=Icon396.png}}

{{Nugget Badge
|title = What drives impulsive coronal heating?
|number = 395
|first_author = Pradeep CHITTA
|second_author = et al.
|publish_date = 30 November 2020
|description = Impulsive footpoint emissions suggest magnetic reconnection in the chromosphere
|image=Icon395.png}}

{{Nugget Badge
|title = Probing the solar coronal heating function with slow magnetoacoustic waves
|number = 394
|first_author = Dmitrii KOLOTKOV
|second_author = et al.
|publish_date = 16 November 2020
|description = Coronal heating models meet damped slow magnetoacoustic waves
|image=Icon394.png}}

{{Nugget Badge
|title = Self-Consistent Flare Model
|number = 393
|first_author = Wenzhi RUAN
|second_author = and Rony KEPPENS
|publish_date = 2 November 2020
|description = Energy transport by fast particles made self-consistent with MHD flare modeling
|image=Icon393.png}}

{{Nugget Badge
|title = Hot Flare Onsets
|number = 392
|first_author = Hugh HUDSON
|second_author = et al.
|publish_date = 26 October 2020
|description = The initial soft X-ray temperatures of solar flares tend to be in the 10-15 MK range
|image=Icon392.png}}

{{Nugget Badge
|title = Electric Current Neutralization and Eruption
|number = 391
|first_author = Ellis AVALLONE
|second_author = and Xudong SUN
|publish_date = 19 October 2020
|description = Coronal currents without neutralizing return currents appear to
|image=Icon391.png}}

{{Nugget Badge
|title = Prediction of Solar Cycle 25
|number = 390
|first_author = Leif SVALGAARD
|second_author =
|publish_date = 5 October 2020
|description = Now we know how big the next solar maximum will be
|image=Icon390.png}}

{{Nugget Badge
|title = Flare/CME Cartoon Archive
|number = 389
|first_author = Hugh HUDSON
|second_author =
|publish_date = 27 September 2020
|description = A new edition of the Flare/CME archive, nearly a half kilotoon now
|image=Icon389.png}}

{{Nugget Badge
|title = Submerged Flare Acoustic Sources
|number = 388
|first_author = Juan Camilo BUITRAGO CASAS
|second_author = and Angel MARTÍNEZ
|publish_date = 13 September 2020
|description = Flare acoustic radiation emanates from a source _inside_ the Sun
|image=Icon388.png}}

{{Nugget Badge
|title = Circular Ribbon Flare at Microwaves
|number = 387
|first_author = Jeongwoo LEE
|second_author =
|publish_date = 31 August 2020
|description = Breakout reconnection reveals itself via microwave polarization measurements.
|image=Icon387.png}}

{{Nugget Badge
|title = Relation of Non-neutralized electric currents and the activity in active regions
|number = 386
|first_author = P. VEMAREDDY
|second_author =
|publish_date = 24 August 2020
|description = Non-neutralized coronal current systems contribute to CME eruptions
|image=Icon386.png}}

{{Nugget Badge
|title = White-light emission and photospheric magnetic field changes in flares
|number = 385
|first_author = J. Sebastián CASTELLANOS DURÁN
|second_author = and Lucia KLEINT
|publish_date = 17 August 2020
|description = There are strong correlations between white-light flare emissions and line-of-sight magnetic field changes
|image=Icon385.png}}

{{Nugget Badge
|title = Sunspot Differential Rotation in an X-class Flare
|number = 384
|first_author = Richard GRIMES,
|second_author = Balázs PINTÉR and Huw MORGAN
|publish_date = 10 August 2020
|description = Observations suggesting how the coronal tail can wag the photospheric dog
|image=Icon384.png}}

{{Nugget Badge
|title = Energy Partitioning in a Nonthermally Dominated Two-loop Solar Flare
|number = 383
|first_author = Galina MOTORINA
|second_author = et al.
|publish_date = 3 August 2020
|description = Modeling the propagation of energy via GX Simulator in an early-impulsive flare
|image=Icon383.png}}

{{Nugget Badge
|title = SOL2013-11-10 Eruptive Circular-ribbon Flare with Extended Remote Brightenings
|number = 382
|first_author = Chang LIU
|second_author = et al.
|publish_date = 31 July 2020
|description = A circular-ribbon event can launch an eruption by breaking through its separatrix dome
|image=Icon382.png}}

{{Nugget Badge
|title = Extreme-Ultraviolet Late Phase of Solar Flares
|number = 381
|first_author = Rui LIU
|second_author =
|publish_date = 22 June 2020
|description = Both arcade and circular-ribbon flares may sometimes spawn EUV late phase emission
|image=Icon381.png}}

{{Nugget Badge
|title = Energy transport by accelerated particles in the quiet solar atmosphere
|number = 380
|first_author = Lars FROGNER,
|second_author = Boris GUDIKSEN and Helle BAKKE
|publish_date = 15 June 2020
|description = A first study of non-thermal particles integrated into an MHD simulation of the solar atmosphere
|image=Icon380.png}}

{{Nugget Badge
|title = Quasi-periodic pulsations as indicators of oscillatory processes in solar flares
|number = 379
|first_author = Elena KUPRIYANOVA
|second_author = et al.
|publish_date = 11 May 2020
|description = Many, many QPPs
|image=Icon379.png}}

{{Nugget Badge
|title = Rejuvenating Solar Flare Termination Shocks as Particle Accelerators
|number = 378
|first_author = Bin CHEN
|second_author =
|publish_date = 4 May 2020
|description = At last, clear evidence for a long-predicted phenomenon
|image=Icon378.png}}

{{Nugget Badge
|title = Broad symmetrical Doppler-shifted Fe XXI line profiles
|number = 377
|first_author = Vanessa POLITO
|second_author =
|publish_date = 20 April 2020
|description = It is difficult to explain "evaporation" line profiles by superposition of unresolved flows
|image=Icon377.png}}

{{Nugget Badge
|title = Phenomena in the unusually long pre-impulsive phase of SOL2011-06-07
|number = 376
|first_author = Marian KARLICKÝ,
|second_author = Jana KA&Scaron;PAROVÁ, and Robert SYCH
|publish_date = 13 April 2020
|description = A massive and slowly-rising filament eruption reveals important new signatures of the physics
|image=Icon376.png}}

{{Nugget Badge
|title = Evidence for a Coronal Shock Wave Origin for Relativistic Protons Producing Solar Gamma-Rays and Observed by Neutron Monitors at Earth‎
|number = 375
|first_author = Athanasios KOULOUMVAKOS
|second_author = and Gerry SHARE
|publish_date = 6 April 2020
|description = Successful modeling of prolonged solar gamma-ray emissions and terrestrial ground-level cosmic-ray events
|image=Icon375.png}}

{{Nugget Badge
|title = Using overlappogram data to find hot flare plasma
|number = 374
|first_author = Louise HARRA
|
|publish_date = 23 March 2020
|description = Imaging Fe XXIV at high resolution with the EIS slot data
|image=Icon374.png}}

{{Nugget Badge
|title = SOL2017-09-04 (M5.5) 2017 as a Source of Relativistic Electrons and Protons
|number = 373
|first_author = Alexei STRUMINSKII
| (see text)
|publish_date = 16 March 2020
|description = Flare-accelerated particles, rather than SEPs, energize sustained gamma-ray emission
|image=Icon373.png}}

{{Nugget Badge
|title = Heating of the solar photosphere during a white-light flare‎
|number = 372
|first_author = Jan JURČÁK
| (see text)
|publish_date = 2 March 2020
|description = The best-ever spectrum of the flare photosphere
|image=Icon372.png}}

{{Nugget Badge
|title = A Hot Cusp-Shaped Confined Solar Flare
|number = 371
|first_author = Aaron HERNANDEZ-PEREZ
|publish_date = 24 February 2020
|description = A flare may have a prominent hot cusp with the help of any eruption
|image=Icon371.png}}

{{Nugget Badge
|title = The Temporal and Spatial Extension of Gamma-ray Emission from the Sun
|number = 370
|first_author = Nat GOPALSWAMY
|publish_date = 17 February 2020
|description = Sustained solar γ-rays and solar cosmic rays
|image=Icon370.ng.png}}

{{Nugget Badge
|title = A PSP Perihelion
|number = 369
|first_author = Jessie DUNCAN
|second_author = and Hugh Hudson
|publish_date = 20 January 2020
|description = The Parker Solar Probe enters its fourth perihelion already. Now
|image=Icon369.png}}

{{Nugget Badge
|title = Remembering John Brown
|number = 368
|first_author = Alec MacKINNON
|second_author =
|publish_date = 13 January 2020
|description = John passed away unexpectedly on 16 November 2019
|image=Icon368.png}}

{{Nugget Badge
|title = A Global Survey of EUV Coronal Power Spectra
|number = 367
|first_author = Karl Battams
|second_author =
|publish_date = 30 December 2019
|description = Time-series parameter maps of imaged power spectra from an AIA pipeline
|image=Icon367.png}}

{{Nugget Badge
|title = Cosmic Rays over the Rainbow Bridge
|number = 366
|first_author = Hugh Hudson
|second_author = Alec MacKinnon
|publish_date = 16 December 2019
|description = Cosmic rays approach the Sun
|image=Icon366.png}}

{{Nugget Badge
|title = Spectropolarimetric Insight into Plasma-Sheet Dynamics of a Solar Flare
|number = 365
|first_author = Ryan French
|second_author =
|publish_date = 9 December 2019
|description = CoMP polarization patterns in SOL2017-09-10 are amazing
|image=Icon365.png}}

{{Nugget Badge
|title = Lorentz Force Evolution Reveals the Energy Build-up Processes during Recurrent Eruptive Solar Flares‎
|number = 364
|first_author = Ranadeep Sarkar,
|second_author = Nandita Srivastava and Astrid Veronig
|publish_date = 18 November 2019
|description = The net Lorentz force clearly exhibits a build-up and release pattern
|image=Icon364.png}}

{{Nugget Badge
|title = Flare waiting times depend on their magnitudes
|number = 363
|first_author = Hugh Hudson
|second_author =
|publish_date = 11 November 2019
|description = Surprising new evidence for the flare build-up and release process
|image=Icon363.png}}

{{Nugget Badge
|title = Can magnetic reconnection cause solar rainstorms?‎
|number = 362
|first_author = Petra Kohutova
|second_author =
|publish_date = 4 November 2019
|description = Impulsive coronal heating resulting from reconnection can trigger coronal rain
|image=Icon362.png}}

{{Nugget Badge
|title = Non-radial jets on the edges of active regions
|number = 361
|first_author = Peter Wyper
|second_author =
|publish_date = 14 October 2019
|description = The very common jet structures we see can naturally combine twist and breakout
|image=Icon361.png}}

{{Nugget Badge
|title = Searching SOLfully within the Nuggets
|number = 360
|first_author = Hugh Hudson
|second_author =
|publish_date = 7 October 2019
|description = The IAU target identifier works well for finding items about a particular event
|image=Icon360.png}}

{{Nugget Badge
|title = Submillimeter Radiation as the Thermal Component of the Neupert Effect
|number = 359
|first_author = Guillermo Giménez de Castro
|second_author =
|publish_date = 31 September 2019
|description = Flare radiation at the highest frequencies can be bremsstrahlung
|image=Icon359.png}}

{{Nugget Badge
|title = The "Last Best" Flares
|number = 358
|first_author = Hugh Hudson,
|second_author = Ed Cliver, and Brian Dennis
|publish_date = 24 September 2019
|description = Major flares tend to happen at the very ends of sunspot cycles
|image=Icon358.png}}

{{Nugget Badge
|title = Dynamic Processes of the Moreton Wave on 2014 March 29‎
|number = 357
|first_author = Denis Cabezas
|second_author = and the FMT team
|publish_date = 16 September 2019
|description = A beautiful Moreton wave excited by the best-observed flare ever
|image=Icon357.png}}

{{Nugget Badge
|title = EVE-RHESSI DEM Models and the Low-energy Cutoff for Nonthermal Electrons
|number = 356
|first_author = Jim McTiernan
|second_author =
|publish_date = 9 September 2019
|description = Characterizing flare temperature distributions helps to define the non-thermal energy release
|image=Icon356.png}}

{{Nugget Badge
|title = Stealth Coronal Mass Ejections from Active Regions
|number = 355
|first_author = Jennifer O'Kane
|second_author =
|publish_date = 26 August 2019
|description = Perhaps just feeble versions of the same magnetic disease...
|image=Icon355.png}}

{{Nugget Badge
|title = Do Kepler Superflare Stars Really Include Slowly Rotating Sun-like Stars?‎
|number = 354
|first_author = Yuta NOTSU
|second_author =
|publish_date = 15 July 2019
|description = Kepler superflares hint at solar superflares
|image=Icon354.png}}

{{Nugget Badge
|title = Localized Microwave and EUV Bright Structures in an Eruptive Prominence
|number = 353
|first_author = Jing HUANG
|second_author =
|publish_date = 22 June 2019
|description = Detailed correlations between EUV and microwaves in prominence fine structures
|image=Icon353.png}}

{{Nugget Badge
|title = Broken-up hard X-ray spectra found for a loop-top source during a solar limb flare
|number = 352
|first_author = Hao NING,
|second_author = Yao CHEN and Jeongwoo LEE
|publish_date = 16 June 2019
|description = SOL2017-09-10 coronal hard X-ray sources
|image=Icon352.png}}

{{Nugget Badge
|title = The Cosmic-Ray Shadow and Coronal Magnetism
|number = 351
|first_author = Frederik Tenholt
|second_author =
|publish_date = 27 May 2019
|description = The coronal magnetic field measured in Antarctica
|image=Icon351.png}}

{{Nugget Badge
|title = Kristian Birkeland
|number = 350
|first_author = Hugh HUDSON
|second_author = and Lyndsay FLETCHER
|publish_date = 6 May 2019
|description = Space weather a century ago: Kristian Birkeland
|image=Icon350.png}}

{{Nugget Badge
|title = Warm UV loops heated by small-scale cancellation events
|number = 349
|first_author = Seray ŞAHIN
|second_author = and Vasyl YURCHYSHYN
|publish_date = 22 April 2019
|description = Precisely locating the footpoints of warm coronal loops helps identify their source(s) of excitation
|image=Icon349.png}}

{{Nugget Badge
|title = Multiple Regions of Shock-accelerated Particles during a Solar Coronal Mass Ejection
|number = 348
|first_author = Diana MOROSAN
|second_author =
|publish_date = 1 April 2019
|description = LOFAR identifies herringbone sources within the flank of the SOL2017-09-10 shock - no joke
|image=Icon348.png}}

{{Nugget Badge
|title = Persistent Quasi-Periodic Pulsations Detected During the Large X8.2 Solar Flare
|number = 347
|first_author = Laura HAYES
|second_author = and Peter GALLAGHER
|publish_date = 25 March 2019
|description = The most beautiful flare has the most beautiful pulsations
|image=Icon347.png}}

{{Nugget Badge
|title = Is the coronal magnetic field braiding?
|number = 346
|first_author = Markus ASCHWANDEN
|second_author =
|publish_date = 11 March 2019
|description = This iconic cartoon does not relate well to the observations
|image=Icon346.png}}

{{Nugget Badge
|title = An energetic pre-flare: electron distributions in magnetic reconnection outflows
|number = 345
|first_author = Marina BATTAGLIA,
|second_author = Eduard KONTAR and Galina MOTORINA
|publish_date = 18 February 2019
|description = Assessing energy partition in a pre-impulsive flare development
|image=Icon345.png}}

{{Nugget Badge
|title = Linear Polarization in H-alpha Flares
|number = 344
|first_author = Tomoko KAWATE
|second_author = and Yoichiro HANAOKA
|publish_date = 4 February 2019
|description = H-alpha polarization is rarely observable but, in once case, very suggestive
|image=Icon344.png}}

{{Nugget Badge
|title = Short-Period Waves
|number = 343
|first_author = Sijie YU
|second_author = and Bin CHEN
|publish_date = 21 January 2019
|description = New decimetric imaging spectroscopy suggests Alfvénic energy transport in flares
|image=Icon343.png}}

{{Nugget Badge
|title = The Interesting RHESSI/SAS Archive
|number = 342
|first_author = Hugh HUDSON
|second_author = and Martin FIVIAN
|publish_date = 8 January 2019
|description = The full mission database shows RHESSI to have been very stable geometrically
|image=Icon342.png}}

{{Nugget Badge
|title = Homologous White Light Solar Flares‎
|number = 341
|first_author = Paolo ROMANO
|second_author = and Abouazza ELMHAMDI
|publish_date = 31 December 2018
|description = Homologous white-light flares, in rapid succession, and coronal null points
|image=Icon341.png}}

{{Nugget Badge
|title = The flight of FOXSI-3
|number = 340
|first_author = Lindsay GLESENER
|second_author = and Noriyuki NARUKAGE
|publish_date = 10 December 2018
|description = Single-photon counting and direct focusing across hard and soft energies
|image=Icon340.png}}

{{Nugget Badge
|title = Stellar Flares and Starspots
|number = 339
|first_author = Lauren DOYLE
|second_author =
|publish_date = 3 December 2018
|description = Stellar flares don't spatially match their starspots
|image=Icon339.png}}

{{Nugget Badge
|title = Neutron Production in Solar Flares
|number = 338
|first_author = Ron MURPHY
|second_author = and Gerry SHARE
|publish_date = 26 November 2018
|description = Neutron astronomy helps us understand solar flares
|image=Icon338.png}}

{{Nugget Badge
|title = Cycle 25 Strikes Again
|number = 337
|first_author = Kamil BICZ
|second_author =
|publish_date = 20 November 2018
|description = A second, larger Cycle 25 sunspot
|image=Icon337.png}}

{{Nugget Badge
|title = Remembering Marcos Machado via his research
|number = 336
|first_author = Hugh HUDSON
|second_author =
|publish_date = 13 November 2018
|description = Recalling a friend and colleague, and admiring his final paper
|image=Icon336.png}}

{{Nugget Badge
|title = CORONAS/SPIRIT Mg XII and Nanoflares‎
|number = 335
|first_author = Anton REVA
|second_author =
|publish_date = 22 October 2018
|description = Monochromatic Mg XII spectroheliography sets severe limits on nanoflare heating models
|image=Icon335.png}}

{{Nugget Badge
|title = White-light Emission and Non-thermal Electrons‎
|number = 334
|first_author = Kyoung-Sun LEE
|second_author =
|publish_date = 8 October 2018
|description = An intimate relationship between accelerated electrons and visible flare continuum
|image=Icon334.png}}

{{Nugget Badge
|title = Coronal Hard X-ray Sources Revisited
|number = 333
|first_author = Brian DENNIS
|second_author =
|publish_date = 24 September 2018
|description = Reporting some over-interpretation of the evidence for "coronal thick targets"
|image=Icon333.png}}

{{Nugget Badge
|title = Photospheric response to a flare
|number = 332
|first_author = Mike WHEATLAND
|second_author =
|publish_date = 17 September 2018
|description = Sudden changes in the magnetic field in the low atmosphere associated with particle acceleration
|image=Icon332.png}}

{{Nugget Badge
|title = New Views of Global Solar Magnetic Field Evolution Over Four Solar Cycles
|number = 331
|first_author = David WEBB
|second_author =
|publish_date = 27 August 2018
|description = A digital archive of Pat McIntosh's 44 years of solar synoptic observations
|image=Icon331.png}}

{{Nugget Badge
|title = Understanding the co-spatial return current in solar flares
|number = 330
|first_author = Meriem ALAOUI
|second_author = and Gordon HOLMAN
|publish_date = 6 August 2018
|description = Completing the circuit in a thick-target model
|image=Icon330.png}}

{{Nugget Badge
|title = 3D Magnetic Reconnection at a Coronal Null Point
|number = 329
|first_author = Shane MALONEY,
|second_author = Aidan O'Flannagain and Peter Gallagher
|publish_date = 30 July 2018
|description = Large-scale reconnection involved in Type I radio noise storm
|image=Icon329.png}}

{{Nugget Badge
|title = The true dawn of multimessenger astronomy
|number = 328
|first_author = Hugh Hudson
|second_author =
|publish_date = 23 July 2018
|description = Ever since the Carrington flare
|image=Icon328.png}}

{{Nugget Badge
|title = Microwave Imaging Spectroscopy of Flares is Here‎
|number = 327
|first_author = Dale E. Gary,
|second_author = EOVSA and RHESSI Teams
|publish_date = 16 July 2018
|description = Microwave imaging spectroscopy takes a giant leap forward with SOL2017-09-10
|image=Icon327.png}}

{{Nugget Badge
|title = Coronal nanoflares powered by footpoint reconnection
|number = 326
|first_author = Pradeep Chitta,
|second_author = Hardi Peter, and Sami Solanki
|publish_date = 9 July 2018
|description = Coronal nanoflares in active region cores can be powered by the magnetic reconnection in the lower solar atmosphere
|image=Icon326.png}}

{{Nugget Badge
|title = A remarkable, but confused, coronal hard X-ray source
|number = 325
|first_author = Alexandra Lysenko,
|second_author = Larisa Kashapova and Hugh Hudson
|publish_date = 25 June 2018
|description = A remarkable flare in 1999 adds to our short list of extended coronal hard X-ray/microwave sources
|image=Icon325.png}}

{{Nugget Badge
|title = Understanding HMI pseudocontinuum in white-light flares‎
|number = 324
|first_author = Michal &Scaron;vanda
|second_author = et al.
|publish_date = 28 May 2018
|description = The HMI pseudocontinuum (Ic) is ill-calibrated in regions with strong fields, i.e. for white-light flares
|image=Icon324.png}}

{{Nugget Badge
|title = To beam or not to beam - that is (still) the question
|number = 323
|first_author = Paulo Simões
|second_author = and Hugh Hudson
|publish_date = 14 May 2018
|description = Descriptions of the lower solar atmosphere of flares ca. Cycle 21 sound surprisingly current
|image=Icon323.png}}

{{Nugget Badge
|title = Observation of Cosmic Ray Spallation Events from SoHO‎
|number = 322
|first_author = Serge Koutchmy
|second_author = and Ehsan Tavabi
|publish_date = 7 May 2018
|description = LASCO's images capture high-energy nuclear interactions from cosmic-ray hits
|image=Icon322.png}}

{{Nugget Badge
|title = A Sunspot from Cycle 25 for sure
|number = 321
|first_author = Tomek Mrozek
|second_author = and Hugh Hudson
|publish_date = 10 April 2018
|description = YES! Cycle 25 is here!
|image=Icon321.png}}

{{Nugget Badge
|title = Blue-wing enhancement of the Mg II h and k lines in a flare
|number = 320
|first_author = Akiko TEI
|second_author =
|publish_date = 9 April 2018
|description = Flare loops involve a cool upflow preceding the hot evaporation flow
|image=Icon320.png}}

{{Nugget Badge
|title = NuSTAR detects X-ray flares in the quiet Sun
|number = 319
|first_author = Matej Kuhar
|second_author = and Säm Krucker
|publish_date = 26 March 2018
|description = Quiet-Sun flares may not be powerful, but they look a lot like ordinary flares
|image=Icon319.png}}

{{Nugget Badge
|title = Homologous CME/flares from AR 12371
|number = 318
|first_author = Panditi Vemareddy
|second_author = and Pascal Demoulín
|publish_date = 19 March 2018
|description = An excellent set of homologous flare/CMEs analyzed and explained
|image=Icon318.png}}

{{Nugget Badge
|title = Non-Maxwellian Diagnostics from SDO/EVE Spectra of an X-class Flare
|number = 317
|first_author = Elena Dzifčáková
|second_author = and Jaroslav Dudík
|publish_date = 16 February 2018
|description = Ratios of high-excitation ions can readily detect κ-distributions in flare plasmas
|image=Icon317.png}}

{{Nugget Badge
|title = Joint MinXSS and RHESSI Flare X-ray Spectra between 1 and 15 keV
|number = 316
|first_author = Chris Moore, Brian Dennis and the MinXSS Science Team
|publish_date = 5 February 2018
|description = MinXSS adds systematic views of flare soft X-ray spectra to RHESSI imagery
|image=Icon316.png}}

{{Nugget Badge
|title = Parameterized Flare Models with Chromospheric Compressions
|number = 315
|first_author = Adam Kowalski & Joel Allred
|publish_date = 17 January 2018
|description = A new approach to modeling the lower flare atmosphere
|image=FlareModelsKowalskiAllred.png}}

{{Nugget Badge
|title = A Curious Sunspot Group in 2018
|number = 314
|first_author = Hugh Hudson
|publish_date = 14 January 2018
|description = The first new sunspot group of 2018 emerged at the wrong latitude
|image = Icon314.png}}

{{Nugget Badge
|title = Tecumseh's Eclipse and Astrophysics
|number = 313
|first_author = Hugh Hudson
|publish_date = 25 December 2017
|description = The solar corona was first recognized as such, and named, in an eclipse of 1806
|image = Icon313.png}}

{{Nugget Badge
|title = Hunting for Hidden Tiny Flares
|number = 312
|first_author = Shin-nosuke ISHIKAWA
|publish_date = 27 November 2017
|description = FOXSI-2 says that episodic energy releases are still viable as a part of the coronal heating problem.
|image = Icon312.png}}

{{Nugget Badge
|title = Unusual Type III Burst Dynamics Produced by Diverging Magnetic Fields
|number = 311
|first_author = Patrick McCauley
|publish_date = 20 November 2017
|description = Unusual type III bursts follow coronal separatrix structures.
|image = Icon311.png}}

{{Nugget Badge
|title = Valderrama in the 21st Century
|number = 310
|first_author = Hugh Hudson
|publish_date = 31 October 2017
|description = A newly-described white-light flare from the 19th century!..
|image = Icon310.png}}

{{Nugget Badge
|title = Electron Scattering in the Flaring Corona
|number = 309
|first_author = Sophie Musset
|publish_date = 24 October 2017
|description = Diffusive transport may contribute to the trapping of electrons in coronal X-ray sources
|image = Icon309.png}}

{{Nugget Badge
|title = The Power of Turbulence
|number = 308
|first_author = Nic Bian
|publish_date = 25 September 2017
|description = Turbulent energy content may underlie flare energy transfer, magnetic reconnection, and particle acceleration
|image = Icon308.png}}

{{Nugget Badge
|title = The Kelvin Force and Loop-Top Concentration
|number = 307
|first_author = Kiyoto SHIBASAKI
|publish_date = 18 September 2017
|description = New physics can explain the perplexing overpressure at the flare looptop regions
|image = Icon307.png}}

{{Nugget Badge
|title = The Last Best Flare of Cycle 24?
|number = 306
|first_author = Säm Krucker
|second_author = and Hugh Hudson
|publish_date = 11 September 2017
|description = Right on schedule, Cycle 24 has produced a great flare (with a GLE)
|image = Icon306.png}}

{{Nugget Badge
|title = Electric Current Neutralization and Solar Eruption in Active Regions
|number = 305
|first_author = Yang LIU
|second_author =
|publish_date = 28 August 2017
|description = Active current systems in the solar corona don't have return currents
|image = Icon305.png}}

{{Nugget Badge
|title = RHESSI and the Megamovie
|number = 304
|first_author = Hugh Hudson, Laura Peticolas,
|second_author = and Juan Carlos Martínez Oliveros
|publish_date = 31 July 2017
|description = A wholly new way to view a solar eclipse, and to do solar astrometry
|image = Icon304.png}}

{{Nugget Badge
|title = Bastille Day 2017
|number = 303
|first_author = Hugh Hudson
|second_author = and Säm Krucker
|publish_date = 24 July 2017
|description = Interesting flares really do happen on Bastille Day...
|image = Icon303.png}}

{{Nugget Badge
|title = The Solar X-ray Limb III
|number = 302
|first_author = Marina Battaglia
|second_author = and Gordon Hurford
|publish_date = 12 June 2017
|description = RHESSI succeeds with a wholly new way to measure the solar diameter
|image = Icon302.png}}

{{Nugget Badge
|title = Double Coronal X-ray and Microwave Sources Associated With A Magnetic Breakout Solar Eruption
|number = 301
|first_author = Yao CHEN
|second_author =
|publish_date = 29 May 2017
|description = A different explanation of the double coronal hard X-ray sources
|image = Icon301.png}}

{{Nugget Badge
|title = A Lasso Model for Solar Gamma-ray Events
|number = 300
|first_author = Hugh Hudson
|second_author =
|publish_date = 15 May 2017
|description = A toy model hoping to explain the SEP/LAT relationship
|image = Icon300.png}}

[[RHESSI Science Nuggets 200 to 299|Next Nuggets]]

SolarNuggets

2026-05-14T10:49:46Z

Hhudson: No. 526

Welcome to the [[SolarNuggets]] collection, which extends the series of [[RHESSI]] Nuggets. The following is a time-ordered list of the latest Nuggets added to the HelioWiki. An [[:Category:Nugget|alphabetical list of the SolarNuggets]] is also available as well as [[:Category:RHESSI Nugget List|yearly lists]]. One can search on author, topic, IAU flare identifier, etc.). We welcome volunteer authors - please see our page of [[Help:For_Authors| help for authors]] or just send an email to the Curator at (hugh.hudson@glasgow.ac.uk).

{{Nugget Badge
|title = {{Nugget Badge
|title = X-ray Log Letters‎‎
|number = 526
|first_author = Hugh HUDSON
|second_author = and Ed CLIVER
||publish_date = 18 May 2026
|description = Replacing ABCMX with a new comprehensive and quantitative QSabcmxyz catalog
|image=Icon526.png}}

{{Nugget Badge
|title = How Extreme Can Solar Flares Get? A Statistical View‎‎
|number = 525
|first_author = Lapo Ceccarelli
|second_author = and Daniela CASTRO-CAMILO
||publish_date = 4 May 2026
|description = A proper statistical treatment of the prospects for an extreme solar flare event
|image=Icon525.png}}

{{Nugget Badge
|title = Observations of Slow Elemental Abundance Decay in Association to CME
|number = 524
|first_author = Saara TAKALA
||publish_date = 27 April 2026
|description = Soft X-ray spectroscopy tracks coronal abundance variations associated with a CME
|image=Icon524.png}}

{{Nugget Badge
|title = An Unusual Long-Lived Radio Burst Oscillating in Frequency
|number = 523
|first_author = Marian KARLICKÝ,
|second_author = Robert SYCH and Alena ZEMANOVÁ
||publish_date = 20 April 2026
|description = Remarkable decimetric signatures of structured outflows from a flaring active region
|image=Icon523.png}}

{{Nugget Badge
|title = Lateral Deformation of Large-scale Coronal Mass Ejections during the Transition from Nonradial to Radial Propagation
|number = 522
|first_author = Huidong HU
||publish_date = 13 April 2026
|description = Coronal mass ejections can begin their trajectory highly tilted to the vertical, but then straighten out
|image=Icon522.png}}

{{Nugget Badge
|title = Can EUV Power-Spectral Indices Reveal Imminent Solar Flares?
|number = 521
|first_author = Sihui ZHONG,
|second_author = Dmitrii KOLOTKOV and Valery M. NAKARIAKOV
||publish_date = 6 April 2026
|description = A new flare-precursor observable - power spectra
|image=Icon521.png}}

{{Nugget Badge
|title = How energetic can solar flares become?
|number = 520
|first_author = Natalie KRIVOVA
||publish_date = 31 March 2026
|description = The history of active-region areas suggests the possibility of solar superflares
|image=Icon520.png}}

{{Nugget Badge
|title = Hinode EIS Observations of Plasma Composition Evolution and Radiative Cooling of Flare Loops
|number = 519
|first_author = Teodora MIHĂILESCU,
|second_author = Peter YOUNG et AL.
||publish_date = 16 March 2026
|description = Higher FIP bias than expected in some flare loops, a diagnostically interesting result
|image=Icon519.png}}

{{Nugget Badge
|title = When Magnetic Field Lines Stretch, Snap, and Expand: A New Look at Solar Flares with L-maps
|number = 518
|first_author = Maria KAZACHENKO,
|second_author = Yuhong FAN and Andrey AFANASYEV
||publish_date = 9 March 2026
|description = A clever new tool tracks magnetic connectivity (and energy) during flare/CME occurrence
|image=Icon518.png}}

{{Nugget Badge
|title = Observational Evidence Linking Loop Length and Thermal/Nonthermal Peak Timing in Solar Flares
|number = 517
|first_author = Solomon PERRIYIL
||publish_date = 23 February 2026
|description = Clear evidence for the universality of the physics behind the Neupert Effect
|image=Icon517.png}}

{{Nugget Badge
|title = A fine-scale bright kernel captured by Hi-C 3 in the post-maximum phase of an M-class solar flare
|number = 516
|first_author = Sanjiv TIWARI
||publish_date = 9 February 2026
|description = The Hi-C rocket catches an extremely compact brightening in late-phase flare ribbon development
|image=Icon516.png}}

{{Nugget Badge
|title = On the Relationship Between Nanoflare Energy and Delay in the Closed Solar Corona
|number = 515
|first_author = Shanwlee SOW MONDAL et al.
||publish_date = 19 January 2026
|description = Nanoflaring implies energy storage and sudden release, suggesting correlation between event energy and its timing
|image=Icon515.png}}

{{Nugget Badge
|title = Fine structures in solar flare ribbons
|number = 514
|first_author = Jonas THOEN FABER
||publish_date = 12 January 2026
|description = Elongated "riblets" commonly rise out of flare ribbons, and have characteristic Doppler shifts
|image=Icon514.png}}

{{Nugget Badge
|title = The M- and X-class White-light Flares in Super Active Region NOAA 13664/13697
|number = 513
|first_author = Zhichen JING
|second_author = and Ying LI
|publish_date = 5 January 2026
|description = "Super" active regions have relatively more frequent X-class flares, which correlate well with visible continuum (white-light flare) emission
|image=Icon513.png}}

{{Nugget Badge
|title = Iron Fluorescence in X-class Solar Flares
|number = 512
|first_author = Abhilash SARWADE
|publish_date = 8 December 2025
|description = A new spectroscopic capability for Iron K-alpha fluorescence
|image=Icon512.png}}

{{Nugget Badge
|title = Sun-as-a-star Analysis of a Solar Eruption Source Region Using H-alpha Spectroscopic Observations from CHASE
|number = 510
|first_author = Xiaofeng LIU
|second_author = and Yijun HOU
|publish_date = 24 November 2025
|description = Sun-as-a-star observations help to translate solar/stellar processes
|image=Icon5010.png}}

{{Nugget Badge
|title = On the Origin of Solar Long-Duration Gamma-Ray Flares‎‎‎‎
|number = 509
|first_author = Alessandro BRUNO
|publish_date = 3 November 2025
|description = Do we really need a CME to produce a long-duration solar gamma-ray event?
|image=Icon509.png}}

{{Nugget Badge
|title = FAI and GOES eclipses‎‎
|number = 508
|first_author = Hugh HUDSON
|publish_date = 20 October 2025
|description = Flare anticipation via FAI may have problems during GOES eclipses, which are really interesting in their own right
|image=Icon508.png}}

{{Nugget Badge
|title = The EUV Late Phase‎
|number = 507
|first_author = Sascha ORNIG
|publish_date = 13 October 2025
|description = Basic comparative statistics of the ELP, a distinct flare phenomenon
|image=Icon507.png}}

{{Nugget Badge
|title = Time evolution of flare-accelerated electrons using the warm-target model‎
|number = 506
|first_author = Debesh BHATTACHARJEE
|publish_date = 6 October 2025
|description = Considering a "warm" thick target allows flare-accelerated electrons to be treated self-consistently
|image=Icon506.png}}

{{Nugget Badge
|title = SOLSTICE observes flare Doppler shifts in Si III
|number = 505
|first_author = Luke MAJURY
|publish_date = 30 September 2025
|description = A rarely used database suggests prograde-flow Doppler shifts in flaring plasmas
|image=Icon505.png}}

{{Nugget Badge
|title = Flare Phases and the Earth's Ionospheric Response
|number = 504
|first_author = Susanna BEKKER
|publish_date = 16 September 2025
|description = A flare's "EUV late phase" is surprisingly geoeffective
|image=Icon504.png}}

{{Nugget Badge
|title = Neupertianity
|number = 503
|first_author = Hugh HUDSON
|publish_date = 25 August 2025
|description = It's hard to avoid the Neupert Effect
|image=Icon503.png}}

{{Nugget Badge
|title = Synchrotron Radiation and the Foundations for a Cosmic Bridge
|number = 502
|first_author = Immanuel JEBARAJ
|publish_date = 11 August 2025
|description = Gyrosynchrotron radiation in shocks: a cosmic connection
|image=Icon502.png}}

{{Nugget Badge
|title = The Aulanier Effect: drifting footpoints of CME flux ropes
|number = 501
|first_author = Jaroslav DUDÍK,
|second_author = Juraj LÖRINČÍK and Brigitte SCHMIEDER
|publish_date = 21 July 2025
|description = The breakthrough to 3D flare physics: the Aulanier Effect
|image=Icon501.png}}

{{Nugget Badge
|title = Five Hundred Nuggets
|number = 500
|first_author = Hugh HUDSON
|publish_date = 14 July 2025
|description = A milestone
|image=Icon169.png}}

{{Nugget Badge
|title = Quasiperiodic Pulsations in the Balmer Continuum in an X-class Solar White-light Flare
|number = 499
|first_author = De-Chao SONG et al.
|publish_date = 30 June 2025
|description = QPP in the Balmer continuum: the powerful heartbeat of a flare
|image=Icon499.png}}

{{Nugget Badge
|title = High-Resolution Observations of a C3 class White-Light Flare
|number = 498
|first_author = Zhe XU and
|second_author = Xiaoli YAN
|publish_date = 16 June 2025
|description = A compact white-light flare with vortical motions (and hard X-rays)
|image=Icon498.png}}

{{Nugget Badge
|title = The Sun's open-closed flux boundary and the origin of the slow solar wind
|number = 497
|first_author = Chloe WILKINS and
|second_author = David PONTIN
|publish_date = 26 May 2025
|description = Identifying the solar sources of slow solar wind
|image=Icon497.png}}

{{Nugget Badge
|title = Delay of Near-Relativistic Electrons
|number = 496
|first_author = Grant MITCHELL
|publish_date = 19 May 2025
|description = Parker Solar Probe solves an old mystery about type III bursts
|image=Icon496.png}}

{{Nugget Badge
|title = A Multi-Site Telescope for Multi-Height for Synoptic Observations
|number = 495
|first_author = Fallon KONOW
|publish_date = 11 May 2025
|description = A new synoptic network for observations at multiple wavelengths
|image=Icon495.png}}

{{Nugget Badge
|title = On turbulent magnetic reconnection: fast and slow mean steady-states
|number = 494
|first_author = Sage STANISH
|second_author = and David MacTAGGART
|publish_date = 28 April 2025
|description = In a turbulent medium, magnetic reconnection has two limiting domains
|image=Icon494.png}}

{{Nugget Badge
|title = Quasi-Periodic Pulsations in Ionospheric TEC and Flare EUV
|number = 493
|first_author = Aisling O'HARE
|publish_date = 21 April 2025
|description = The Earth's ionosphere reflects QPPs, with a small delay
|image=Icon493.png}}

{{Nugget Badge
|title = Metis observations of Alfvenic outflows driven by interchange reconnection in a pseudostreamer
|number = 492
|first_author = Paolo ROMANO and the Metis team
|publish_date = 7 April 2025
|description = Exactly as predicted by numerical simulations... a rare coup
|image=Icon492.png}}

{{Nugget Badge
|title = Solar Rollercoaster: looping-the-loop in the solar corona
|number = 491
|first_author = Mohamed NEDAL et al.
|publish_date = 31 March 2025
|description = Large-scale helical motion in the flare/CME SOL2024-05-14
|image=Icon491.png}}

{{Nugget Badge
|title = Proton Beam Energy Deposition as a Mechanism of Deep Photospheric Heating
|number = 490
|first_author = Samuel GRANOVSKY
|second_author = and Alexander KOSOVICHEV
|publish_date = 17 March 2025
|description = Evidence for proton beams in white-light flares
|image=Icon490.png}}

{{Nugget Badge
|title = New insights into the proton precipitation sites in solar flares
|number = 489
|first_author = Andrea Francesco BATTAGLIA
|second_author = and Säm KRUCKER
|publish_date = 17 February 2025
|description = There is no detectable difference in proton and electron foopoint locations after all
|image=Icon489.png}}

{{Nugget Badge
|title = Solar Gamma-Ray Evidence for a Distinct Population of MeV Flare-Accelerated Electrons
|number = 488
|first_author = Gerry SHARE
|second_author =
|publish_date = 10 February 2025
|description = Relativistic electrons in solar flares newly recognized as a distinct process
|image=Icon488.png}}

{{Nugget Badge
|title = From Chromospheric Evaporation to Coronal Rain: An Investigation of the Mass and Energy Cycle of a Flare‎
|number = 487
|first_author = Seray &Scedil;AHIN
|second_author = and Patrick ANTOLIN
|publish_date = 3 February 2025
|description = A first quantitative comparison of flare evaporation and coronal rain
|image=Icon487.png}}

{{Nugget Badge
|title = Energetic neutral atoms detected in the large solar energetic particle event of February 2022‎
|number = 486
|first_author = Christina COHEN
|second_author =
|publish_date = 20 January 2025
|description = Only the second direct observation of high-energy neutral atoms from the Sun
|image=Icon486.png}}

{{Nugget Badge
|title = Magnetic topology of quiet-Sun Ellerman bombs and associated ultraviolet brightenings‎
|number = 485
|first_author = Aditi BHATNAGAR
|second_author =
|publish_date = 6 January 2025
|description = Tiny "Ellerman Bombs" occur all across the solar surface, with differences
|image=Icon485.png}}

{{Nugget Badge
|title = Unveiling CME Dynamics: Rare Rotations of CMEs in the Heliosphere
|number = 484
|first_author = Sandeep KUMAR and
|second_author = Nandita SRIVASTAVA
|publish_date = 30 December 2024
|description = CMEs usually do not show additional rotation as they move though the heliosphere
|image=Icon484.png}}

{{Nugget Badge
|title = Spatial and Spectral Evolution of Microwave and X-Ray Sources During the Limb Flare SOL2023-02-05
|number = 483
|first_author = Yulia N. SHAMSUTDINOVA
|publish_date = 23 December 2024
|description = Rare microwave imaging spectroscopy of a hot-onset precursor event
|image=Icon483.png}}

{{Nugget Badge
|title = High-resolution observational analysis of flare ribbon fine structures
|number = 482
|first_author = Jonas THOEN FABER
|publish_date = 16 December 2024
|description = Spatially periodic fine structures in flare ribbons reveal current-sheet tearing
|image=Icon482.png}}

{{Nugget Badge
|title = Advection and super-diffusive expansion as the model of flare accelerated electron transport in type III solar radio bursts
|number = 481
|first_author = Eduard KONTAR
|publish_date = 9 December 2024
|description = Sturrock's dilemma resolved
|image=Icon481.png}}

{{Nugget Badge
|title = Faraday's Law in Solar Flares: A Cautionary Message
|number = 480
|first_author = Michael FARADAY
|publish_date = 2 December 2024
|description = We must not forget the global implications of Faraday's Law
|image=Icon480.png}}

{{Nugget Badge
|title = Remarkable NUV Spectrum of an M-star Megaflare
|number = 479
|first_author = Adam KOWALSKI
|publish_date = 25 November 2024
|description = Remarkable NUV spectra from an HST stellar flare
|image=Icon479.png}}

{{Nugget Badge
|title = Revised Point-Spread Functions of AIA and their effect on DEM analyses
|number = 478
|first_author =Stefan HOFMEISTER,
|second_author = Daniel Wolf SAVIN, and Michael HAHN
|publish_date = 18 November 2024
|description = Substantial revisions of the AIA point-response functions
|image=Icon478.png}}

{{Nugget Badge
|title = How much of the energy in flare-accelerated electrons reaches the chromosphere?
|number = 477
|first_author = Meriem ALAOUI
|second_author = and Gordon HOLMAN
|publish_date = 11 November 2024
|description = Keeping flare-accelerated electrons out of the chromosphere
|image=Icon477.png}}

{{Nugget Badge
|title = Spatially resolved plasma composition evolution in a solar flare
|number = 476
|first_author = Andy S. H. TO
|publish_date = 4 November 2024
|description = Reconnection outflow feeds abundance variations
|image=Icon476.png}}

{{Nugget Badge
|title = HOPE during high activity
|number = 475
|first_author = Hugh HUDSON
|second_author = and Alphonse STERLING
|publish_date = 28 October 2024
|description = Hot onsets appear even in the most active solar conditions
|image=Icon475.png}}

{{Nugget Badge
|title = Simulated heliospheric electron spectra show sensitivity to plasma properties of a source region in the flaring corona
|number = 474
|first_author = Ross PALLISTER
|second_author = and Natasha JEFFREY
|publish_date = 21 October 2024
|description = Getting closer to an understanding of how solar energetic particles "escape"
|image=Icon474.png}}

{{Nugget Badge
|title = An extremely complex active region with very strong non-neutralized electric currents
|number = 473
|first_author = Ioannis KONTOGIANNIS
|publish_date = 14 October 2024
|description = Large non-neutralized electric currents flow through the active-region corona
|image=Icon473.png}}

{{Nugget Badge
|title = An X9 flare and its huge crochet (SFE)
|number = 472
|first_author = Hugh HUDSON
|publish_date = 7 October 2024
|description = The geomagnetic effect (SFE/crochet) that will calibrate the Carrington flare
|image=Icon472.png}}

{{Nugget Badge
|title = All microflares that accelerate electrons to high energies are rooted in sunspots
|number = 471
|first_author = Andrea Francesco BATTAGLIA
|publish_date = 30 September 2024
|description = Microflares with hard X-ray spectra are a well-defined class, and invariably have one footpoint embedded in a sunspot
|image=Icon471.png}}

{{Nugget Badge
|title = The warm-target model and kappa distributions
|number = 470
|first_author = Yingjie LUO
|publish_date = 16 September 2024
|description = A self-consistent treatment of non-thermal electron spectra points to kappa distributions
|image=Icon470.png}}

{{Nugget Badge
|title = Is there HOPE for Hyder flares...
|number = 468
|first_author = Hugh HUDSON
|publish_date = 15 March 2024
|description = Filament eruptions/Hyder flares/disparitions brusques may all show HOPE
|image=Icon468.png}}

{{Nugget Badge
|title = Sun-as-a-star Analysis of the M8.7 Flare on 2022 October 2 Using H-alpha and EUV Spectra Taken by SMART/SDDI and SDO/EVE
|number = 467
|first_author = Takato OTSU
|publish_date = 19 February 2024
|description = Whole-Sun spectroscopic observations can readily detect ejecta
|image=Icon467.png}}

{{Nugget Badge
|title = Unexpected Asymmetry in GeV Emission
|number = 466
|first_author = Bruno ARSIOLI and Elena ORLANDO
|publish_date = 15 January 2024
|description = The high-energy solar gamma radiation shows inexplicable but fascinating properties
|image=Icon466.png}}

{{Nugget Badge
|title = When it rippled in one place and exploded in another
|number = 465
|first_author = Ivan ZIMOVETS
|publish_date = 25 December 2023
|description = Pulsations precede a flare, but seem unrelated
|image=Icon465.png}}

{{Nugget Badge
|title = Solar flares: evaporation and simulation‎
|number = 464
|first_author = Malcolm DRUETT
|publish_date = 18 December 2023
|description = Fitting beam electrons into multi-dimensional models
|image=Icon464.png}}

{{Nugget Badge
|title = Pre-impulsive and Impulsive Phases of the March 28, 2022 Sub-Terahertz Flare
|number = 463
|first_author = Galina G. MOTORINA
|publish_date = 11 December 2023
|description = A flare with an increasing sub-THz spectrum and sub-THZ precursor information
|image=Icon463.png}}

{{Nugget Badge
|title = Coronal Bright Points
|number = 462
|first_author = Daniel NÓBREGA-SIVERIO
|publish_date = 27 November 2023
|description = Bright EUV rowel-like structures can result from null-point reconnection
|image=Icon462.png}}

{{Nugget Badge
|title = Aurora-like Radio Emission from a Sunspot
|number = 461
|first_author = Sijie YU
|publish_date = 20 November 2023
|description = Maser action above a sunspot
|image=Icon461.png}}

{{Nugget Badge
|title = Search for a Flare Anticipation Index (FAI)
|number = 460
|first_author = Hugh HUDSON
|second_author = and Jim McTiernan
|publish_date = 13 November 2023
|description = Quantifying flare precursors on a few-minute time scale
|image=Icon460.png}}

{{Nugget Badge
|title = Bouncing motions of fast electrons using Nobeyama Radioheliograph
|number = 459
|first_author = Keitarou MATSUMOTO
|publish_date = 6 November 2023
|description = Solar evidence for conservation of second adiabatic invariant in particle motion
|image=Icon459.png}}

{{Nugget Badge
|title = Impact of nanoflare heating in the lower solar atmosphere
|number = 458
|first_author = Helle BAKKE
|publish_date = 30 October 2023
|description = The behavior of nanoflare fast electrons in Bifrost models
|image=Icon458.png}}

{{Nugget Badge
|title = Precise timing of flare footpoint sources from mid-infrared observations‎
|number = 457
|first_author = Paulo SIMÕES et al.
|publish_date = 23 October 2023
|description = Mid-IR observations at high spatial and high temporal resolution: Conjugacy
|image=Icon457.png}}

{{Nugget Badge
|title = The Greatest GOES Flares‎
|number = 456
|first_author = Hugh HUDSON
|second_author = and Ed CLIVER
|publish_date = 25 September 2023
|description = The greatest GOES events, re-analyzed, fall short of expectations
|image=Icon456.png}}

{{Nugget Badge
|title = Introducing SunSketcher
|number = 455
|first_author = Hugh HUDSON
|second_author = and Gordon EMSLIE
|publish_date = 11 September 2023
|description = Galloping towards roundup in the 2024 total solar eclipse
|image=Icon455.png}}

{{Nugget Badge
|title = TeV Gamma rays from the Quiescent Sun
|number = 454
|first_author = Mehr Un NISA
|second_author = and John BEACOM
|publish_date = 21 August 2023
|description = Solar photons at unprecedented high energies
|image=Icon454.png}}

{{Nugget Badge
|title = Temporal and Spatial Characteristics of Hard X-Ray Sources in Flare Model with Vertical Current Sheet
|number = 453
|first_author = Alexander SHABALIN, Eugenia OVCHINNIKOVA,
|second_author = and Yuri CHARIKOV
|publish_date = 7 August 2023
|description = Modeling betatron acceleration in current-sheet development.
|image=Icon453.png}}

{{Nugget Badge
|title = Spatial Distribution of Magnetic Reconnection Rate in an M6.5 Solar Flare
|number = 452
|first_author = Ju JING
|publish_date = 12 June 2023
|description = Linking hard X-rays to high-resolution images that show reconnection rates.
|image=Icon452.png}}

{{Nugget Badge
|title = Statistical study of Type III bursts and associated HXR emissions
|number = 451
|first_author = Nicole VILMER and Tomin JAMES
|publish_date = 29 May 2023
|description = Linking electron populations escaping from the Sun with those that RHESSI detects.
|image=Icon451.png}}

{{Nugget Badge
|title = Solar flare hard X-rays from the anchor points of an eruptive filament
|number = 450
|first_author = Muriel STIEFEL
|publish_date = 15 May 2023
|description = A rare "four-ribbon" flare has been detected in hard X-rays.
|image=Icon450.png}}

{{Nugget Badge
|title = Did a Solar Flare Accelerate all the Ambient Electrons in the Coronal Acceleration Region?...
|number = 449
|first_author = Gordon EMSLIE, Eduard KONTAR,
|second_author = Galina MOTORINA, and Brian DENNIS
|publish_date = 1 May 2023
|description = Considering SOL2017-09-10, probably not.
|image=Icon449.png}}

{{Nugget Badge
|title = Diagnostics of Spatially-Extended Turbulent Acceleration and Transport
|number = 448
|first_author = Morgan STORES
|publish_date = 24 April 2023
|description = Drilling down into the detailed structure of solar-flare energy release by including turbulence with particle acceleration.
|image=Icon448.png}}

{{Nugget Badge
|title = RHESSI's Re-entry
|number = 447
|first_author = Pascal SAINT-HILAIRE and
|second_author = Hugh HUDSON
|publish_date = 17 April 2023
|description = The final demise of RHESSI is this week
|image=Icon447.png}}

{{Nugget Badge
|title = A Glasgow geomagnetic observation of a solar flare
|number = 446
|first_author = Hugh HUDSON, John MALONE-LEIGH,
|second_author = Graham WOAN, and Chris OSBORNE
|publish_date = 13 March 2023
|description = Irish and Scottish geomagnetic observatories see a crochet much like that of the Carrington event
|image=Icon_446.png}}

{{{Nugget Badge
|title = Particle Acceleration in Two Coronal Jets
|number = 445
|first_author = Yixian ZHANG
|publish_date = 27 February 2023
|description = Coronal jets with hard X-ray sources at disjoint locations
|image=Icon445.png}}

{{Nugget Badge
|title = The Curious First Sunquake of Solar Cycle 25‎
|number = 444
|first_author = Alexander KOSOVICHEV
|publish_date = 13 February 2023
|description = A double whammy: two distinct sunquakes from SOL2022-05-10.
|image=Icon444.png}}

{{Nugget Badge
|title = Hard X-ray Pulsations via Gaussian Decomposition
|number = 443
|first_author = Hannah COLLIER and Laura HAYES
|publish_date = 30 January 2023
|description = Flare hard X-ray time variations decomposed objectively
|image=Icon443.png}}

{{Nugget Badge
|title = A possible coronal magnetic flare precursor
|number = 442
|first_author = Enrico LANDI
|publish_date = 16 January 2023
|description = Novel measurements of the coronal magnetic field may help with flare prediction
|image=Icon442.png}}

{{Nugget Badge
|title = A slow HOPE with microwave context
|number = 441
|first_author = Hugh HUDSON
|publish_date = 12 December 2022
|description = A new microwave facility at Chashan Observatory, and a prototypical HOPE
|image=Icon441.png}}

{{Nugget Badge
|title = Rapid variations of Si IV spectra in a flare observed by IRIS at a sub-second cadence
|number = 440
|first_author = Juraj LÖRINČÍK
|publish_date = 14 November 2022
|description = Transition-region lines in a flare have a Doppler component revealing quasi-periodic pulsations
|image=Icon440.png}}

{{Nugget Badge
|title = A Significant Sudden Ionospheric Disturbance Associated with a Massive Gamma-ray Burst
|number = 439
|first_author = Laura HAYES and Peter GALLAGHER
|publish_date = 31 October 2022
|description = A first SID observed in broad daylight, from a source far far away
|image=Icon439.png}}

{{Nugget Badge
|title = Effects of Coronal Structures on the Dynamics of the Global Coronal Wave of SOL2017-09-10‎
|number = 438
|first_author = Huidong HU, Ying D. LIU, and Bei ZHU
|publish_date = 17 October 2022
|description = The amazing global coronal wave of SOL2017-09-10 wrapped around the whole Sun, and displayed transmission and reflection at both polar coronal holes
|image=Icon438.png}}

{{Nugget Badge
|title = KW-Sun: The Konus-Wind Solar Flare Database in Hard X-Ray and Soft Gamma-Ray Ranges
|number = 437
|first_author = Alexandra LYSENKO
|publish_date = 26 September 2022
|description = An unrivaled hard X-ray and gamma-ray database is entering its third activity maximum
|image=Icon437.png}}

{{Nugget Badge
|title = First Detection of Kink Oscillations with Solar Orbiter
|number = 436
|first_author = Sihui ZHONG et al.
|publish_date = 19 September 2022
|description = SolO sees coronal oscillations as well as AIA can, and even better
|image=Icon436.png}}

{{Nugget Badge
|title = Energetic Neutral Hydrogen from Large Solar Flares
|number = 435
|first_author = Glenn MASON
|publish_date = 6 September 2022
|description = A rediscovered data treasury reveals the occurrence of many flare/CME events producing solar high-energy neutral atoms
|image=Icon435.png}}

{{Nugget Badge
|title = Fifty-year Anniversary of the First Detection of Gamma rays from a Solar Flare
|number = 434
|first_author = Jim Ryan,
|second_author = Brian Dennis, and Phil Dunphy
|publish_date = 8 August 2022
|description = The rich astrophysics of gamma-ray astronomy began with solar observations fifty years ago
|image=Icon434.png}}

{{Nugget Badge
|title = Fast Prograde Flows in Solar Active Regions
|number = 433
|first_author = Hugh HUDSON
|publish_date = 25 July 2022
|description = Unexpected, unpredicted, and not modeled yet - weird flows in hot active-region loops
|image=Icon433.png}}

{{Nugget Badge
|title = Undetected Minority-polarity Flux, Moss, and Coronal Heating
|number = 432
|first_author = Yi-Ming WANG
|publish_date = 11 July 2022
|description = There's plenty of room in "unipolar" active regions for both polarities, and there is good evidence for them
|image=Icon432.png}}

{{Nugget Badge
|title = Thermal/Nonthermal with MinXSS and RHESSI
|number = 431
|first_author = Shunsaku NAGASAWA
|publish_date = 13 June 2022
|description = Time-domain studies of improved X-ray spectra reveal a "super-hot' component
|image=Icon431.png}}

{{Nugget Badge
|title = Sun-as-a-star spectroscopic observations of the line-of-sight velocity of a solar eruption on October 28, 2021
|number = 430
|first_author = Yu XU
|second_author = and Hui TIAN
|publish_date = 30 May 2022
|description = The observation of the full 3d velocity of a CME, for an anniversary event
|image=Icon430.png}}

{{Nugget Badge
|title = Carl Størmer
|number = 429
|first_author = Hugh HUDSON
|second_author = and Lyndsay FLETCHER
|publish_date = 15 April 2022
|description = Størmer and the theory of trapping in loops
|image=Icon429.png}}

{{Nugget Badge
|title = Solar Hard X-rays with Insight
|number = 428
|first_author = Wei WANG
|second_author = and Ping ZHANG
|publish_date = 21 March 2022
|description = A spectacular limb flare introduces Insight/HXMT, a new observational resource
|image=Icon428.png}}

{{Nugget Badge
|title = Probing chromospheric current sheets using SST and ALMA co-observations
|number = 427
|first_author = João da SILVA SANTOS
|publish_date = 21 February 2022
|description = Emerging magnetic flux appears in ALMA images reflecting coronal current sheets
|image=Icon427.png}}

{{Nugget Badge
|title = A demonstration of STIX hard X-ray imaging spectroscopy capabilities for an X-class flare (SOL2021-10-28)
|number = 426
|first_author = Andrea BATTAGLIA, Hannah COLLIER,
|second_author = and Säm KRUCKER
|publish_date = 7 February 2022
|description = STIX imaging of an X-class flare marks its success
|image=Icon426.png}}

{{Nugget Badge
|title = A solar flare driven by thermal conduction observed in mid-infrared
|number = 425
|first_author = Guillermo GIMÉNEZ de CASTRO
|publish_date = 24 January 2022
|description = Strong 10-micron emission from a GOES C2 flare suggests conductive heating
|image=Icon425.png}}

{{Nugget Badge
|title = Disk Occultation of a Lopsided Sun‎
|number = 424
|first_author = Hugh HUDSON,
|second_author = Stephen WHITE and Säm KRUCKER
|publish_date = 10 January 2022
|description = Observing a spotless Sun can enable observations of the faint corona.
|image=Icon424.png}}

{{Nugget Badge
|title = Resolving two distinct thermal X-ray components in a compound solar flare
|number = 423
|first_author = Zhenjun ZHOU
|second_author = and Rui LIU
|publish_date = 28 December 2021
|description = Superhot coronal sources may be independent loop systems
|image=Icon423.png}}

{{Nugget Badge
|title = Bridging solar flares to coronal mass ejections
|number = 422
|first_author = Markus ASCHWANDEN
|publish_date = 14 December 2021
|description = The Neupert effect allows us to trace coronal mass ejections seamlessly
|image=Icon422.png}}

{{Nugget Badge
|title = The Jakimiec Diagnostic Diagram
|number = 421
|first_author = Hugh HUDSON
|publish_date = 29 November 2021
|description = The joint variation of GOES temperature and emission measure discloses new features via an old tool
|image=Icon421.png}}

{{Nugget Badge
|title = First look at ALMA/HInode/IRIS microflares
|number = 420
|first_author = Toshifumi SHIMIZU
|second_author = et al.
|publish_date = 8 November 2021
|description = High-resolution ALMA and multiwavelength observations of microflaring
|image=Icon420.png}}

{{Nugget Badge
|title = Thomson scattering near sunspots
|number = 419
|first_author = Pascal Saint-Hilaire
|second_author = et al.
|publish_date = 25 October 2021
|description = Completing the modeling of low-coronal Thomson polarimetry
|image=Icon419.png}}

{{Nugget Badge
|title = A Non-PFSS Global Coronal Model
|number = 418
|first_author = Oliver RICE
|second_author = and Anthony YEATES
|publish_date = 11 October 2021
|description = Modeling as convenient as PFSS but much more realistic
|image=Icon418.png}}

{{Nugget Badge
|title = Manifold Nonthermality
|number = 417
|first_author = Marina BATTAGLIA
|second_author = et al.
|publish_date = 27 September 2021
|description = Even weak flares involve multiple sites of non thermal activity
|image=Icon417.png}}

{{Nugget Badge
|title = X-Rays from a Type I Radio Burst
|number = 416
|first_author = R. RAMESH
|publish_date = 20 September 2021
|description = A first identification of type I radio emission with hot plasma
|image=Icon416.png}}

{{Nugget Badge
|title = Do Hot Onsets Predict Flare Magnitudes?
|number = 415
|first_author = Hugh HUDSON
|publish_date = 30 August 2021
|description = Maybe we can tell how big a flare is going to be from its initial development...
|image=Icon415.png}}

{{Nugget Badge
|title = Confined or Eruptive?
|number = 414
|first_author = Ting LI et al.
|publish_date = 16 August 2021
|description = Increased magnetic flux reduces CME eruptivity
|image=Icon414.png}}

{{Nugget Badge
|title = Impulsive and Gradual Eruptive Gamma Flares and Associated CMEs
|number = 413
|first_author = Alexey STRUMINSKY,
|second_author = Irina GRIGORIEVA and Andrei SADOVSKI
|publish_date = 19 July 2021
|description = Extreme behavior of flare/CME events explained by environment
|image=Icon373.png}}

{{Nugget Badge
|title = The Morphology of Flare Time Profiles
|number = 412
|first_author = Larisa KASHAPOVA
|second_author = et al.
|publish_date = 12 July 2021
|description = Systematic comparison of solar and stellar flaring time profiles
|image=Icon412.png}}

{{Nugget Badge
|title = Flare Pulsation and the Heliosphere
|number = 411
|first_author = Brendan CLARKE
|second_author = et al.
|publish_date = 5 July 2021
|description = Flare pulsations link closely to the distant heliosphere
|image=Icon411.png}}

{{Nugget Badge
|title = STIX, the Hard X-Ray Telescope on board Solar Orbiter
|number = 410
|first_author = Andrea Francesco BATTAGLIA
|second_author = and Säm KRUCKER
|publish_date = 28 June 2021
|description = STIX is operational and producing great data
|image=Icon410.png}}

{{Nugget Badge
|title = Nonequilibrium Ionization of Flare Plasma Observed by Hinode/EIS
|number = 409
|first_author = Shinsuke IMADA
|second_author =
|publish_date = 14 June 2021
|description = Evidence for non-equilibrium ionization in the current sheet of SOL2017-09-10
|image=Icon409.png}}

{{Nugget Badge
|title = Effects of Flares on Solar p-modes
|number = 408
|first_author = Maria-Cristina RABELLO SOARES
|second_author = and Frederic BAUDIN
|publish_date = 26 April 2021
|description = No detectable p-mode amplitude changes due to solar flares
|image=Icon408.png}}

{{Nugget Badge
|title = Subsecond Spikes in Solar Flare X-ray Flux as Seen by Fermi GBM
|number = 407
|first_author =Trevor KNUTH
|second_author = and Lindsay GLESENER
|publish_date = 19 April 2021
|description = A new analysis technique pushes hard X-ray time scales to 0.1 sec or faster
|image=Icon407.png}}

{{Nugget Badge
|title = Negative He 10830 Flare Ribbons and Non-thermal Electrons
|number = 406
|first_author = Graham KERR
|second_author =
|publish_date = 12 April 2021
|description = A 1D radiation hydrodynamics model can explain the dark leading edges of He I flare ribbons
|image=Icon406.png}}

{{Nugget Badge
|title = Tracing the sources of gradual solar energetic particle events
|number = 405
|first_author = David H. BROOKS
|second_author = and Stephanie L. YARDLEY
|publish_date = 29 March 2021
|description = Chemical abundances in SEPs suggest an origin in flare-related moss regions
|image=Icon405.png}}

{{Nugget Badge
|title = The Superflare SOL2017-09-06: from submm to mid-IR
|number = 404
|first_author = Guillermo (Guigue) GIMÉNEZ DE CASTRO
|second_author =
|publish_date = 15 March 2021
|description = Glimpsing the "missing decades" of the flare emission spectrum
|image=Icon404.png}}

{{Nugget Badge
|title = The Neupert Effect Revisited
|number = 403
|first_author = Jiong QIU
|second_author =
|publish_date = 8 March 2021
|description = Two time scales for heating individual flare strands
|image=Icon403.png}}

{{Nugget Badge
|title = FLUKA as a tool for interpreting flare gamma-rays
|number = 402
|first_author = Alec MACKINNON
|second_author =
|publish_date = 1 March 2021
|description = The nuclear physics of solar flares captured in a detailed model
|image=Icon402.png}}

{{Nugget Badge
|title = A Collective Study of 11 NuSTAR Microflares
|number = 401
|first_author = Jessie DUNCAN and
|second_author = Lindsay GLESENER
|publish_date = 22 February 2021
|description = Swarms of NuSTAR micro flares
|image=Icon401.png}}

{{{{Nugget Badge
|title = A Solar FRB
|number = 400
|first_author = Dale GARY and
|second_author = Hugh HUDSON
|publish_date = 15 February 2021
|description = A new frontier in the solar time domain
|image=Icon400.png}}

{{Nugget Badge
|title = Richard Schwartz
|number = 399
|first_author = Brian DENNIS and
|second_author = Hugh HUDSON
|publish_date = 25 January 2021
|description = Remembering a friend and colleague
|image=Icon399.jpg}}

{{Nugget Badge
|title = Observing Solar Flare X-ray Polarization with Prospective CubeSat Missions
|number = 398
|first_author = Natasha JEFFREY
|publish_date = 4 January 2021
|description = The polarization of the solar X-ray spectrum generally remains to be observed
|image=Icon398.png}}

{{Nugget Badge
|title = Solar effects in the local interstellar medium
|number = 397
|first_author = Don GURNETT and
|second_author = Hugh HUDSON
|publish_date = 14 December 2020
|description = Relativistic particle events observed _in situ_ in the interstellar medium
|image=Icon397.png}}

{{Nugget Badge
|title = Investigation of Small-Scale Energy Releases in Hard X-rays with FOXSI
|number = 396
|first_author = Subramania ATHIRAY and
|second_author = Juliana VIEVERING
|publish_date = 7 December 2020
|description = Hard X-rays and high temperatures from the feeblest microflares
|image=Icon396.png}}

{{Nugget Badge
|title = What drives impulsive coronal heating?
|number = 395
|first_author = Pradeep CHITTA
|second_author = et al.
|publish_date = 30 November 2020
|description = Impulsive footpoint emissions suggest magnetic reconnection in the chromosphere
|image=Icon395.png}}

{{Nugget Badge
|title = Probing the solar coronal heating function with slow magnetoacoustic waves
|number = 394
|first_author = Dmitrii KOLOTKOV
|second_author = et al.
|publish_date = 16 November 2020
|description = Coronal heating models meet damped slow magnetoacoustic waves
|image=Icon394.png}}

{{Nugget Badge
|title = Self-Consistent Flare Model
|number = 393
|first_author = Wenzhi RUAN
|second_author = and Rony KEPPENS
|publish_date = 2 November 2020
|description = Energy transport by fast particles made self-consistent with MHD flare modeling
|image=Icon393.png}}

{{Nugget Badge
|title = Hot Flare Onsets
|number = 392
|first_author = Hugh HUDSON
|second_author = et al.
|publish_date = 26 October 2020
|description = The initial soft X-ray temperatures of solar flares tend to be in the 10-15 MK range
|image=Icon392.png}}

{{Nugget Badge
|title = Electric Current Neutralization and Eruption
|number = 391
|first_author = Ellis AVALLONE
|second_author = and Xudong SUN
|publish_date = 19 October 2020
|description = Coronal currents without neutralizing return currents appear to
|image=Icon391.png}}

{{Nugget Badge
|title = Prediction of Solar Cycle 25
|number = 390
|first_author = Leif SVALGAARD
|second_author =
|publish_date = 5 October 2020
|description = Now we know how big the next solar maximum will be
|image=Icon390.png}}

{{Nugget Badge
|title = Flare/CME Cartoon Archive
|number = 389
|first_author = Hugh HUDSON
|second_author =
|publish_date = 27 September 2020
|description = A new edition of the Flare/CME archive, nearly a half kilotoon now
|image=Icon389.png}}

{{Nugget Badge
|title = Submerged Flare Acoustic Sources
|number = 388
|first_author = Juan Camilo BUITRAGO CASAS
|second_author = and Angel MARTÍNEZ
|publish_date = 13 September 2020
|description = Flare acoustic radiation emanates from a source _inside_ the Sun
|image=Icon388.png}}

{{Nugget Badge
|title = Circular Ribbon Flare at Microwaves
|number = 387
|first_author = Jeongwoo LEE
|second_author =
|publish_date = 31 August 2020
|description = Breakout reconnection reveals itself via microwave polarization measurements.
|image=Icon387.png}}

{{Nugget Badge
|title = Relation of Non-neutralized electric currents and the activity in active regions
|number = 386
|first_author = P. VEMAREDDY
|second_author =
|publish_date = 24 August 2020
|description = Non-neutralized coronal current systems contribute to CME eruptions
|image=Icon386.png}}

{{Nugget Badge
|title = White-light emission and photospheric magnetic field changes in flares
|number = 385
|first_author = J. Sebastián CASTELLANOS DURÁN
|second_author = and Lucia KLEINT
|publish_date = 17 August 2020
|description = There are strong correlations between white-light flare emissions and line-of-sight magnetic field changes
|image=Icon385.png}}

{{Nugget Badge
|title = Sunspot Differential Rotation in an X-class Flare
|number = 384
|first_author = Richard GRIMES,
|second_author = Balázs PINTÉR and Huw MORGAN
|publish_date = 10 August 2020
|description = Observations suggesting how the coronal tail can wag the photospheric dog
|image=Icon384.png}}

{{Nugget Badge
|title = Energy Partitioning in a Nonthermally Dominated Two-loop Solar Flare
|number = 383
|first_author = Galina MOTORINA
|second_author = et al.
|publish_date = 3 August 2020
|description = Modeling the propagation of energy via GX Simulator in an early-impulsive flare
|image=Icon383.png}}

{{Nugget Badge
|title = SOL2013-11-10 Eruptive Circular-ribbon Flare with Extended Remote Brightenings
|number = 382
|first_author = Chang LIU
|second_author = et al.
|publish_date = 31 July 2020
|description = A circular-ribbon event can launch an eruption by breaking through its separatrix dome
|image=Icon382.png}}

{{Nugget Badge
|title = Extreme-Ultraviolet Late Phase of Solar Flares
|number = 381
|first_author = Rui LIU
|second_author =
|publish_date = 22 June 2020
|description = Both arcade and circular-ribbon flares may sometimes spawn EUV late phase emission
|image=Icon381.png}}

{{Nugget Badge
|title = Energy transport by accelerated particles in the quiet solar atmosphere
|number = 380
|first_author = Lars FROGNER,
|second_author = Boris GUDIKSEN and Helle BAKKE
|publish_date = 15 June 2020
|description = A first study of non-thermal particles integrated into an MHD simulation of the solar atmosphere
|image=Icon380.png}}

{{Nugget Badge
|title = Quasi-periodic pulsations as indicators of oscillatory processes in solar flares
|number = 379
|first_author = Elena KUPRIYANOVA
|second_author = et al.
|publish_date = 11 May 2020
|description = Many, many QPPs
|image=Icon379.png}}

{{Nugget Badge
|title = Rejuvenating Solar Flare Termination Shocks as Particle Accelerators
|number = 378
|first_author = Bin CHEN
|second_author =
|publish_date = 4 May 2020
|description = At last, clear evidence for a long-predicted phenomenon
|image=Icon378.png}}

{{Nugget Badge
|title = Broad symmetrical Doppler-shifted Fe XXI line profiles
|number = 377
|first_author = Vanessa POLITO
|second_author =
|publish_date = 20 April 2020
|description = It is difficult to explain "evaporation" line profiles by superposition of unresolved flows
|image=Icon377.png}}

{{Nugget Badge
|title = Phenomena in the unusually long pre-impulsive phase of SOL2011-06-07
|number = 376
|first_author = Marian KARLICKÝ,
|second_author = Jana KA&Scaron;PAROVÁ, and Robert SYCH
|publish_date = 13 April 2020
|description = A massive and slowly-rising filament eruption reveals important new signatures of the physics
|image=Icon376.png}}

{{Nugget Badge
|title = Evidence for a Coronal Shock Wave Origin for Relativistic Protons Producing Solar Gamma-Rays and Observed by Neutron Monitors at Earth‎
|number = 375
|first_author = Athanasios KOULOUMVAKOS
|second_author = and Gerry SHARE
|publish_date = 6 April 2020
|description = Successful modeling of prolonged solar gamma-ray emissions and terrestrial ground-level cosmic-ray events
|image=Icon375.png}}

{{Nugget Badge
|title = Using overlappogram data to find hot flare plasma
|number = 374
|first_author = Louise HARRA
|
|publish_date = 23 March 2020
|description = Imaging Fe XXIV at high resolution with the EIS slot data
|image=Icon374.png}}

{{Nugget Badge
|title = SOL2017-09-04 (M5.5) 2017 as a Source of Relativistic Electrons and Protons
|number = 373
|first_author = Alexei STRUMINSKII
| (see text)
|publish_date = 16 March 2020
|description = Flare-accelerated particles, rather than SEPs, energize sustained gamma-ray emission
|image=Icon373.png}}

{{Nugget Badge
|title = Heating of the solar photosphere during a white-light flare‎
|number = 372
|first_author = Jan JURČÁK
| (see text)
|publish_date = 2 March 2020
|description = The best-ever spectrum of the flare photosphere
|image=Icon372.png}}

{{Nugget Badge
|title = A Hot Cusp-Shaped Confined Solar Flare
|number = 371
|first_author = Aaron HERNANDEZ-PEREZ
|publish_date = 24 February 2020
|description = A flare may have a prominent hot cusp with the help of any eruption
|image=Icon371.png}}

{{Nugget Badge
|title = The Temporal and Spatial Extension of Gamma-ray Emission from the Sun
|number = 370
|first_author = Nat GOPALSWAMY
|publish_date = 17 February 2020
|description = Sustained solar γ-rays and solar cosmic rays
|image=Icon370.ng.png}}

{{Nugget Badge
|title = A PSP Perihelion
|number = 369
|first_author = Jessie DUNCAN
|second_author = and Hugh Hudson
|publish_date = 20 January 2020
|description = The Parker Solar Probe enters its fourth perihelion already. Now
|image=Icon369.png}}

{{Nugget Badge
|title = Remembering John Brown
|number = 368
|first_author = Alec MacKINNON
|second_author =
|publish_date = 13 January 2020
|description = John passed away unexpectedly on 16 November 2019
|image=Icon368.png}}

{{Nugget Badge
|title = A Global Survey of EUV Coronal Power Spectra
|number = 367
|first_author = Karl Battams
|second_author =
|publish_date = 30 December 2019
|description = Time-series parameter maps of imaged power spectra from an AIA pipeline
|image=Icon367.png}}

{{Nugget Badge
|title = Cosmic Rays over the Rainbow Bridge
|number = 366
|first_author = Hugh Hudson
|second_author = Alec MacKinnon
|publish_date = 16 December 2019
|description = Cosmic rays approach the Sun
|image=Icon366.png}}

{{Nugget Badge
|title = Spectropolarimetric Insight into Plasma-Sheet Dynamics of a Solar Flare
|number = 365
|first_author = Ryan French
|second_author =
|publish_date = 9 December 2019
|description = CoMP polarization patterns in SOL2017-09-10 are amazing
|image=Icon365.png}}

{{Nugget Badge
|title = Lorentz Force Evolution Reveals the Energy Build-up Processes during Recurrent Eruptive Solar Flares‎
|number = 364
|first_author = Ranadeep Sarkar,
|second_author = Nandita Srivastava and Astrid Veronig
|publish_date = 18 November 2019
|description = The net Lorentz force clearly exhibits a build-up and release pattern
|image=Icon364.png}}

{{Nugget Badge
|title = Flare waiting times depend on their magnitudes
|number = 363
|first_author = Hugh Hudson
|second_author =
|publish_date = 11 November 2019
|description = Surprising new evidence for the flare build-up and release process
|image=Icon363.png}}

{{Nugget Badge
|title = Can magnetic reconnection cause solar rainstorms?‎
|number = 362
|first_author = Petra Kohutova
|second_author =
|publish_date = 4 November 2019
|description = Impulsive coronal heating resulting from reconnection can trigger coronal rain
|image=Icon362.png}}

{{Nugget Badge
|title = Non-radial jets on the edges of active regions
|number = 361
|first_author = Peter Wyper
|second_author =
|publish_date = 14 October 2019
|description = The very common jet structures we see can naturally combine twist and breakout
|image=Icon361.png}}

{{Nugget Badge
|title = Searching SOLfully within the Nuggets
|number = 360
|first_author = Hugh Hudson
|second_author =
|publish_date = 7 October 2019
|description = The IAU target identifier works well for finding items about a particular event
|image=Icon360.png}}

{{Nugget Badge
|title = Submillimeter Radiation as the Thermal Component of the Neupert Effect
|number = 359
|first_author = Guillermo Giménez de Castro
|second_author =
|publish_date = 31 September 2019
|description = Flare radiation at the highest frequencies can be bremsstrahlung
|image=Icon359.png}}

{{Nugget Badge
|title = The "Last Best" Flares
|number = 358
|first_author = Hugh Hudson,
|second_author = Ed Cliver, and Brian Dennis
|publish_date = 24 September 2019
|description = Major flares tend to happen at the very ends of sunspot cycles
|image=Icon358.png}}

{{Nugget Badge
|title = Dynamic Processes of the Moreton Wave on 2014 March 29‎
|number = 357
|first_author = Denis Cabezas
|second_author = and the FMT team
|publish_date = 16 September 2019
|description = A beautiful Moreton wave excited by the best-observed flare ever
|image=Icon357.png}}

{{Nugget Badge
|title = EVE-RHESSI DEM Models and the Low-energy Cutoff for Nonthermal Electrons
|number = 356
|first_author = Jim McTiernan
|second_author =
|publish_date = 9 September 2019
|description = Characterizing flare temperature distributions helps to define the non-thermal energy release
|image=Icon356.png}}

{{Nugget Badge
|title = Stealth Coronal Mass Ejections from Active Regions
|number = 355
|first_author = Jennifer O'Kane
|second_author =
|publish_date = 26 August 2019
|description = Perhaps just feeble versions of the same magnetic disease...
|image=Icon355.png}}

{{Nugget Badge
|title = Do Kepler Superflare Stars Really Include Slowly Rotating Sun-like Stars?‎
|number = 354
|first_author = Yuta NOTSU
|second_author =
|publish_date = 15 July 2019
|description = Kepler superflares hint at solar superflares
|image=Icon354.png}}

{{Nugget Badge
|title = Localized Microwave and EUV Bright Structures in an Eruptive Prominence
|number = 353
|first_author = Jing HUANG
|second_author =
|publish_date = 22 June 2019
|description = Detailed correlations between EUV and microwaves in prominence fine structures
|image=Icon353.png}}

{{Nugget Badge
|title = Broken-up hard X-ray spectra found for a loop-top source during a solar limb flare
|number = 352
|first_author = Hao NING,
|second_author = Yao CHEN and Jeongwoo LEE
|publish_date = 16 June 2019
|description = SOL2017-09-10 coronal hard X-ray sources
|image=Icon352.png}}

{{Nugget Badge
|title = The Cosmic-Ray Shadow and Coronal Magnetism
|number = 351
|first_author = Frederik Tenholt
|second_author =
|publish_date = 27 May 2019
|description = The coronal magnetic field measured in Antarctica
|image=Icon351.png}}

{{Nugget Badge
|title = Kristian Birkeland
|number = 350
|first_author = Hugh HUDSON
|second_author = and Lyndsay FLETCHER
|publish_date = 6 May 2019
|description = Space weather a century ago: Kristian Birkeland
|image=Icon350.png}}

{{Nugget Badge
|title = Warm UV loops heated by small-scale cancellation events
|number = 349
|first_author = Seray ŞAHIN
|second_author = and Vasyl YURCHYSHYN
|publish_date = 22 April 2019
|description = Precisely locating the footpoints of warm coronal loops helps identify their source(s) of excitation
|image=Icon349.png}}

{{Nugget Badge
|title = Multiple Regions of Shock-accelerated Particles during a Solar Coronal Mass Ejection
|number = 348
|first_author = Diana MOROSAN
|second_author =
|publish_date = 1 April 2019
|description = LOFAR identifies herringbone sources within the flank of the SOL2017-09-10 shock - no joke
|image=Icon348.png}}

{{Nugget Badge
|title = Persistent Quasi-Periodic Pulsations Detected During the Large X8.2 Solar Flare
|number = 347
|first_author = Laura HAYES
|second_author = and Peter GALLAGHER
|publish_date = 25 March 2019
|description = The most beautiful flare has the most beautiful pulsations
|image=Icon347.png}}

{{Nugget Badge
|title = Is the coronal magnetic field braiding?
|number = 346
|first_author = Markus ASCHWANDEN
|second_author =
|publish_date = 11 March 2019
|description = This iconic cartoon does not relate well to the observations
|image=Icon346.png}}

{{Nugget Badge
|title = An energetic pre-flare: electron distributions in magnetic reconnection outflows
|number = 345
|first_author = Marina BATTAGLIA,
|second_author = Eduard KONTAR and Galina MOTORINA
|publish_date = 18 February 2019
|description = Assessing energy partition in a pre-impulsive flare development
|image=Icon345.png}}

{{Nugget Badge
|title = Linear Polarization in H-alpha Flares
|number = 344
|first_author = Tomoko KAWATE
|second_author = and Yoichiro HANAOKA
|publish_date = 4 February 2019
|description = H-alpha polarization is rarely observable but, in once case, very suggestive
|image=Icon344.png}}

{{Nugget Badge
|title = Short-Period Waves
|number = 343
|first_author = Sijie YU
|second_author = and Bin CHEN
|publish_date = 21 January 2019
|description = New decimetric imaging spectroscopy suggests Alfvénic energy transport in flares
|image=Icon343.png}}

{{Nugget Badge
|title = The Interesting RHESSI/SAS Archive
|number = 342
|first_author = Hugh HUDSON
|second_author = and Martin FIVIAN
|publish_date = 8 January 2019
|description = The full mission database shows RHESSI to have been very stable geometrically
|image=Icon342.png}}

{{Nugget Badge
|title = Homologous White Light Solar Flares‎
|number = 341
|first_author = Paolo ROMANO
|second_author = and Abouazza ELMHAMDI
|publish_date = 31 December 2018
|description = Homologous white-light flares, in rapid succession, and coronal null points
|image=Icon341.png}}

{{Nugget Badge
|title = The flight of FOXSI-3
|number = 340
|first_author = Lindsay GLESENER
|second_author = and Noriyuki NARUKAGE
|publish_date = 10 December 2018
|description = Single-photon counting and direct focusing across hard and soft energies
|image=Icon340.png}}

{{Nugget Badge
|title = Stellar Flares and Starspots
|number = 339
|first_author = Lauren DOYLE
|second_author =
|publish_date = 3 December 2018
|description = Stellar flares don't spatially match their starspots
|image=Icon339.png}}

{{Nugget Badge
|title = Neutron Production in Solar Flares
|number = 338
|first_author = Ron MURPHY
|second_author = and Gerry SHARE
|publish_date = 26 November 2018
|description = Neutron astronomy helps us understand solar flares
|image=Icon338.png}}

{{Nugget Badge
|title = Cycle 25 Strikes Again
|number = 337
|first_author = Kamil BICZ
|second_author =
|publish_date = 20 November 2018
|description = A second, larger Cycle 25 sunspot
|image=Icon337.png}}

{{Nugget Badge
|title = Remembering Marcos Machado via his research
|number = 336
|first_author = Hugh HUDSON
|second_author =
|publish_date = 13 November 2018
|description = Recalling a friend and colleague, and admiring his final paper
|image=Icon336.png}}

{{Nugget Badge
|title = CORONAS/SPIRIT Mg XII and Nanoflares‎
|number = 335
|first_author = Anton REVA
|second_author =
|publish_date = 22 October 2018
|description = Monochromatic Mg XII spectroheliography sets severe limits on nanoflare heating models
|image=Icon335.png}}

{{Nugget Badge
|title = White-light Emission and Non-thermal Electrons‎
|number = 334
|first_author = Kyoung-Sun LEE
|second_author =
|publish_date = 8 October 2018
|description = An intimate relationship between accelerated electrons and visible flare continuum
|image=Icon334.png}}

{{Nugget Badge
|title = Coronal Hard X-ray Sources Revisited
|number = 333
|first_author = Brian DENNIS
|second_author =
|publish_date = 24 September 2018
|description = Reporting some over-interpretation of the evidence for "coronal thick targets"
|image=Icon333.png}}

{{Nugget Badge
|title = Photospheric response to a flare
|number = 332
|first_author = Mike WHEATLAND
|second_author =
|publish_date = 17 September 2018
|description = Sudden changes in the magnetic field in the low atmosphere associated with particle acceleration
|image=Icon332.png}}

{{Nugget Badge
|title = New Views of Global Solar Magnetic Field Evolution Over Four Solar Cycles
|number = 331
|first_author = David WEBB
|second_author =
|publish_date = 27 August 2018
|description = A digital archive of Pat McIntosh's 44 years of solar synoptic observations
|image=Icon331.png}}

{{Nugget Badge
|title = Understanding the co-spatial return current in solar flares
|number = 330
|first_author = Meriem ALAOUI
|second_author = and Gordon HOLMAN
|publish_date = 6 August 2018
|description = Completing the circuit in a thick-target model
|image=Icon330.png}}

{{Nugget Badge
|title = 3D Magnetic Reconnection at a Coronal Null Point
|number = 329
|first_author = Shane MALONEY,
|second_author = Aidan O'Flannagain and Peter Gallagher
|publish_date = 30 July 2018
|description = Large-scale reconnection involved in Type I radio noise storm
|image=Icon329.png}}

{{Nugget Badge
|title = The true dawn of multimessenger astronomy
|number = 328
|first_author = Hugh Hudson
|second_author =
|publish_date = 23 July 2018
|description = Ever since the Carrington flare
|image=Icon328.png}}

{{Nugget Badge
|title = Microwave Imaging Spectroscopy of Flares is Here‎
|number = 327
|first_author = Dale E. Gary,
|second_author = EOVSA and RHESSI Teams
|publish_date = 16 July 2018
|description = Microwave imaging spectroscopy takes a giant leap forward with SOL2017-09-10
|image=Icon327.png}}

{{Nugget Badge
|title = Coronal nanoflares powered by footpoint reconnection
|number = 326
|first_author = Pradeep Chitta,
|second_author = Hardi Peter, and Sami Solanki
|publish_date = 9 July 2018
|description = Coronal nanoflares in active region cores can be powered by the magnetic reconnection in the lower solar atmosphere
|image=Icon326.png}}

{{Nugget Badge
|title = A remarkable, but confused, coronal hard X-ray source
|number = 325
|first_author = Alexandra Lysenko,
|second_author = Larisa Kashapova and Hugh Hudson
|publish_date = 25 June 2018
|description = A remarkable flare in 1999 adds to our short list of extended coronal hard X-ray/microwave sources
|image=Icon325.png}}

{{Nugget Badge
|title = Understanding HMI pseudocontinuum in white-light flares‎
|number = 324
|first_author = Michal &Scaron;vanda
|second_author = et al.
|publish_date = 28 May 2018
|description = The HMI pseudocontinuum (Ic) is ill-calibrated in regions with strong fields, i.e. for white-light flares
|image=Icon324.png}}

{{Nugget Badge
|title = To beam or not to beam - that is (still) the question
|number = 323
|first_author = Paulo Simões
|second_author = and Hugh Hudson
|publish_date = 14 May 2018
|description = Descriptions of the lower solar atmosphere of flares ca. Cycle 21 sound surprisingly current
|image=Icon323.png}}

{{Nugget Badge
|title = Observation of Cosmic Ray Spallation Events from SoHO‎
|number = 322
|first_author = Serge Koutchmy
|second_author = and Ehsan Tavabi
|publish_date = 7 May 2018
|description = LASCO's images capture high-energy nuclear interactions from cosmic-ray hits
|image=Icon322.png}}

{{Nugget Badge
|title = A Sunspot from Cycle 25 for sure
|number = 321
|first_author = Tomek Mrozek
|second_author = and Hugh Hudson
|publish_date = 10 April 2018
|description = YES! Cycle 25 is here!
|image=Icon321.png}}

{{Nugget Badge
|title = Blue-wing enhancement of the Mg II h and k lines in a flare
|number = 320
|first_author = Akiko TEI
|second_author =
|publish_date = 9 April 2018
|description = Flare loops involve a cool upflow preceding the hot evaporation flow
|image=Icon320.png}}

{{Nugget Badge
|title = NuSTAR detects X-ray flares in the quiet Sun
|number = 319
|first_author = Matej Kuhar
|second_author = and Säm Krucker
|publish_date = 26 March 2018
|description = Quiet-Sun flares may not be powerful, but they look a lot like ordinary flares
|image=Icon319.png}}

{{Nugget Badge
|title = Homologous CME/flares from AR 12371
|number = 318
|first_author = Panditi Vemareddy
|second_author = and Pascal Demoulín
|publish_date = 19 March 2018
|description = An excellent set of homologous flare/CMEs analyzed and explained
|image=Icon318.png}}

{{Nugget Badge
|title = Non-Maxwellian Diagnostics from SDO/EVE Spectra of an X-class Flare
|number = 317
|first_author = Elena Dzifčáková
|second_author = and Jaroslav Dudík
|publish_date = 16 February 2018
|description = Ratios of high-excitation ions can readily detect κ-distributions in flare plasmas
|image=Icon317.png}}

{{Nugget Badge
|title = Joint MinXSS and RHESSI Flare X-ray Spectra between 1 and 15 keV
|number = 316
|first_author = Chris Moore, Brian Dennis and the MinXSS Science Team
|publish_date = 5 February 2018
|description = MinXSS adds systematic views of flare soft X-ray spectra to RHESSI imagery
|image=Icon316.png}}

{{Nugget Badge
|title = Parameterized Flare Models with Chromospheric Compressions
|number = 315
|first_author = Adam Kowalski & Joel Allred
|publish_date = 17 January 2018
|description = A new approach to modeling the lower flare atmosphere
|image=FlareModelsKowalskiAllred.png}}

{{Nugget Badge
|title = A Curious Sunspot Group in 2018
|number = 314
|first_author = Hugh Hudson
|publish_date = 14 January 2018
|description = The first new sunspot group of 2018 emerged at the wrong latitude
|image = Icon314.png}}

{{Nugget Badge
|title = Tecumseh's Eclipse and Astrophysics
|number = 313
|first_author = Hugh Hudson
|publish_date = 25 December 2017
|description = The solar corona was first recognized as such, and named, in an eclipse of 1806
|image = Icon313.png}}

{{Nugget Badge
|title = Hunting for Hidden Tiny Flares
|number = 312
|first_author = Shin-nosuke ISHIKAWA
|publish_date = 27 November 2017
|description = FOXSI-2 says that episodic energy releases are still viable as a part of the coronal heating problem.
|image = Icon312.png}}

{{Nugget Badge
|title = Unusual Type III Burst Dynamics Produced by Diverging Magnetic Fields
|number = 311
|first_author = Patrick McCauley
|publish_date = 20 November 2017
|description = Unusual type III bursts follow coronal separatrix structures.
|image = Icon311.png}}

{{Nugget Badge
|title = Valderrama in the 21st Century
|number = 310
|first_author = Hugh Hudson
|publish_date = 31 October 2017
|description = A newly-described white-light flare from the 19th century!..
|image = Icon310.png}}

{{Nugget Badge
|title = Electron Scattering in the Flaring Corona
|number = 309
|first_author = Sophie Musset
|publish_date = 24 October 2017
|description = Diffusive transport may contribute to the trapping of electrons in coronal X-ray sources
|image = Icon309.png}}

{{Nugget Badge
|title = The Power of Turbulence
|number = 308
|first_author = Nic Bian
|publish_date = 25 September 2017
|description = Turbulent energy content may underlie flare energy transfer, magnetic reconnection, and particle acceleration
|image = Icon308.png}}

{{Nugget Badge
|title = The Kelvin Force and Loop-Top Concentration
|number = 307
|first_author = Kiyoto SHIBASAKI
|publish_date = 18 September 2017
|description = New physics can explain the perplexing overpressure at the flare looptop regions
|image = Icon307.png}}

{{Nugget Badge
|title = The Last Best Flare of Cycle 24?
|number = 306
|first_author = Säm Krucker
|second_author = and Hugh Hudson
|publish_date = 11 September 2017
|description = Right on schedule, Cycle 24 has produced a great flare (with a GLE)
|image = Icon306.png}}

{{Nugget Badge
|title = Electric Current Neutralization and Solar Eruption in Active Regions
|number = 305
|first_author = Yang LIU
|second_author =
|publish_date = 28 August 2017
|description = Active current systems in the solar corona don't have return currents
|image = Icon305.png}}

{{Nugget Badge
|title = RHESSI and the Megamovie
|number = 304
|first_author = Hugh Hudson, Laura Peticolas,
|second_author = and Juan Carlos Martínez Oliveros
|publish_date = 31 July 2017
|description = A wholly new way to view a solar eclipse, and to do solar astrometry
|image = Icon304.png}}

{{Nugget Badge
|title = Bastille Day 2017
|number = 303
|first_author = Hugh Hudson
|second_author = and Säm Krucker
|publish_date = 24 July 2017
|description = Interesting flares really do happen on Bastille Day...
|image = Icon303.png}}

{{Nugget Badge
|title = The Solar X-ray Limb III
|number = 302
|first_author = Marina Battaglia
|second_author = and Gordon Hurford
|publish_date = 12 June 2017
|description = RHESSI succeeds with a wholly new way to measure the solar diameter
|image = Icon302.png}}

{{Nugget Badge
|title = Double Coronal X-ray and Microwave Sources Associated With A Magnetic Breakout Solar Eruption
|number = 301
|first_author = Yao CHEN
|second_author =
|publish_date = 29 May 2017
|description = A different explanation of the double coronal hard X-ray sources
|image = Icon301.png}}

{{Nugget Badge
|title = A Lasso Model for Solar Gamma-ray Events
|number = 300
|first_author = Hugh Hudson
|second_author =
|publish_date = 15 May 2017
|description = A toy model hoping to explain the SEP/LAT relationship
|image = Icon300.png}}

[[RHESSI Science Nuggets 200 to 299|Next Nuggets]]

File:Icon526.png

2026-05-14T10:46:04Z

Hhudson:

X-ray Log Letters

2026-05-14T10:42:04Z

Hhudson: /* Conclusions */

{{Infobox Nugget |name = Nugget
|title = X-ray Log Letters
|number = 526
|first_author = Hugh HUDSON and
|second_author = Ed CLIVER
|publish_date = May 18, 2026
|next_nugget = TBD
|previous_nugget = {{#ask: [[Category:Nugget]] [[RHESSI Nugget Index::525]]}}
}}

== Introduction ==

As all students of solar activity know, the
[https://www.stce.be/educational/classification naming scheme]
for solar flares involves the letters ABCMX.
These date from the dawn of the space age, when the first
[https://en.wikipedia.org/wiki/SOLRAD SOLRAD] satellites began to monitor
solar X-ray emission.
Flares of a wide range of brightnesses were immediately apparent, and
[https://www.noaa.gov NOAA]
ionospheric physicist Don Baker (Ref. [1]) came up with a classification
that matched decades of peak flux to letters: Cnn would mean nn x 10-4,
and the basic flux level 1.0 x 10-6 W/m2 would be class C1.0.
Initially it was just CMX ("Common", "Medium", "Extreme")
Each flare has a peak flux in the standard 1-8 Å band,
and the range of magnitudes of flare peak fluxes is so great that it's most
convenient to record the
[https://en.wikipedia.org/wiki/Common_logarithm logarithm] of the
flux.
This convention moved directly into the
[https://www.swpc.noaa.gov/products/goes-x-ray-flux GOES]
satellite era, and from 1974 the standardized flux measurements
have come from this series of spacecraft (Ref. [2]).

In standard units a C-class flare has a peak flux greater than 10-7
W/m2, with M-class and X-class greater by powers of 10.
Conventionally a flare 10% brighter than the threshold, with peak flux
1.1 x 10-7 W/m2, would then become a C1.1 flare.
The letter thus represents the truncated logarithm of the peak flux.
The magnitudes are not rounded off and represent the solar X-ray flux
conventionally in a 1-min integration interval.
A background quiescent solar emission level is not subtracted; these routine
observations show the total solar X-ray flux in "Sun-as-a-star" mode.
Weaker events near the background level, which can indeed exceed C1 during
active times, will thus not be quite as energetic as their name implies.

Low background solar X-ray fluxes during solar minima allowed the GOES
detector technology to detect fainter events, and so two new decades were
added to the letter string: A and B, with no particular descriptive
interpretation.
Thus we arrived at the current letter string ABCMX.

== The SphinX breakthrough (to the bottom) ==

The first routine flare monitoring with sufficient sensitivity to
detect the solar quiescent X-ray flux appeared with the SphinX
instrument from the
[https://scholar.google.com/citations?user=vDLMZPIAAAAJ&hl=pl Sylwester]
group at Wroc&lstrok;aw (Ref. [3]).
For 1-8 Å this turned out to be about two decades below the A level.
Hence, two more letters: Q "quiet" and S "small", leading to the more complete
string QSABCMX.
Figure 1 shows SphinX data from the 2009
[https://en.wikipedia.org/wiki/Solar_cycle solar minimum].

[[File:526f1.png|center|thumb|600px|caption|Figure 1: 
SphinX observations from solar minimum 2009.
The regions marked with blue show the detection of the corona, at levels far
below the original CMX range (Ref. [3]).
Excesses above this level are due to weak flares and quiescent active regions.
Translated to the GOES calibration, the weakest events are measured in units of
10-10 W/m2.
]]

== The greatest events (to the top) ==

At the top end of the GOES soft X-ray distribution, a handful of the most
extreme events had saturated the GOES 1-8 Å readout.
Ref. [4] describes an evenhanded patching of these items, together with a
correction for a systematic offset (Ref. [2]).
This produced a list of 37 >X10 events after background subtraction.
This basic manipulation departs from tradition, and so we provide this
[greatest flares]
catalog using the letter system "QSabcmxyz".
To translate, the new "y" class is the old "X10" class, sometimes now called
"S" (Ref. 5]), and the new catalog lists 37 of them.
The new "z" class has no examples yet (but we're hopeful), although the
[https://heliowiki.smce.nasa.gov/wiki/index.php/The_1859_Space_Weather_Event_Revisited Carrington event]
might have been in that category.

A sample of the newly lettered catalog is here, representing a signal-to-background requirement of 1 (flare
doubles the preflare level), resulting in a reduction of total number from 48,131 to 42,469 for the timespan
1974-2023.
The new letter string is QSabcmxyz, pleasingly symmetric.
SOL1984-02-10T22:47 C9.1 m1.21
SOL1984-02-11T01:31 C3.7 c3.78
SOL1984-02-11T02:45 M2.9 m4.07
SOL1984-02-11T03:44 C2.0 c1.93
SOL1984-02-11T04:33 C2.1 c1.78
SOL1984-02-11T04:56 C2.1 c2.23
SOL1984-02-11T09:06 C2.6 c2.46
SOL1984-02-11T10:09 C1.8 c1.43
SOL1984-02-11T12:16 C3.0 c3.19
SOL1984-02-11T14:24 C4.8 c6.03
The catalog contains 37 y-class events (previously X10 or S), but no z-class examples because the Sun refuses to
cooperate. At the C->c level, many events get downgraded because of background subtraction, but the systematic
historical scale adjustment described in Ref. [2] tends to compensate for that.

== Conclusions ==

See the [https://www.astro.gla.ac.uk/users/hsh3f/QSabcmxyz.html further discussion] of how QSabcmxyz works, or to access it directly click [https://www.astro.gla.ac.uk/users/hsh3f/QSabcmxyz.txt here] for a 2-MB text listing.

== References ==

[1] "Sentinels of the sun: forecasting space weather," B. Poppe and K. Jorden, 2006

[2] [https://www.sciencedirect.com/science/article/pii/B9780128143278000196 "GOES-R Series Solar X-ray and Ultraviolet Irradiance"]

[3] [http://adsabs.harvard.edu/abs/2011SoSyR..45..182G "Soft X-ray variability over the present minimum of solar activity as observed by SphinX"]

[4] [https://ui.adsabs.harvard.edu/abs/2024SoPh..299...39H "The Greatest GOES Soft X-ray Flares"]

[5] [https://ui.adsabs.harvard.edu/abs/2025ApJ...979L..16T "The Occurrence of Powerful Flares Stronger than X10 Class in Solar Cycles"]

X-ray Log Letters

2026-05-13T18:51:21Z

Hhudson: No, 526 initial

{{Infobox Nugget |name = Nugget
|title = X-ray Log Letters
|number = 526
|first_author = Hugh HUDSON and
|second_author = Ed CLIVER
|publish_date = May 18, 2026
|next_nugget = TBD
|previous_nugget = {{#ask: [[Category:Nugget]] [[RHESSI Nugget Index::525]]}}
}}

== Introduction ==

As all students of solar activity know, the
[https://www.stce.be/educational/classification naming scheme]
for solar flares involves the letters ABCMX.
These date from the dawn of the space age, when the first
[https://en.wikipedia.org/wiki/SOLRAD SOLRAD] satellites began to monitor
solar X-ray emission.
Flares of a wide range of brightnesses were immediately apparent, and
[https://www.noaa.gov NOAA]
ionospheric physicist Don Baker (Ref. [1]) came up with a classification
that matched decades of peak flux to letters: Cnn would mean nn x 10-4,
and the basic flux level 1.0 x 10-6 W/m2 would be class C1.0.
Initially it was just CMX ("Common", "Medium", "Extreme")
Each flare has a peak flux in the standard 1-8 Å band,
and the range of magnitudes of flare peak fluxes is so great that it's most
convenient to record the
[https://en.wikipedia.org/wiki/Common_logarithm logarithm] of the
flux.
This convention moved directly into the
[https://www.swpc.noaa.gov/products/goes-x-ray-flux GOES]
satellite era, and from 1974 the standardized flux measurements
have come from this series of spacecraft (Ref. [2]).

In standard units a C-class flare has a peak flux greater than 10-7
W/m2, with M-class and X-class greater by powers of 10.
Conventionally a flare 10% brighter than the threshold, with peak flux
1.1 x 10-7 W/m2, would then become a C1.1 flare.
The letter thus represents the truncated logarithm of the peak flux.
The magnitudes are not rounded off and represent the solar X-ray flux
conventionally in a 1-min integration interval.
A background quiescent solar emission level is not subtracted; these routine
observations show the total solar X-ray flux in "Sun-as-a-star" mode.
Weaker events near the background level, which can indeed exceed C1 during
active times, will thus not be quite as energetic as their name implies.

Low background solar X-ray fluxes during solar minima allowed the GOES
detector technology to detect fainter events, and so two new decades were
added to the letter string: A and B, with no particular descriptive
interpretation.
Thus we arrived at the current letter string ABCMX.

== The SphinX breakthrough (to the bottom) ==

The first routine flare monitoring with sufficient sensitivity to
detect the solar quiescent X-ray flux appeared with the SphinX
instrument from the
[https://scholar.google.com/citations?user=vDLMZPIAAAAJ&hl=pl Sylwester]
group at Wroc&lstrok;aw (Ref. [3]).
For 1-8 Å this turned out to be about two decades below the A level.
Hence, two more letters: Q "quiet" and S "small", leading to the more complete
string QSABCMX.
Figure 1 shows SphinX data from the 2009
[https://en.wikipedia.org/wiki/Solar_cycle solar minimum].

[[File:526f1.png|center|thumb|600px|caption|Figure 1: 
SphinX observations from solar minimum 2009.
The regions marked with blue show the detection of the corona, at levels far
below the original CMX range (Ref. [3]).
Excesses above this level are due to weak flares and quiescent active regions.
Translated to the GOES calibration, the weakest events are measured in units of
10-10 W/m2.
]]

== The greatest events (to the top) ==

At the top end of the GOES soft X-ray distribution, a handful of the most
extreme events had saturated the GOES 1-8 Å readout.
Ref. [4] describes an evenhanded patching of these items, together with a
correction for a systematic offset (Ref. [2]).
This produced a list of 37 >X10 events after background subtraction.
This basic manipulation departs from tradition, and so we provide this
[greatest flares]
catalog using the letter system "QSabcmxyz".
To translate, the new "y" class is the old "X10" class, sometimes now called
"S" (Ref. 5]), and the new catalog lists 37 of them.
The new "z" class has no examples yet (but we're hopeful), although the
[https://heliowiki.smce.nasa.gov/wiki/index.php/The_1859_Space_Weather_Event_Revisited Carrington event]
might have been in that category.

A sample of the newly lettered catalog is here, representing a signal-to-background requirement of 1 (flare
doubles the preflare level), resulting in a reduction of total number from 48,131 to 42,469 for the timespan
1974-2023.
The new letter string is QSabcmxyz, pleasingly symmetric.
SOL1984-02-10T22:47 C9.1 m1.21
SOL1984-02-11T01:31 C3.7 c3.78
SOL1984-02-11T02:45 M2.9 m4.07
SOL1984-02-11T03:44 C2.0 c1.93
SOL1984-02-11T04:33 C2.1 c1.78
SOL1984-02-11T04:56 C2.1 c2.23
SOL1984-02-11T09:06 C2.6 c2.46
SOL1984-02-11T10:09 C1.8 c1.43
SOL1984-02-11T12:16 C3.0 c3.19
SOL1984-02-11T14:24 C4.8 c6.03
The catalog contains 37 y-class events (previously X10 or S), but no z-class examples because the Sun refuses to
cooperate. At the C->c level, many events get downgraded because of background subtraction, but the systematic
historical scale adjustment described in Ref. [2] tends to compensate for that.

== Conclusions ==

Enjoy your beautiful GOES data!

== References ==

[1] "Sentinels of the sun: forecasting space weather," B. Poppe and K. Jorden, 2006

[2] [https://www.sciencedirect.com/science/article/pii/B9780128143278000196 "GOES-R Series Solar X-ray and Ultraviolet Irradiance"]

[3] [http://adsabs.harvard.edu/abs/2011SoSyR..45..182G "Soft X-ray variability over the present minimum of solar activity as observed by SphinX"]

[4] [https://ui.adsabs.harvard.edu/abs/2024SoPh..299...39H "The Greatest GOES Soft X-ray Flares"]

[5] [https://ui.adsabs.harvard.edu/abs/2025ApJ...979L..16T "The Occurrence of Powerful Flares Stronger than X10 Class in Solar Cycles"]

X-ray Log Letters

2026-05-13T18:31:03Z

Hhudson: /* The greatest events (to the top) */

{{Infobox Nugget |name = Nugget
|title = X-ray Log Letters
|number = 526
|first_author = Hugh HUDSON and
|second_author = Ed CLIVER
|publish_date = May 18, 2026
|next_nugget = TBD
|previous_nugget = {{#ask: [[Category:Nugget]] [[RHESSI Nugget Index::525]]}}
}}

== Introduction ==

As all students of solar activity know, the
[https://www.stce.be/educational/classification naming scheme]
for solar flares involves the letters ABCMX.
These date from the dawn of the space age, when the first
[https://en.wikipedia.org/wiki/SOLRAD SOLRAD] satellites began to monitor
solar X-ray emission.
Flares of a wide range of brightnesses were immediately apparent, and
[https://www.noaa.gov NOAA]
ionospheric physicist Don Baker (Ref. [1]) came up with a classification
that matched decades of peak flux to letters: Cnn would mean nn x 10-4,
and the basic flux level 1.0 x 10-6 W/m2 would be class C1.0.
Initially it was just CMX ("Common", "Medium", "Extreme")
Each flare has a peak flux in the standard 1-8 Å band,
and the range of magnitudes of flare peak fluxes is so great that it's most
convenient to record the
[https://en.wikipedia.org/wiki/Common_logarithm logarithm] of the
flux.
This convention moved directly into the
[https://www.swpc.noaa.gov/products/goes-x-ray-flux GOES]
satellite era, and from 1974 the standardized flux measurements
have come from this series of spacecraft (Ref. [2]).

In standard units a C-class flare has a peak flux greater than 10-7
W/m2, with M-class and X-class greater by powers of 10.
Conventionally a flare 10% brighter than the threshold, with peak flux
1.1 x 10-7 W/m2, would then become a C1.1 flare.
The letter thus represents the truncated logarithm of the peak flux.
The magnitudes are not rounded off and represent the solar X-ray flux
conventionally in a 1-min integration interval.
A background quiescent solar emission level is not subtracted; these routine
observations show the total solar X-ray flux in "Sun-as-a-star" mode.
Weaker events near the background level, which can indeed exceed C1 during
active times, will thus not be quite as energetic as their name implies.

Low background solar X-ray fluxes during solar minima allowed the GOES
detector technology to detect fainter events, and so two new decades were
added to the letter string: A and B, with no particular descriptive
interpretation.
Thus we arrived at the current letter string ABCMX.

== The SphinX breakthrough (to the bottom) ==

The first routine flare monitoring with sufficient sensitivity to
detect the solar quiescent X-ray flux appeared with the SphinX
instrument from the
[https://scholar.google.com/citations?user=vDLMZPIAAAAJ&hl=pl Sylwester]
group at Wroc&lstrok;aw (Ref. [3]).
For 1-8 Å this turned out to be about two decades below the A level.
Hence, two more letters: Q "quiet" and S "small", leading to the more complete
string QSABCMX.
Figure 1 shows SphinX data from the 2009
[https://en.wikipedia.org/wiki/Solar_cycle solar minimum].

[[File:526f1.png|center|thumb|600px|caption|Figure 1: 
SphinX observations from solar minimum 2009.
The regions marked with blue show the detection of the corona, at levels far
below the original CMX range (Ref. [3]).
Excesses above this level are due to weak flares and quiescent active regions.
Translated to the GOES calibration, the weakest events are measured in units of
10-10 W/m2.
]]

== The greatest events (to the top) ==

At the top end of the GOES soft X-ray distribution, a handful of the most
extreme events had saturated the GOES 1-8 Å readout.
Ref. [4] describes an evenhanded patching of these items, together with a
correction for a systematic offset (Ref. [2]).
This produced a list of 37 >X10 events after background subtraction.
This basic manipulation departs from tradition, and so we provide this
[greatest flares]
catalog using the letter system "QSabcmxyz".
To translate, the new "y" class is the old "X10" class, sometimes now called
"S" (Ref. 5]), and the new catalog lists 37 of them.
The new "z" class has no examples yet (but we're hopeful), although the
[https://heliowiki.smce.nasa.gov/wiki/index.php/The_1859_Space_Weather_Event_Revisited Carrington event]
might have been in that category.

== Conclusions ==

== References ==

[1] "Sentinels of the sun: forecasting space weather," B. Poppe and K. Jorden, 2006

[2] [https://www.sciencedirect.com/science/article/pii/B9780128143278000196 "GOES-R Series Solar X-ray and Ultraviolet Irradiance"]

[3] [http://adsabs.harvard.edu/abs/2011SoSyR..45..182G "Soft X-ray variability over the present minimum of solar activity as observed by SphinX"]

[4] [https://ui.adsabs.harvard.edu/abs/2024SoPh..299...39H "The Greatest GOES Soft X-ray Flares"]

[5] [https://ui.adsabs.harvard.edu/abs/2025ApJ...979L..16T "The Occurrence of Powerful Flares Stronger than X10 Class in Solar Cycles"]

X-ray Log Letters

2026-05-13T18:29:17Z

Hhudson: /* The SphinX breakthrough (to the bottom) */

{{Infobox Nugget |name = Nugget
|title = X-ray Log Letters
|number = 526
|first_author = Hugh HUDSON and
|second_author = Ed CLIVER
|publish_date = May 18, 2026
|next_nugget = TBD
|previous_nugget = {{#ask: [[Category:Nugget]] [[RHESSI Nugget Index::525]]}}
}}

== Introduction ==

As all students of solar activity know, the
[https://www.stce.be/educational/classification naming scheme]
for solar flares involves the letters ABCMX.
These date from the dawn of the space age, when the first
[https://en.wikipedia.org/wiki/SOLRAD SOLRAD] satellites began to monitor
solar X-ray emission.
Flares of a wide range of brightnesses were immediately apparent, and
[https://www.noaa.gov NOAA]
ionospheric physicist Don Baker (Ref. [1]) came up with a classification
that matched decades of peak flux to letters: Cnn would mean nn x 10-4,
and the basic flux level 1.0 x 10-6 W/m2 would be class C1.0.
Initially it was just CMX ("Common", "Medium", "Extreme")
Each flare has a peak flux in the standard 1-8 Å band,
and the range of magnitudes of flare peak fluxes is so great that it's most
convenient to record the
[https://en.wikipedia.org/wiki/Common_logarithm logarithm] of the
flux.
This convention moved directly into the
[https://www.swpc.noaa.gov/products/goes-x-ray-flux GOES]
satellite era, and from 1974 the standardized flux measurements
have come from this series of spacecraft (Ref. [2]).

In standard units a C-class flare has a peak flux greater than 10-7
W/m2, with M-class and X-class greater by powers of 10.
Conventionally a flare 10% brighter than the threshold, with peak flux
1.1 x 10-7 W/m2, would then become a C1.1 flare.
The letter thus represents the truncated logarithm of the peak flux.
The magnitudes are not rounded off and represent the solar X-ray flux
conventionally in a 1-min integration interval.
A background quiescent solar emission level is not subtracted; these routine
observations show the total solar X-ray flux in "Sun-as-a-star" mode.
Weaker events near the background level, which can indeed exceed C1 during
active times, will thus not be quite as energetic as their name implies.

Low background solar X-ray fluxes during solar minima allowed the GOES
detector technology to detect fainter events, and so two new decades were
added to the letter string: A and B, with no particular descriptive
interpretation.
Thus we arrived at the current letter string ABCMX.

== The SphinX breakthrough (to the bottom) ==

The first routine flare monitoring with sufficient sensitivity to
detect the solar quiescent X-ray flux appeared with the SphinX
instrument from the
[https://scholar.google.com/citations?user=vDLMZPIAAAAJ&hl=pl Sylwester]
group at Wroc&lstrok;aw (Ref. [3]).
For 1-8 Å this turned out to be about two decades below the A level.
Hence, two more letters: Q "quiet" and S "small", leading to the more complete
string QSABCMX.
Figure 1 shows SphinX data from the 2009
[https://en.wikipedia.org/wiki/Solar_cycle solar minimum].

[[File:526f1.png|center|thumb|600px|caption|Figure 1: 
SphinX observations from solar minimum 2009.
The regions marked with blue show the detection of the corona, at levels far
below the original CMX range (Ref. [3]).
Excesses above this level are due to weak flares and quiescent active regions.
Translated to the GOES calibration, the weakest events are measured in units of
10-10 W/m2.
]]

== The greatest events (to the top) ==

At the top end of the GOES soft X-ray distribution, a handful of the most
extreme events had saturated the 1-8 Å readout.
Ref. [4] describes an evenhanded patching of these items, together with a
correcting for a systematic offset (Ref. [2]).
This produced a list of 37 >X10 events after background subtraction.
This basic manipulation departs from tradition, and so we provide this
[greatest flares]
catalog using the letter system "QSabcmxyz".
To translate, the new "y" class is the old "X10" class, sometimes now called
"S" (Ref. 5]), and the new catalog lists 37 of them.
The new "z" class has no examples yet (but we're hopeful), although the
[https://heliowiki.smce.nasa.gov/wiki/index.php/The_1859_Space_Weather_Event_Revisited Carrington event]
might have been in that category.

== Conclusions ==

== References ==

[1] "Sentinels of the sun: forecasting space weather," B. Poppe and K. Jorden, 2006

[2] [https://www.sciencedirect.com/science/article/pii/B9780128143278000196 "GOES-R Series Solar X-ray and Ultraviolet Irradiance"]

[3] [http://adsabs.harvard.edu/abs/2011SoSyR..45..182G "Soft X-ray variability over the present minimum of solar activity as observed by SphinX"]

[4] [https://ui.adsabs.harvard.edu/abs/2024SoPh..299...39H "The Greatest GOES Soft X-ray Flares"]

[5] [https://ui.adsabs.harvard.edu/abs/2025ApJ...979L..16T "The Occurrence of Powerful Flares Stronger than X10 Class in Solar Cycles"]

X-ray Log Letters

2026-05-13T18:26:50Z

Hhudson: /* Introduction */

{{Infobox Nugget |name = Nugget
|title = X-ray Log Letters
|number = 526
|first_author = Hugh HUDSON and
|second_author = Ed CLIVER
|publish_date = May 18, 2026
|next_nugget = TBD
|previous_nugget = {{#ask: [[Category:Nugget]] [[RHESSI Nugget Index::525]]}}
}}

== Introduction ==

As all students of solar activity know, the
[https://www.stce.be/educational/classification naming scheme]
for solar flares involves the letters ABCMX.
These date from the dawn of the space age, when the first
[https://en.wikipedia.org/wiki/SOLRAD SOLRAD] satellites began to monitor
solar X-ray emission.
Flares of a wide range of brightnesses were immediately apparent, and
[https://www.noaa.gov NOAA]
ionospheric physicist Don Baker (Ref. [1]) came up with a classification
that matched decades of peak flux to letters: Cnn would mean nn x 10-4,
and the basic flux level 1.0 x 10-6 W/m2 would be class C1.0.
Initially it was just CMX ("Common", "Medium", "Extreme")
Each flare has a peak flux in the standard 1-8 Å band,
and the range of magnitudes of flare peak fluxes is so great that it's most
convenient to record the
[https://en.wikipedia.org/wiki/Common_logarithm logarithm] of the
flux.
This convention moved directly into the
[https://www.swpc.noaa.gov/products/goes-x-ray-flux GOES]
satellite era, and from 1974 the standardized flux measurements
have come from this series of spacecraft (Ref. [2]).

In standard units a C-class flare has a peak flux greater than 10-7
W/m2, with M-class and X-class greater by powers of 10.
Conventionally a flare 10% brighter than the threshold, with peak flux
1.1 x 10-7 W/m2, would then become a C1.1 flare.
The letter thus represents the truncated logarithm of the peak flux.
The magnitudes are not rounded off and represent the solar X-ray flux
conventionally in a 1-min integration interval.
A background quiescent solar emission level is not subtracted; these routine
observations show the total solar X-ray flux in "Sun-as-a-star" mode.
Weaker events near the background level, which can indeed exceed C1 during
active times, will thus not be quite as energetic as their name implies.

Low background solar X-ray fluxes during solar minima allowed the GOES
detector technology to detect fainter events, and so two new decades were
added to the letter string: A and B, with no particular descriptive
interpretation.
Thus we arrived at the current letter string ABCMX.

== The SphinX breakthrough (to the bottom) ==

The first routine flare monitoring with sufficient sensitivity to
detect the solar quiescent X-ray flux appeared with the SphinX
instrument from the
[https://scholar.google.com/citations?user=vDLMZPIAAAAJ&hl=pl Sylwester]
group at Wroc&lstrok;aw (Ref. [3]).
For 1-8 Å this turned out to be about two decades below the A level.
Hence, two more letters: Q "quiet" and S "small", leading to the more complete
string QSABCMX.
Figure 1 shows SphinX data from the 2009
[https://en.wikipedia.org/wiki/Solar_cycle solar minimum].

[[File:526f1.png|center|thumb|600px|caption|Figure 1: 
SphinX observations from solar minimum 2009.
The regions marked with blue show the detection of the corona, at levels far
below the original CMX range (Ref. [3]).
Excesses above this level are due to weak flares and quiescent active regions.
]]

== The greatest events (to the top) ==

At the top end of the GOES soft X-ray distribution, a handful of the most
extreme events had saturated the 1-8 Å readout.
Ref. [4] describes an evenhanded patching of these items, together with a
correcting for a systematic offset (Ref. [2]).
This produced a list of 37 >X10 events after background subtraction.
This basic manipulation departs from tradition, and so we provide this
[greatest flares]
catalog using the letter system "QSabcmxyz".
To translate, the new "y" class is the old "X10" class, sometimes now called
"S" (Ref. 5]), and the new catalog lists 37 of them.
The new "z" class has no examples yet (but we're hopeful), although the
[https://heliowiki.smce.nasa.gov/wiki/index.php/The_1859_Space_Weather_Event_Revisited Carrington event]
might have been in that category.

== Conclusions ==

== References ==

[1] "Sentinels of the sun: forecasting space weather," B. Poppe and K. Jorden, 2006

[2] [https://www.sciencedirect.com/science/article/pii/B9780128143278000196 "GOES-R Series Solar X-ray and Ultraviolet Irradiance"]

[3] [http://adsabs.harvard.edu/abs/2011SoSyR..45..182G "Soft X-ray variability over the present minimum of solar activity as observed by SphinX"]

[4] [https://ui.adsabs.harvard.edu/abs/2024SoPh..299...39H "The Greatest GOES Soft X-ray Flares"]

[5] [https://ui.adsabs.harvard.edu/abs/2025ApJ...979L..16T "The Occurrence of Powerful Flares Stronger than X10 Class in Solar Cycles"]

X-ray Log Letters

2026-05-13T18:26:12Z

Hhudson: /* Introduction */

{{Infobox Nugget |name = Nugget
|title = X-ray Log Letters
|number = 526
|first_author = Hugh HUDSON and
|second_author = Ed CLIVER
|publish_date = May 18, 2026
|next_nugget = TBD
|previous_nugget = {{#ask: [[Category:Nugget]] [[RHESSI Nugget Index::525]]}}
}}

== Introduction ==

As all students of solar activity know, the
[https://www.stce.be/educational/classification naming scheme]
for solar flares involves the letters ABCMX.
These date from the dawn of the space age, when the first
[https://en.wikipedia.org/wiki/SOLRAD SOLRAD] satellites began to monitor
solar X-ray emission.
Flares of a wide range of brightnesses were immediately apparent, and
[https://www.noaa.gov NOAA]
ionospheric physicist Don Baker (Ref. [1]) came up with a classification
that matched decades of peak flux to letters: Cnn would mean nn x 10-4,
and the basic flux level 1.0 x 10-6 W/m2 would be class C1.0.
Initially it was just CMX ("Common", "Medium", "Extreme")
Each flare has a peak flux in the standard 1-8 Å band,
and the range of magnitudes of flare peak fluxes is so great that it's most
convenient to record the
[https://en.wikipedia.org/wiki/Common_logarithm logarithm] of the
flux.
This convention moved directly into the
[https://www.swpc.noaa.gov/products/goes-x-ray-flux GOES]
satellite era, and from 1974 the standardized flux measurements
have come from this series of spacecraft (Ref. [2]).

In standard units a C-class flare has a peak flux greater than 10-7
W/m2, with M-class and X-class greater by powers of 10.
Conventionally a flare 10% brighter than the threshold, with peak flux
1.1 x 10-7 W/m2, would then become a C1.1 flare.
The letter thus represents the truncated logarithm of the peak flux.
The magnitudes are not rounded off and represent the solar X-ray flux
conventionally in a 1-min integration interval.
A background quiescent solar emission level is not subtracted; these routine
observations show the total solar X-ray flux in "Sun-as-a-star" mode.
Weaker events near the background level, which can indeed exceed C1 during
active times, will thus not be quite as energetic as their name implies.

Low background solar X-ray fluxes during solar minima allowed the GOES
detector technology to detect fainter events, and so two new decades were
added to the letter string: A and B, with no particular descriptive
interpretation.
Thus we have ABCMX.

== The SphinX breakthrough (to the bottom) ==

The first routine flare monitoring with sufficient sensitivity to
detect the solar quiescent X-ray flux appeared with the SphinX
instrument from the
[https://scholar.google.com/citations?user=vDLMZPIAAAAJ&hl=pl Sylwester]
group at Wroc&lstrok;aw (Ref. [3]).
For 1-8 Å this turned out to be about two decades below the A level.
Hence, two more letters: Q "quiet" and S "small", leading to the more complete
string QSABCMX.
Figure 1 shows SphinX data from the 2009
[https://en.wikipedia.org/wiki/Solar_cycle solar minimum].

[[File:526f1.png|center|thumb|600px|caption|Figure 1: 
SphinX observations from solar minimum 2009.
The regions marked with blue show the detection of the corona, at levels far
below the original CMX range (Ref. [3]).
Excesses above this level are due to weak flares and quiescent active regions.
]]

== The greatest events (to the top) ==

At the top end of the GOES soft X-ray distribution, a handful of the most
extreme events had saturated the 1-8 Å readout.
Ref. [4] describes an evenhanded patching of these items, together with a
correcting for a systematic offset (Ref. [2]).
This produced a list of 37 >X10 events after background subtraction.
This basic manipulation departs from tradition, and so we provide this
[greatest flares]
catalog using the letter system "QSabcmxyz".
To translate, the new "y" class is the old "X10" class, sometimes now called
"S" (Ref. 5]), and the new catalog lists 37 of them.
The new "z" class has no examples yet (but we're hopeful), although the
[https://heliowiki.smce.nasa.gov/wiki/index.php/The_1859_Space_Weather_Event_Revisited Carrington event]
might have been in that category.

== Conclusions ==

== References ==

[1] "Sentinels of the sun: forecasting space weather," B. Poppe and K. Jorden, 2006

[2] [https://www.sciencedirect.com/science/article/pii/B9780128143278000196 "GOES-R Series Solar X-ray and Ultraviolet Irradiance"]

[3] [http://adsabs.harvard.edu/abs/2011SoSyR..45..182G "Soft X-ray variability over the present minimum of solar activity as observed by SphinX"]

[4] [https://ui.adsabs.harvard.edu/abs/2024SoPh..299...39H "The Greatest GOES Soft X-ray Flares"]

[5] [https://ui.adsabs.harvard.edu/abs/2025ApJ...979L..16T "The Occurrence of Powerful Flares Stronger than X10 Class in Solar Cycles"]

X-ray Log Letters

2026-05-13T18:24:53Z

Hhudson: /* Introduction */

{{Infobox Nugget |name = Nugget
|title = X-ray Log Letters
|number = 526
|first_author = Hugh HUDSON and
|second_author = Ed CLIVER
|publish_date = May 18, 2026
|next_nugget = TBD
|previous_nugget = {{#ask: [[Category:Nugget]] [[RHESSI Nugget Index::525]]}}
}}

== Introduction ==

As all students of solar activity know, the
[https://www.stce.be/educational/classification naming scheme]
for solar flares involves the letters ABCMX.
These date from the dawn of the space age, when the first
[https://en.wikipedia.org/wiki/SOLRAD SOLRAD] satellites began to monitor
solar X-ray emission.
Flares of a wide range of brightnesses were immediately apparent, and
[https://www.noaa.gov NOAA]
ionospheric physicist Don Baker (Ref. [1]) came up with a classification
that matched decades of peak flux to letters: Cnn would mean nn x 10-4,
and the basic flux level 1.0 x 10-6 W/m2 would be class C1.0.
Initially it was just CMX ("Common", "Medium", "Extreme")
Each flare has a peak flux in the standard 1-8 Å band,
and the range of magnitudes of flare peak fluxes is so great that it's most
convenient to record the
[https://en.wikipedia.org/wiki/Common_logarithm logarithm] of the
flux.
This convention moved directly into the
[https://www.swpc.noaa.gov/products/goes-x-ray-flux GOES]
satellite era, and from 1974 the standardized flux measurements
have come from this series of spacecraft (Ref. [2]).

In standard units a C-class flare has a peak flux greater than 10-7
W/m2, with M-class and X-class greater by powers of 10.
Conventionally a flare 10% brighter than the threshold, with peak flux
1.1 x 10-7 W/m2, would then become a C1.1 flare.
The letter thus represents the truncated logarithm of the peak flux.
The magnitudes are not rounded off and represent the solar X-ray flux
conventionally in a 1-min integration interval.
A background quiescent solar emission level is not subtracted; these routine
observations show the total solar X-ray flux in "Sun-as-a-star" mode.
Weaker events near the background level, which can indeed exceed C1 during
active times, will thus not be quite as energetic as their name implies.

Low background solar X-ray fluxes during solar minima allowed the GOES
detector technology to detect fainter events, and so two new decades were
added to the letter string: A and B, with no descriptive term ("Boring" and
"Anemic" come to mind).
Thus we have ABCMX.

== The SphinX breakthrough (to the bottom) ==

The first routine flare monitoring with sufficient sensitivity to
detect the solar quiescent X-ray flux appeared with the SphinX
instrument from the
[https://scholar.google.com/citations?user=vDLMZPIAAAAJ&hl=pl Sylwester]
group at Wroc&lstrok;aw (Ref. [3]).
For 1-8 Å this turned out to be about two decades below the A level.
Hence, two more letters: Q "quiet" and S "small", leading to the more complete
string QSABCMX.
Figure 1 shows SphinX data from the 2009
[https://en.wikipedia.org/wiki/Solar_cycle solar minimum].

[[File:526f1.png|center|thumb|600px|caption|Figure 1: 
SphinX observations from solar minimum 2009.
The regions marked with blue show the detection of the corona, at levels far
below the original CMX range (Ref. [3]).
Excesses above this level are due to weak flares and quiescent active regions.
]]

== The greatest events (to the top) ==

At the top end of the GOES soft X-ray distribution, a handful of the most
extreme events had saturated the 1-8 Å readout.
Ref. [4] describes an evenhanded patching of these items, together with a
correcting for a systematic offset (Ref. [2]).
This produced a list of 37 >X10 events after background subtraction.
This basic manipulation departs from tradition, and so we provide this
[greatest flares]
catalog using the letter system "QSabcmxyz".
To translate, the new "y" class is the old "X10" class, sometimes now called
"S" (Ref. 5]), and the new catalog lists 37 of them.
The new "z" class has no examples yet (but we're hopeful), although the
[https://heliowiki.smce.nasa.gov/wiki/index.php/The_1859_Space_Weather_Event_Revisited Carrington event]
might have been in that category.

== Conclusions ==

== References ==

[1] "Sentinels of the sun: forecasting space weather," B. Poppe and K. Jorden, 2006

[2] [https://www.sciencedirect.com/science/article/pii/B9780128143278000196 "GOES-R Series Solar X-ray and Ultraviolet Irradiance"]

[3] [http://adsabs.harvard.edu/abs/2011SoSyR..45..182G "Soft X-ray variability over the present minimum of solar activity as observed by SphinX"]

[4] [https://ui.adsabs.harvard.edu/abs/2024SoPh..299...39H "The Greatest GOES Soft X-ray Flares"]

[5] [https://ui.adsabs.harvard.edu/abs/2025ApJ...979L..16T "The Occurrence of Powerful Flares Stronger than X10 Class in Solar Cycles"]

X-ray Log Letters

2026-05-11T18:31:11Z

Hhudson: Most of No. 526

{{Infobox Nugget |name = Nugget
|title = X-ray Log Letters
|number = 526
|first_author = Hugh HUDSON and
|second_author = Ed CLIVER
|publish_date = May 18, 2026
|next_nugget = TBD
|previous_nugget = {{#ask: [[Category:Nugget]] [[RHESSI Nugget Index::525]]}}
}}

== Introduction ==

As all students of solar activity know, the
[https://www.stce.be/educational/classification naming scheme]
for solar flares involves the letters ABCMX.
These date from the dawn of the space age, when the first
[https://en.wikipedia.org/wiki/SOLRAD SOLRAD] satellites began to monitor
solar X-ray emission.
Flares of a wide range of brightnesses were immediately apparent, and
[https://www.noaa.gov NOAA]
ionospheric physicist Don Baker (Ref. [1]) came up with the classification.
Initially it was just CMX ("Common", "Medium", "Extreme")
Each flare has a peak flux in the standard 1-8 Å band,
and the range of magnitudes of flare peak fluxes is so great that it's most
convenient to record the
[https://en.wikipedia.org/wiki/Common_logarithm logarithm] of the
flux.
This convention moved directly into the
[https://www.swpc.noaa.gov/products/goes-x-ray-flux GOES]
satellite era, and from 1974 the standardized flux measurements
have come from this series of spacecraft (Ref. [2]).

In standard units a C-class flare has a peak flux greater than 10-7
W/m2, with M-class and X-class greater by powers of 10.
Conventionally a flare 10% brighter than the threshold, with peak flux
1.1 x 10-7 W/m2, would then become a C1.1 flare.
The letter thus represents the truncated logarithm of the peak flux.
The magnitudes are not rounded off and represent the solar X-ray flux
conventionally in a 1-min integration interval.
A background quiescent solar emission level is not subtracted; these routine
observations show the total solar X-ray flux in "Sun-as-a-star" mode.
Weaker events near the background level, which can indeed exceed C1 during
active times, will thus not be quite as energetic as their name implies.

Low background solar X-ray fluxes during solar minima allowed the GOES
detector technology to detect fainter events, and so two new decades were
added to the letter string: A and B, with no descriptive term ("Boring" and
"Anemic" come to mind).
Thus we have ABCMX.

== The SphinX breakthrough (to the bottom) ==

The first routine flare monitoring with sufficient sensitivity to
detect the solar quiescent X-ray flux appeared with the SphinX
instrument from the
[https://scholar.google.com/citations?user=vDLMZPIAAAAJ&hl=pl Sylwester]
group at Wroc&lstrok;aw (Ref. [3]).
For 1-8 Å this turned out to be about two decades below the A level.
Hence, two more letters: Q "quiet" and S "small", leading to the more complete
string QSABCMX.
Figure 1 shows SphinX data from the 2009
[https://en.wikipedia.org/wiki/Solar_cycle solar minimum].

[[File:526f1.png|center|thumb|600px|caption|Figure 1: 
SphinX observations from solar minimum 2009.
The regions marked with blue show the detection of the corona, at levels far
below the original CMX range (Ref. [3]).
Excesses above this level are due to weak flares and quiescent active regions.
]]

== The greatest events (to the top) ==

At the top end of the GOES soft X-ray distribution, a handful of the most
extreme events had saturated the 1-8 Å readout.
Ref. [4] describes an evenhanded patching of these items, together with a
correcting for a systematic offset (Ref. [2]).
This produced a list of 37 >X10 events after background subtraction.
This basic manipulation departs from tradition, and so we provide this
[greatest flares]
catalog using the letter system "QSabcmxyz".
To translate, the new "y" class is the old "X10" class, sometimes now called
"S" (Ref. 5]), and the new catalog lists 37 of them.
The new "z" class has no examples yet (but we're hopeful), although the
[https://heliowiki.smce.nasa.gov/wiki/index.php/The_1859_Space_Weather_Event_Revisited Carrington event]
might have been in that category.

== Conclusions ==

== References ==

[1] "Sentinels of the sun: forecasting space weather," B. Poppe and K. Jorden, 2006

[2] [https://www.sciencedirect.com/science/article/pii/B9780128143278000196 "GOES-R Series Solar X-ray and Ultraviolet Irradiance"]

[3] [http://adsabs.harvard.edu/abs/2011SoSyR..45..182G "Soft X-ray variability over the present minimum of solar activity as observed by SphinX"]

[4] [https://ui.adsabs.harvard.edu/abs/2024SoPh..299...39H "The Greatest GOES Soft X-ray Flares"]

[5] [https://ui.adsabs.harvard.edu/abs/2025ApJ...979L..16T "The Occurrence of Powerful Flares Stronger than X10 Class in Solar Cycles"]

File:526f1.png

2026-05-11T18:17:13Z

Hhudson:

How Extreme Can Solar Flares Get? A Statistical View

2026-05-05T19:06:07Z

Hhudson: /* Introduction */

{{Infobox Nugget |name = Nugget
|title = How Extreme Can Solar Flares Get? A Statistical View
|number = 525
|first_author = Lapo CECCARELLI
|second_author = Daniela CASTRO-CAMILO
|publish_date = May 4, 2026
|next_nugget = TBD
|previous_nugget = {{#ask: [[Category:Nugget]] [[RHESSI Nugget Index::524]]}}
}}

== Introduction ==

Quantifying the upper limits of solar flare activity is central to
understanding
[https://heliowiki.smce.nasa.gov/wiki/index.php/Extreme_events,_stellar_evolution,_and_magnetic_reconnection space weather]
risk. In this work, we analyse the lengthy
record of soft X-ray (1-8 Å) fluxes from
[https://www.swpc.noaa.gov/products/goes-x-ray-flux GOES]
(1975-2022, see Figure 1 and Ref. [1]) through the lens of Extreme
Value Theory ([https://en.wikipedia.org/wiki/Extreme_value_theory EVT]),
focusing explicitly on the statistical structure
of the tail of the flare-intensity distribution function.
Note that a [https://heliowiki.smce.nasa.gov/wiki/index.php/How_energetic_can_solar_flares_become%3F recent Nugget]
dealt with this subject from a different observational point of view.

[[File:525f1.png|center|thumb|600px|caption|Figure 1: 
Time series of the peak flux for each solar flare event from 1975 to 2022,
W/m2 for the 1-8 Å band.
]]

== Extreme Value Modelling Framework ==

We adopt two complementary EVT approaches. First, a block maxima
framework, modeling weekly maxima using the Generalised Extreme Value
(GEV) distribution.
Second, a peaks-over-threshold (POT) approach, modeling the
exceedances above a high quantile (a specified threshold) using the
Generalised Pareto Distribution (GPD).
These approaches target the same tail behaviour but rely on different
asymptotic regimes, providing a useful consistency check.

The GPD distribution for exceedances y = X - u > 0 is defined as

[[File:525eq1.png|thumb|center|500px]]

where μ is the real-valued "location parameter", σ > 0 is the
"scale parameter", and ξ is the "shape parameter" governing the
behaviour of the tail of the distribution, i.e. the greatest values.

The GPD distribution for exceedances y = X - u > 0 is defined as:

[[File:525eq2.png|thumb|center|600px]]

where σu > 0 is the scale parameter above threshold u
and ξ is the same shape parameter controlling tail "heaviness".

A key quantity in both formulations is the shape parameter, which
governs tail heaviness. Our estimates consistently suggest a positive
shape parameter, indicating heavy-tailed behaviour and supporting
the plausibility of very large events beyond the observed range.

== Diagnostics and Model Assessment ==

We assess model adequacy using standard EVT diagnostics.
"Quantile-quantile" plots (Figure 2) show good agreement between empirical
and fitted distributions in the tail region.
"Dependence diagnostics" further highlight the role of temporal
clustering, suggesting that extreme flares may not occur independently,
an aspect that is partially accounted for through the weekly
aggregation in the GEV framework.

[[File:525f2.png|center|thumb|600px|caption|Figure 2: 
Quantile plot for the selected GEV model, where the location and
scale parameters are a smooth function of the background level and
week of the event.
]]

== Return Levels and Risk Quantification ==

[https://en.wikipedia.org/wiki/Return_period "Return level"] estimates
derived from both GEV and GPD models (Figure 3 shows results for
the GEV model) provide a quantitative interpretation of extreme
flare magnitudes. Extrapolation indicates that
[https://heliowiki.smce.nasa.gov/wiki/index.php/The_1859_Space_Weather_Event_Revisited Carrington]-like
events correspond to return periods on the order of a century, while
more extreme scenarios remain within the support of the fitted
heavy-tailed models. Importantly, uncertainty increases rapidly
with the return period, as reflected in widening confidence intervals.
This highlights the intrinsic difficulty of inference in the far
tail, even with several decades of satellite data.

[[File:525f3.png|center|thumb|600px|caption|Figure 3: 
Return Level plot for the selected GEV model. The horizontal dashed
line corresponds to the estimated magnitude of the
[https://heliowiki.smce.nasa.gov/wiki/index.php/The_1859_Space_Weather_Event_Revisited Carrington event],
while the vertical ones represent the 95% confidence interval for
its return period.
]]

== Implications for Solar Physics ==

From a statistical perspective, the results reinforce that assumptions
about the nature of the tail
are critical when extrapolating beyond observed data.
The consistency we find between GEV and GPD approaches strengthens confidence
in the inferred tail behaviour, while also emphasising the limits
of data-driven extrapolation.

== Limitations and Future Directions ==

While the GEV and GPD models provide principled and asymptotically
justified frameworks for modelling extremes, their adequacy is limited
in settings where events are irregularly spaced and potentially
dependent, as is the case for solar flares.
[https://en.wikipedia.org/wiki/Point_process "Point-process"] approaches,
such as the Hawkes self-exciting processes, offer a natural way to
capture temporal clustering and triggering mechanisms. Combining
such models with EVT for the flare magnitudes represents a promising
direction for more realistic and physically informed modelling of
extreme solar activity

== References ==

[1] [https://ui.adsabs.harvard.edu/abs/2024SoPh..299...39H "The Greatest GOES Soft X-ray Flares"]

SolarNuggets

2026-05-05T13:27:45Z

Hhudson:

Welcome to the [[SolarNuggets]] collection, which extends the series of [[RHESSI]] Nuggets. The following is a time-ordered list of the latest Nuggets added to the HelioWiki. An [[:Category:Nugget|alphabetical list of the SolarNuggets]] is also available as well as [[:Category:RHESSI Nugget List|yearly lists]]. One can search on author, topic, IAU flare identifier, etc.). We welcome volunteer authors - please see our page of [[Help:For_Authors| help for authors]] or just send an email to the Curator at (hugh.hudson@glasgow.ac.uk).

{{Nugget Badge
|title = How Extreme Can Solar Flares Get? A Statistical View‎‎
|number = 525
|first_author = Lapo Ceccarelli
|second_author = and Daniela CASTRO-CAMILO
||publish_date = 4 May 2026
|description = A proper statistical treatment of the prospects for an extreme solar flare event
|image=Icon525.png}}

{{Nugget Badge
|title = Observations of Slow Elemental Abundance Decay in Association to CME
|number = 524
|first_author = Saara TAKALA
||publish_date = 27 April 2026
|description = Soft X-ray spectroscopy tracks coronal abundance variations associated with a CME
|image=Icon524.png}}

{{Nugget Badge
|title = An Unusual Long-Lived Radio Burst Oscillating in Frequency
|number = 523
|first_author = Marian KARLICKÝ,
|second_author = Robert SYCH and Alena ZEMANOVÁ
||publish_date = 20 April 2026
|description = Remarkable decimetric signatures of structured outflows from a flaring active region
|image=Icon523.png}}

{{Nugget Badge
|title = Lateral Deformation of Large-scale Coronal Mass Ejections during the Transition from Nonradial to Radial Propagation
|number = 522
|first_author = Huidong HU
||publish_date = 13 April 2026
|description = Coronal mass ejections can begin their trajectory highly tilted to the vertical, but then straighten out
|image=Icon522.png}}

{{Nugget Badge
|title = Can EUV Power-Spectral Indices Reveal Imminent Solar Flares?
|number = 521
|first_author = Sihui ZHONG,
|second_author = Dmitrii KOLOTKOV and Valery M. NAKARIAKOV
||publish_date = 6 April 2026
|description = A new flare-precursor observable - power spectra
|image=Icon521.png}}

{{Nugget Badge
|title = How energetic can solar flares become?
|number = 520
|first_author = Natalie KRIVOVA
||publish_date = 31 March 2026
|description = The history of active-region areas suggests the possibility of solar superflares
|image=Icon520.png}}

{{Nugget Badge
|title = Hinode EIS Observations of Plasma Composition Evolution and Radiative Cooling of Flare Loops
|number = 519
|first_author = Teodora MIHĂILESCU,
|second_author = Peter YOUNG et AL.
||publish_date = 16 March 2026
|description = Higher FIP bias than expected in some flare loops, a diagnostically interesting result
|image=Icon519.png}}

{{Nugget Badge
|title = When Magnetic Field Lines Stretch, Snap, and Expand: A New Look at Solar Flares with L-maps
|number = 518
|first_author = Maria KAZACHENKO,
|second_author = Yuhong FAN and Andrey AFANASYEV
||publish_date = 9 March 2026
|description = A clever new tool tracks magnetic connectivity (and energy) during flare/CME occurrence
|image=Icon518.png}}

{{Nugget Badge
|title = Observational Evidence Linking Loop Length and Thermal/Nonthermal Peak Timing in Solar Flares
|number = 517
|first_author = Solomon PERRIYIL
||publish_date = 23 February 2026
|description = Clear evidence for the universality of the physics behind the Neupert Effect
|image=Icon517.png}}

{{Nugget Badge
|title = A fine-scale bright kernel captured by Hi-C 3 in the post-maximum phase of an M-class solar flare
|number = 516
|first_author = Sanjiv TIWARI
||publish_date = 9 February 2026
|description = The Hi-C rocket catches an extremely compact brightening in late-phase flare ribbon development
|image=Icon516.png}}

{{Nugget Badge
|title = On the Relationship Between Nanoflare Energy and Delay in the Closed Solar Corona
|number = 515
|first_author = Shanwlee SOW MONDAL et al.
||publish_date = 19 January 2026
|description = Nanoflaring implies energy storage and sudden release, suggesting correlation between event energy and its timing
|image=Icon515.png}}

{{Nugget Badge
|title = Fine structures in solar flare ribbons
|number = 514
|first_author = Jonas THOEN FABER
||publish_date = 12 January 2026
|description = Elongated "riblets" commonly rise out of flare ribbons, and have characteristic Doppler shifts
|image=Icon514.png}}

{{Nugget Badge
|title = The M- and X-class White-light Flares in Super Active Region NOAA 13664/13697
|number = 513
|first_author = Zhichen JING
|second_author = and Ying LI
|publish_date = 5 January 2026
|description = "Super" active regions have relatively more frequent X-class flares, which correlate well with visible continuum (white-light flare) emission
|image=Icon513.png}}

{{Nugget Badge
|title = Iron Fluorescence in X-class Solar Flares
|number = 512
|first_author = Abhilash SARWADE
|publish_date = 8 December 2025
|description = A new spectroscopic capability for Iron K-alpha fluorescence
|image=Icon512.png}}

{{Nugget Badge
|title = Sun-as-a-star Analysis of a Solar Eruption Source Region Using H-alpha Spectroscopic Observations from CHASE
|number = 510
|first_author = Xiaofeng LIU
|second_author = and Yijun HOU
|publish_date = 24 November 2025
|description = Sun-as-a-star observations help to translate solar/stellar processes
|image=Icon5010.png}}

{{Nugget Badge
|title = On the Origin of Solar Long-Duration Gamma-Ray Flares‎‎‎‎
|number = 509
|first_author = Alessandro BRUNO
|publish_date = 3 November 2025
|description = Do we really need a CME to produce a long-duration solar gamma-ray event?
|image=Icon509.png}}

{{Nugget Badge
|title = FAI and GOES eclipses‎‎
|number = 508
|first_author = Hugh HUDSON
|publish_date = 20 October 2025
|description = Flare anticipation via FAI may have problems during GOES eclipses, which are really interesting in their own right
|image=Icon508.png}}

{{Nugget Badge
|title = The EUV Late Phase‎
|number = 507
|first_author = Sascha ORNIG
|publish_date = 13 October 2025
|description = Basic comparative statistics of the ELP, a distinct flare phenomenon
|image=Icon507.png}}

{{Nugget Badge
|title = Time evolution of flare-accelerated electrons using the warm-target model‎
|number = 506
|first_author = Debesh BHATTACHARJEE
|publish_date = 6 October 2025
|description = Considering a "warm" thick target allows flare-accelerated electrons to be treated self-consistently
|image=Icon506.png}}

{{Nugget Badge
|title = SOLSTICE observes flare Doppler shifts in Si III
|number = 505
|first_author = Luke MAJURY
|publish_date = 30 September 2025
|description = A rarely used database suggests prograde-flow Doppler shifts in flaring plasmas
|image=Icon505.png}}

{{Nugget Badge
|title = Flare Phases and the Earth's Ionospheric Response
|number = 504
|first_author = Susanna BEKKER
|publish_date = 16 September 2025
|description = A flare's "EUV late phase" is surprisingly geoeffective
|image=Icon504.png}}

{{Nugget Badge
|title = Neupertianity
|number = 503
|first_author = Hugh HUDSON
|publish_date = 25 August 2025
|description = It's hard to avoid the Neupert Effect
|image=Icon503.png}}

{{Nugget Badge
|title = Synchrotron Radiation and the Foundations for a Cosmic Bridge
|number = 502
|first_author = Immanuel JEBARAJ
|publish_date = 11 August 2025
|description = Gyrosynchrotron radiation in shocks: a cosmic connection
|image=Icon502.png}}

{{Nugget Badge
|title = The Aulanier Effect: drifting footpoints of CME flux ropes
|number = 501
|first_author = Jaroslav DUDÍK,
|second_author = Juraj LÖRINČÍK and Brigitte SCHMIEDER
|publish_date = 21 July 2025
|description = The breakthrough to 3D flare physics: the Aulanier Effect
|image=Icon501.png}}

{{Nugget Badge
|title = Five Hundred Nuggets
|number = 500
|first_author = Hugh HUDSON
|publish_date = 14 July 2025
|description = A milestone
|image=Icon169.png}}

{{Nugget Badge
|title = Quasiperiodic Pulsations in the Balmer Continuum in an X-class Solar White-light Flare
|number = 499
|first_author = De-Chao SONG et al.
|publish_date = 30 June 2025
|description = QPP in the Balmer continuum: the powerful heartbeat of a flare
|image=Icon499.png}}

{{Nugget Badge
|title = High-Resolution Observations of a C3 class White-Light Flare
|number = 498
|first_author = Zhe XU and
|second_author = Xiaoli YAN
|publish_date = 16 June 2025
|description = A compact white-light flare with vortical motions (and hard X-rays)
|image=Icon498.png}}

{{Nugget Badge
|title = The Sun's open-closed flux boundary and the origin of the slow solar wind
|number = 497
|first_author = Chloe WILKINS and
|second_author = David PONTIN
|publish_date = 26 May 2025
|description = Identifying the solar sources of slow solar wind
|image=Icon497.png}}

{{Nugget Badge
|title = Delay of Near-Relativistic Electrons
|number = 496
|first_author = Grant MITCHELL
|publish_date = 19 May 2025
|description = Parker Solar Probe solves an old mystery about type III bursts
|image=Icon496.png}}

{{Nugget Badge
|title = A Multi-Site Telescope for Multi-Height for Synoptic Observations
|number = 495
|first_author = Fallon KONOW
|publish_date = 11 May 2025
|description = A new synoptic network for observations at multiple wavelengths
|image=Icon495.png}}

{{Nugget Badge
|title = On turbulent magnetic reconnection: fast and slow mean steady-states
|number = 494
|first_author = Sage STANISH
|second_author = and David MacTAGGART
|publish_date = 28 April 2025
|description = In a turbulent medium, magnetic reconnection has two limiting domains
|image=Icon494.png}}

{{Nugget Badge
|title = Quasi-Periodic Pulsations in Ionospheric TEC and Flare EUV
|number = 493
|first_author = Aisling O'HARE
|publish_date = 21 April 2025
|description = The Earth's ionosphere reflects QPPs, with a small delay
|image=Icon493.png}}

{{Nugget Badge
|title = Metis observations of Alfvenic outflows driven by interchange reconnection in a pseudostreamer
|number = 492
|first_author = Paolo ROMANO and the Metis team
|publish_date = 7 April 2025
|description = Exactly as predicted by numerical simulations... a rare coup
|image=Icon492.png}}

{{Nugget Badge
|title = Solar Rollercoaster: looping-the-loop in the solar corona
|number = 491
|first_author = Mohamed NEDAL et al.
|publish_date = 31 March 2025
|description = Large-scale helical motion in the flare/CME SOL2024-05-14
|image=Icon491.png}}

{{Nugget Badge
|title = Proton Beam Energy Deposition as a Mechanism of Deep Photospheric Heating
|number = 490
|first_author = Samuel GRANOVSKY
|second_author = and Alexander KOSOVICHEV
|publish_date = 17 March 2025
|description = Evidence for proton beams in white-light flares
|image=Icon490.png}}

{{Nugget Badge
|title = New insights into the proton precipitation sites in solar flares
|number = 489
|first_author = Andrea Francesco BATTAGLIA
|second_author = and Säm KRUCKER
|publish_date = 17 February 2025
|description = There is no detectable difference in proton and electron foopoint locations after all
|image=Icon489.png}}

{{Nugget Badge
|title = Solar Gamma-Ray Evidence for a Distinct Population of MeV Flare-Accelerated Electrons
|number = 488
|first_author = Gerry SHARE
|second_author =
|publish_date = 10 February 2025
|description = Relativistic electrons in solar flares newly recognized as a distinct process
|image=Icon488.png}}

{{Nugget Badge
|title = From Chromospheric Evaporation to Coronal Rain: An Investigation of the Mass and Energy Cycle of a Flare‎
|number = 487
|first_author = Seray &Scedil;AHIN
|second_author = and Patrick ANTOLIN
|publish_date = 3 February 2025
|description = A first quantitative comparison of flare evaporation and coronal rain
|image=Icon487.png}}

{{Nugget Badge
|title = Energetic neutral atoms detected in the large solar energetic particle event of February 2022‎
|number = 486
|first_author = Christina COHEN
|second_author =
|publish_date = 20 January 2025
|description = Only the second direct observation of high-energy neutral atoms from the Sun
|image=Icon486.png}}

{{Nugget Badge
|title = Magnetic topology of quiet-Sun Ellerman bombs and associated ultraviolet brightenings‎
|number = 485
|first_author = Aditi BHATNAGAR
|second_author =
|publish_date = 6 January 2025
|description = Tiny "Ellerman Bombs" occur all across the solar surface, with differences
|image=Icon485.png}}

{{Nugget Badge
|title = Unveiling CME Dynamics: Rare Rotations of CMEs in the Heliosphere
|number = 484
|first_author = Sandeep KUMAR and
|second_author = Nandita SRIVASTAVA
|publish_date = 30 December 2024
|description = CMEs usually do not show additional rotation as they move though the heliosphere
|image=Icon484.png}}

{{Nugget Badge
|title = Spatial and Spectral Evolution of Microwave and X-Ray Sources During the Limb Flare SOL2023-02-05
|number = 483
|first_author = Yulia N. SHAMSUTDINOVA
|publish_date = 23 December 2024
|description = Rare microwave imaging spectroscopy of a hot-onset precursor event
|image=Icon483.png}}

{{Nugget Badge
|title = High-resolution observational analysis of flare ribbon fine structures
|number = 482
|first_author = Jonas THOEN FABER
|publish_date = 16 December 2024
|description = Spatially periodic fine structures in flare ribbons reveal current-sheet tearing
|image=Icon482.png}}

{{Nugget Badge
|title = Advection and super-diffusive expansion as the model of flare accelerated electron transport in type III solar radio bursts
|number = 481
|first_author = Eduard KONTAR
|publish_date = 9 December 2024
|description = Sturrock's dilemma resolved
|image=Icon481.png}}

{{Nugget Badge
|title = Faraday's Law in Solar Flares: A Cautionary Message
|number = 480
|first_author = Michael FARADAY
|publish_date = 2 December 2024
|description = We must not forget the global implications of Faraday's Law
|image=Icon480.png}}

{{Nugget Badge
|title = Remarkable NUV Spectrum of an M-star Megaflare
|number = 479
|first_author = Adam KOWALSKI
|publish_date = 25 November 2024
|description = Remarkable NUV spectra from an HST stellar flare
|image=Icon479.png}}

{{Nugget Badge
|title = Revised Point-Spread Functions of AIA and their effect on DEM analyses
|number = 478
|first_author =Stefan HOFMEISTER,
|second_author = Daniel Wolf SAVIN, and Michael HAHN
|publish_date = 18 November 2024
|description = Substantial revisions of the AIA point-response functions
|image=Icon478.png}}

{{Nugget Badge
|title = How much of the energy in flare-accelerated electrons reaches the chromosphere?
|number = 477
|first_author = Meriem ALAOUI
|second_author = and Gordon HOLMAN
|publish_date = 11 November 2024
|description = Keeping flare-accelerated electrons out of the chromosphere
|image=Icon477.png}}

{{Nugget Badge
|title = Spatially resolved plasma composition evolution in a solar flare
|number = 476
|first_author = Andy S. H. TO
|publish_date = 4 November 2024
|description = Reconnection outflow feeds abundance variations
|image=Icon476.png}}

{{Nugget Badge
|title = HOPE during high activity
|number = 475
|first_author = Hugh HUDSON
|second_author = and Alphonse STERLING
|publish_date = 28 October 2024
|description = Hot onsets appear even in the most active solar conditions
|image=Icon475.png}}

{{Nugget Badge
|title = Simulated heliospheric electron spectra show sensitivity to plasma properties of a source region in the flaring corona
|number = 474
|first_author = Ross PALLISTER
|second_author = and Natasha JEFFREY
|publish_date = 21 October 2024
|description = Getting closer to an understanding of how solar energetic particles "escape"
|image=Icon474.png}}

{{Nugget Badge
|title = An extremely complex active region with very strong non-neutralized electric currents
|number = 473
|first_author = Ioannis KONTOGIANNIS
|publish_date = 14 October 2024
|description = Large non-neutralized electric currents flow through the active-region corona
|image=Icon473.png}}

{{Nugget Badge
|title = An X9 flare and its huge crochet (SFE)
|number = 472
|first_author = Hugh HUDSON
|publish_date = 7 October 2024
|description = The geomagnetic effect (SFE/crochet) that will calibrate the Carrington flare
|image=Icon472.png}}

{{Nugget Badge
|title = All microflares that accelerate electrons to high energies are rooted in sunspots
|number = 471
|first_author = Andrea Francesco BATTAGLIA
|publish_date = 30 September 2024
|description = Microflares with hard X-ray spectra are a well-defined class, and invariably have one footpoint embedded in a sunspot
|image=Icon471.png}}

{{Nugget Badge
|title = The warm-target model and kappa distributions
|number = 470
|first_author = Yingjie LUO
|publish_date = 16 September 2024
|description = A self-consistent treatment of non-thermal electron spectra points to kappa distributions
|image=Icon470.png}}

{{Nugget Badge
|title = Is there HOPE for Hyder flares...
|number = 468
|first_author = Hugh HUDSON
|publish_date = 15 March 2024
|description = Filament eruptions/Hyder flares/disparitions brusques may all show HOPE
|image=Icon468.png}}

{{Nugget Badge
|title = Sun-as-a-star Analysis of the M8.7 Flare on 2022 October 2 Using H-alpha and EUV Spectra Taken by SMART/SDDI and SDO/EVE
|number = 467
|first_author = Takato OTSU
|publish_date = 19 February 2024
|description = Whole-Sun spectroscopic observations can readily detect ejecta
|image=Icon467.png}}

{{Nugget Badge
|title = Unexpected Asymmetry in GeV Emission
|number = 466
|first_author = Bruno ARSIOLI and Elena ORLANDO
|publish_date = 15 January 2024
|description = The high-energy solar gamma radiation shows inexplicable but fascinating properties
|image=Icon466.png}}

{{Nugget Badge
|title = When it rippled in one place and exploded in another
|number = 465
|first_author = Ivan ZIMOVETS
|publish_date = 25 December 2023
|description = Pulsations precede a flare, but seem unrelated
|image=Icon465.png}}

{{Nugget Badge
|title = Solar flares: evaporation and simulation‎
|number = 464
|first_author = Malcolm DRUETT
|publish_date = 18 December 2023
|description = Fitting beam electrons into multi-dimensional models
|image=Icon464.png}}

{{Nugget Badge
|title = Pre-impulsive and Impulsive Phases of the March 28, 2022 Sub-Terahertz Flare
|number = 463
|first_author = Galina G. MOTORINA
|publish_date = 11 December 2023
|description = A flare with an increasing sub-THz spectrum and sub-THZ precursor information
|image=Icon463.png}}

{{Nugget Badge
|title = Coronal Bright Points
|number = 462
|first_author = Daniel NÓBREGA-SIVERIO
|publish_date = 27 November 2023
|description = Bright EUV rowel-like structures can result from null-point reconnection
|image=Icon462.png}}

{{Nugget Badge
|title = Aurora-like Radio Emission from a Sunspot
|number = 461
|first_author = Sijie YU
|publish_date = 20 November 2023
|description = Maser action above a sunspot
|image=Icon461.png}}

{{Nugget Badge
|title = Search for a Flare Anticipation Index (FAI)
|number = 460
|first_author = Hugh HUDSON
|second_author = and Jim McTiernan
|publish_date = 13 November 2023
|description = Quantifying flare precursors on a few-minute time scale
|image=Icon460.png}}

{{Nugget Badge
|title = Bouncing motions of fast electrons using Nobeyama Radioheliograph
|number = 459
|first_author = Keitarou MATSUMOTO
|publish_date = 6 November 2023
|description = Solar evidence for conservation of second adiabatic invariant in particle motion
|image=Icon459.png}}

{{Nugget Badge
|title = Impact of nanoflare heating in the lower solar atmosphere
|number = 458
|first_author = Helle BAKKE
|publish_date = 30 October 2023
|description = The behavior of nanoflare fast electrons in Bifrost models
|image=Icon458.png}}

{{Nugget Badge
|title = Precise timing of flare footpoint sources from mid-infrared observations‎
|number = 457
|first_author = Paulo SIMÕES et al.
|publish_date = 23 October 2023
|description = Mid-IR observations at high spatial and high temporal resolution: Conjugacy
|image=Icon457.png}}

{{Nugget Badge
|title = The Greatest GOES Flares‎
|number = 456
|first_author = Hugh HUDSON
|second_author = and Ed CLIVER
|publish_date = 25 September 2023
|description = The greatest GOES events, re-analyzed, fall short of expectations
|image=Icon456.png}}

{{Nugget Badge
|title = Introducing SunSketcher
|number = 455
|first_author = Hugh HUDSON
|second_author = and Gordon EMSLIE
|publish_date = 11 September 2023
|description = Galloping towards roundup in the 2024 total solar eclipse
|image=Icon455.png}}

{{Nugget Badge
|title = TeV Gamma rays from the Quiescent Sun
|number = 454
|first_author = Mehr Un NISA
|second_author = and John BEACOM
|publish_date = 21 August 2023
|description = Solar photons at unprecedented high energies
|image=Icon454.png}}

{{Nugget Badge
|title = Temporal and Spatial Characteristics of Hard X-Ray Sources in Flare Model with Vertical Current Sheet
|number = 453
|first_author = Alexander SHABALIN, Eugenia OVCHINNIKOVA,
|second_author = and Yuri CHARIKOV
|publish_date = 7 August 2023
|description = Modeling betatron acceleration in current-sheet development.
|image=Icon453.png}}

{{Nugget Badge
|title = Spatial Distribution of Magnetic Reconnection Rate in an M6.5 Solar Flare
|number = 452
|first_author = Ju JING
|publish_date = 12 June 2023
|description = Linking hard X-rays to high-resolution images that show reconnection rates.
|image=Icon452.png}}

{{Nugget Badge
|title = Statistical study of Type III bursts and associated HXR emissions
|number = 451
|first_author = Nicole VILMER and Tomin JAMES
|publish_date = 29 May 2023
|description = Linking electron populations escaping from the Sun with those that RHESSI detects.
|image=Icon451.png}}

{{Nugget Badge
|title = Solar flare hard X-rays from the anchor points of an eruptive filament
|number = 450
|first_author = Muriel STIEFEL
|publish_date = 15 May 2023
|description = A rare "four-ribbon" flare has been detected in hard X-rays.
|image=Icon450.png}}

{{Nugget Badge
|title = Did a Solar Flare Accelerate all the Ambient Electrons in the Coronal Acceleration Region?...
|number = 449
|first_author = Gordon EMSLIE, Eduard KONTAR,
|second_author = Galina MOTORINA, and Brian DENNIS
|publish_date = 1 May 2023
|description = Considering SOL2017-09-10, probably not.
|image=Icon449.png}}

{{Nugget Badge
|title = Diagnostics of Spatially-Extended Turbulent Acceleration and Transport
|number = 448
|first_author = Morgan STORES
|publish_date = 24 April 2023
|description = Drilling down into the detailed structure of solar-flare energy release by including turbulence with particle acceleration.
|image=Icon448.png}}

{{Nugget Badge
|title = RHESSI's Re-entry
|number = 447
|first_author = Pascal SAINT-HILAIRE and
|second_author = Hugh HUDSON
|publish_date = 17 April 2023
|description = The final demise of RHESSI is this week
|image=Icon447.png}}

{{Nugget Badge
|title = A Glasgow geomagnetic observation of a solar flare
|number = 446
|first_author = Hugh HUDSON, John MALONE-LEIGH,
|second_author = Graham WOAN, and Chris OSBORNE
|publish_date = 13 March 2023
|description = Irish and Scottish geomagnetic observatories see a crochet much like that of the Carrington event
|image=Icon_446.png}}

{{{Nugget Badge
|title = Particle Acceleration in Two Coronal Jets
|number = 445
|first_author = Yixian ZHANG
|publish_date = 27 February 2023
|description = Coronal jets with hard X-ray sources at disjoint locations
|image=Icon445.png}}

{{Nugget Badge
|title = The Curious First Sunquake of Solar Cycle 25‎
|number = 444
|first_author = Alexander KOSOVICHEV
|publish_date = 13 February 2023
|description = A double whammy: two distinct sunquakes from SOL2022-05-10.
|image=Icon444.png}}

{{Nugget Badge
|title = Hard X-ray Pulsations via Gaussian Decomposition
|number = 443
|first_author = Hannah COLLIER and Laura HAYES
|publish_date = 30 January 2023
|description = Flare hard X-ray time variations decomposed objectively
|image=Icon443.png}}

{{Nugget Badge
|title = A possible coronal magnetic flare precursor
|number = 442
|first_author = Enrico LANDI
|publish_date = 16 January 2023
|description = Novel measurements of the coronal magnetic field may help with flare prediction
|image=Icon442.png}}

{{Nugget Badge
|title = A slow HOPE with microwave context
|number = 441
|first_author = Hugh HUDSON
|publish_date = 12 December 2022
|description = A new microwave facility at Chashan Observatory, and a prototypical HOPE
|image=Icon441.png}}

{{Nugget Badge
|title = Rapid variations of Si IV spectra in a flare observed by IRIS at a sub-second cadence
|number = 440
|first_author = Juraj LÖRINČÍK
|publish_date = 14 November 2022
|description = Transition-region lines in a flare have a Doppler component revealing quasi-periodic pulsations
|image=Icon440.png}}

{{Nugget Badge
|title = A Significant Sudden Ionospheric Disturbance Associated with a Massive Gamma-ray Burst
|number = 439
|first_author = Laura HAYES and Peter GALLAGHER
|publish_date = 31 October 2022
|description = A first SID observed in broad daylight, from a source far far away
|image=Icon439.png}}

{{Nugget Badge
|title = Effects of Coronal Structures on the Dynamics of the Global Coronal Wave of SOL2017-09-10‎
|number = 438
|first_author = Huidong HU, Ying D. LIU, and Bei ZHU
|publish_date = 17 October 2022
|description = The amazing global coronal wave of SOL2017-09-10 wrapped around the whole Sun, and displayed transmission and reflection at both polar coronal holes
|image=Icon438.png}}

{{Nugget Badge
|title = KW-Sun: The Konus-Wind Solar Flare Database in Hard X-Ray and Soft Gamma-Ray Ranges
|number = 437
|first_author = Alexandra LYSENKO
|publish_date = 26 September 2022
|description = An unrivaled hard X-ray and gamma-ray database is entering its third activity maximum
|image=Icon437.png}}

{{Nugget Badge
|title = First Detection of Kink Oscillations with Solar Orbiter
|number = 436
|first_author = Sihui ZHONG et al.
|publish_date = 19 September 2022
|description = SolO sees coronal oscillations as well as AIA can, and even better
|image=Icon436.png}}

{{Nugget Badge
|title = Energetic Neutral Hydrogen from Large Solar Flares
|number = 435
|first_author = Glenn MASON
|publish_date = 6 September 2022
|description = A rediscovered data treasury reveals the occurrence of many flare/CME events producing solar high-energy neutral atoms
|image=Icon435.png}}

{{Nugget Badge
|title = Fifty-year Anniversary of the First Detection of Gamma rays from a Solar Flare
|number = 434
|first_author = Jim Ryan,
|second_author = Brian Dennis, and Phil Dunphy
|publish_date = 8 August 2022
|description = The rich astrophysics of gamma-ray astronomy began with solar observations fifty years ago
|image=Icon434.png}}

{{Nugget Badge
|title = Fast Prograde Flows in Solar Active Regions
|number = 433
|first_author = Hugh HUDSON
|publish_date = 25 July 2022
|description = Unexpected, unpredicted, and not modeled yet - weird flows in hot active-region loops
|image=Icon433.png}}

{{Nugget Badge
|title = Undetected Minority-polarity Flux, Moss, and Coronal Heating
|number = 432
|first_author = Yi-Ming WANG
|publish_date = 11 July 2022
|description = There's plenty of room in "unipolar" active regions for both polarities, and there is good evidence for them
|image=Icon432.png}}

{{Nugget Badge
|title = Thermal/Nonthermal with MinXSS and RHESSI
|number = 431
|first_author = Shunsaku NAGASAWA
|publish_date = 13 June 2022
|description = Time-domain studies of improved X-ray spectra reveal a "super-hot' component
|image=Icon431.png}}

{{Nugget Badge
|title = Sun-as-a-star spectroscopic observations of the line-of-sight velocity of a solar eruption on October 28, 2021
|number = 430
|first_author = Yu XU
|second_author = and Hui TIAN
|publish_date = 30 May 2022
|description = The observation of the full 3d velocity of a CME, for an anniversary event
|image=Icon430.png}}

{{Nugget Badge
|title = Carl Størmer
|number = 429
|first_author = Hugh HUDSON
|second_author = and Lyndsay FLETCHER
|publish_date = 15 April 2022
|description = Størmer and the theory of trapping in loops
|image=Icon429.png}}

{{Nugget Badge
|title = Solar Hard X-rays with Insight
|number = 428
|first_author = Wei WANG
|second_author = and Ping ZHANG
|publish_date = 21 March 2022
|description = A spectacular limb flare introduces Insight/HXMT, a new observational resource
|image=Icon428.png}}

{{Nugget Badge
|title = Probing chromospheric current sheets using SST and ALMA co-observations
|number = 427
|first_author = João da SILVA SANTOS
|publish_date = 21 February 2022
|description = Emerging magnetic flux appears in ALMA images reflecting coronal current sheets
|image=Icon427.png}}

{{Nugget Badge
|title = A demonstration of STIX hard X-ray imaging spectroscopy capabilities for an X-class flare (SOL2021-10-28)
|number = 426
|first_author = Andrea BATTAGLIA, Hannah COLLIER,
|second_author = and Säm KRUCKER
|publish_date = 7 February 2022
|description = STIX imaging of an X-class flare marks its success
|image=Icon426.png}}

{{Nugget Badge
|title = A solar flare driven by thermal conduction observed in mid-infrared
|number = 425
|first_author = Guillermo GIMÉNEZ de CASTRO
|publish_date = 24 January 2022
|description = Strong 10-micron emission from a GOES C2 flare suggests conductive heating
|image=Icon425.png}}

{{Nugget Badge
|title = Disk Occultation of a Lopsided Sun‎
|number = 424
|first_author = Hugh HUDSON,
|second_author = Stephen WHITE and Säm KRUCKER
|publish_date = 10 January 2022
|description = Observing a spotless Sun can enable observations of the faint corona.
|image=Icon424.png}}

{{Nugget Badge
|title = Resolving two distinct thermal X-ray components in a compound solar flare
|number = 423
|first_author = Zhenjun ZHOU
|second_author = and Rui LIU
|publish_date = 28 December 2021
|description = Superhot coronal sources may be independent loop systems
|image=Icon423.png}}

{{Nugget Badge
|title = Bridging solar flares to coronal mass ejections
|number = 422
|first_author = Markus ASCHWANDEN
|publish_date = 14 December 2021
|description = The Neupert effect allows us to trace coronal mass ejections seamlessly
|image=Icon422.png}}

{{Nugget Badge
|title = The Jakimiec Diagnostic Diagram
|number = 421
|first_author = Hugh HUDSON
|publish_date = 29 November 2021
|description = The joint variation of GOES temperature and emission measure discloses new features via an old tool
|image=Icon421.png}}

{{Nugget Badge
|title = First look at ALMA/HInode/IRIS microflares
|number = 420
|first_author = Toshifumi SHIMIZU
|second_author = et al.
|publish_date = 8 November 2021
|description = High-resolution ALMA and multiwavelength observations of microflaring
|image=Icon420.png}}

{{Nugget Badge
|title = Thomson scattering near sunspots
|number = 419
|first_author = Pascal Saint-Hilaire
|second_author = et al.
|publish_date = 25 October 2021
|description = Completing the modeling of low-coronal Thomson polarimetry
|image=Icon419.png}}

{{Nugget Badge
|title = A Non-PFSS Global Coronal Model
|number = 418
|first_author = Oliver RICE
|second_author = and Anthony YEATES
|publish_date = 11 October 2021
|description = Modeling as convenient as PFSS but much more realistic
|image=Icon418.png}}

{{Nugget Badge
|title = Manifold Nonthermality
|number = 417
|first_author = Marina BATTAGLIA
|second_author = et al.
|publish_date = 27 September 2021
|description = Even weak flares involve multiple sites of non thermal activity
|image=Icon417.png}}

{{Nugget Badge
|title = X-Rays from a Type I Radio Burst
|number = 416
|first_author = R. RAMESH
|publish_date = 20 September 2021
|description = A first identification of type I radio emission with hot plasma
|image=Icon416.png}}

{{Nugget Badge
|title = Do Hot Onsets Predict Flare Magnitudes?
|number = 415
|first_author = Hugh HUDSON
|publish_date = 30 August 2021
|description = Maybe we can tell how big a flare is going to be from its initial development...
|image=Icon415.png}}

{{Nugget Badge
|title = Confined or Eruptive?
|number = 414
|first_author = Ting LI et al.
|publish_date = 16 August 2021
|description = Increased magnetic flux reduces CME eruptivity
|image=Icon414.png}}

{{Nugget Badge
|title = Impulsive and Gradual Eruptive Gamma Flares and Associated CMEs
|number = 413
|first_author = Alexey STRUMINSKY,
|second_author = Irina GRIGORIEVA and Andrei SADOVSKI
|publish_date = 19 July 2021
|description = Extreme behavior of flare/CME events explained by environment
|image=Icon373.png}}

{{Nugget Badge
|title = The Morphology of Flare Time Profiles
|number = 412
|first_author = Larisa KASHAPOVA
|second_author = et al.
|publish_date = 12 July 2021
|description = Systematic comparison of solar and stellar flaring time profiles
|image=Icon412.png}}

{{Nugget Badge
|title = Flare Pulsation and the Heliosphere
|number = 411
|first_author = Brendan CLARKE
|second_author = et al.
|publish_date = 5 July 2021
|description = Flare pulsations link closely to the distant heliosphere
|image=Icon411.png}}

{{Nugget Badge
|title = STIX, the Hard X-Ray Telescope on board Solar Orbiter
|number = 410
|first_author = Andrea Francesco BATTAGLIA
|second_author = and Säm KRUCKER
|publish_date = 28 June 2021
|description = STIX is operational and producing great data
|image=Icon410.png}}

{{Nugget Badge
|title = Nonequilibrium Ionization of Flare Plasma Observed by Hinode/EIS
|number = 409
|first_author = Shinsuke IMADA
|second_author =
|publish_date = 14 June 2021
|description = Evidence for non-equilibrium ionization in the current sheet of SOL2017-09-10
|image=Icon409.png}}

{{Nugget Badge
|title = Effects of Flares on Solar p-modes
|number = 408
|first_author = Maria-Cristina RABELLO SOARES
|second_author = and Frederic BAUDIN
|publish_date = 26 April 2021
|description = No detectable p-mode amplitude changes due to solar flares
|image=Icon408.png}}

{{Nugget Badge
|title = Subsecond Spikes in Solar Flare X-ray Flux as Seen by Fermi GBM
|number = 407
|first_author =Trevor KNUTH
|second_author = and Lindsay GLESENER
|publish_date = 19 April 2021
|description = A new analysis technique pushes hard X-ray time scales to 0.1 sec or faster
|image=Icon407.png}}

{{Nugget Badge
|title = Negative He 10830 Flare Ribbons and Non-thermal Electrons
|number = 406
|first_author = Graham KERR
|second_author =
|publish_date = 12 April 2021
|description = A 1D radiation hydrodynamics model can explain the dark leading edges of He I flare ribbons
|image=Icon406.png}}

{{Nugget Badge
|title = Tracing the sources of gradual solar energetic particle events
|number = 405
|first_author = David H. BROOKS
|second_author = and Stephanie L. YARDLEY
|publish_date = 29 March 2021
|description = Chemical abundances in SEPs suggest an origin in flare-related moss regions
|image=Icon405.png}}

{{Nugget Badge
|title = The Superflare SOL2017-09-06: from submm to mid-IR
|number = 404
|first_author = Guillermo (Guigue) GIMÉNEZ DE CASTRO
|second_author =
|publish_date = 15 March 2021
|description = Glimpsing the "missing decades" of the flare emission spectrum
|image=Icon404.png}}

{{Nugget Badge
|title = The Neupert Effect Revisited
|number = 403
|first_author = Jiong QIU
|second_author =
|publish_date = 8 March 2021
|description = Two time scales for heating individual flare strands
|image=Icon403.png}}

{{Nugget Badge
|title = FLUKA as a tool for interpreting flare gamma-rays
|number = 402
|first_author = Alec MACKINNON
|second_author =
|publish_date = 1 March 2021
|description = The nuclear physics of solar flares captured in a detailed model
|image=Icon402.png}}

{{Nugget Badge
|title = A Collective Study of 11 NuSTAR Microflares
|number = 401
|first_author = Jessie DUNCAN and
|second_author = Lindsay GLESENER
|publish_date = 22 February 2021
|description = Swarms of NuSTAR micro flares
|image=Icon401.png}}

{{{{Nugget Badge
|title = A Solar FRB
|number = 400
|first_author = Dale GARY and
|second_author = Hugh HUDSON
|publish_date = 15 February 2021
|description = A new frontier in the solar time domain
|image=Icon400.png}}

{{Nugget Badge
|title = Richard Schwartz
|number = 399
|first_author = Brian DENNIS and
|second_author = Hugh HUDSON
|publish_date = 25 January 2021
|description = Remembering a friend and colleague
|image=Icon399.jpg}}

{{Nugget Badge
|title = Observing Solar Flare X-ray Polarization with Prospective CubeSat Missions
|number = 398
|first_author = Natasha JEFFREY
|publish_date = 4 January 2021
|description = The polarization of the solar X-ray spectrum generally remains to be observed
|image=Icon398.png}}

{{Nugget Badge
|title = Solar effects in the local interstellar medium
|number = 397
|first_author = Don GURNETT and
|second_author = Hugh HUDSON
|publish_date = 14 December 2020
|description = Relativistic particle events observed _in situ_ in the interstellar medium
|image=Icon397.png}}

{{Nugget Badge
|title = Investigation of Small-Scale Energy Releases in Hard X-rays with FOXSI
|number = 396
|first_author = Subramania ATHIRAY and
|second_author = Juliana VIEVERING
|publish_date = 7 December 2020
|description = Hard X-rays and high temperatures from the feeblest microflares
|image=Icon396.png}}

{{Nugget Badge
|title = What drives impulsive coronal heating?
|number = 395
|first_author = Pradeep CHITTA
|second_author = et al.
|publish_date = 30 November 2020
|description = Impulsive footpoint emissions suggest magnetic reconnection in the chromosphere
|image=Icon395.png}}

{{Nugget Badge
|title = Probing the solar coronal heating function with slow magnetoacoustic waves
|number = 394
|first_author = Dmitrii KOLOTKOV
|second_author = et al.
|publish_date = 16 November 2020
|description = Coronal heating models meet damped slow magnetoacoustic waves
|image=Icon394.png}}

{{Nugget Badge
|title = Self-Consistent Flare Model
|number = 393
|first_author = Wenzhi RUAN
|second_author = and Rony KEPPENS
|publish_date = 2 November 2020
|description = Energy transport by fast particles made self-consistent with MHD flare modeling
|image=Icon393.png}}

{{Nugget Badge
|title = Hot Flare Onsets
|number = 392
|first_author = Hugh HUDSON
|second_author = et al.
|publish_date = 26 October 2020
|description = The initial soft X-ray temperatures of solar flares tend to be in the 10-15 MK range
|image=Icon392.png}}

{{Nugget Badge
|title = Electric Current Neutralization and Eruption
|number = 391
|first_author = Ellis AVALLONE
|second_author = and Xudong SUN
|publish_date = 19 October 2020
|description = Coronal currents without neutralizing return currents appear to
|image=Icon391.png}}

{{Nugget Badge
|title = Prediction of Solar Cycle 25
|number = 390
|first_author = Leif SVALGAARD
|second_author =
|publish_date = 5 October 2020
|description = Now we know how big the next solar maximum will be
|image=Icon390.png}}

{{Nugget Badge
|title = Flare/CME Cartoon Archive
|number = 389
|first_author = Hugh HUDSON
|second_author =
|publish_date = 27 September 2020
|description = A new edition of the Flare/CME archive, nearly a half kilotoon now
|image=Icon389.png}}

{{Nugget Badge
|title = Submerged Flare Acoustic Sources
|number = 388
|first_author = Juan Camilo BUITRAGO CASAS
|second_author = and Angel MARTÍNEZ
|publish_date = 13 September 2020
|description = Flare acoustic radiation emanates from a source _inside_ the Sun
|image=Icon388.png}}

{{Nugget Badge
|title = Circular Ribbon Flare at Microwaves
|number = 387
|first_author = Jeongwoo LEE
|second_author =
|publish_date = 31 August 2020
|description = Breakout reconnection reveals itself via microwave polarization measurements.
|image=Icon387.png}}

{{Nugget Badge
|title = Relation of Non-neutralized electric currents and the activity in active regions
|number = 386
|first_author = P. VEMAREDDY
|second_author =
|publish_date = 24 August 2020
|description = Non-neutralized coronal current systems contribute to CME eruptions
|image=Icon386.png}}

{{Nugget Badge
|title = White-light emission and photospheric magnetic field changes in flares
|number = 385
|first_author = J. Sebastián CASTELLANOS DURÁN
|second_author = and Lucia KLEINT
|publish_date = 17 August 2020
|description = There are strong correlations between white-light flare emissions and line-of-sight magnetic field changes
|image=Icon385.png}}

{{Nugget Badge
|title = Sunspot Differential Rotation in an X-class Flare
|number = 384
|first_author = Richard GRIMES,
|second_author = Balázs PINTÉR and Huw MORGAN
|publish_date = 10 August 2020
|description = Observations suggesting how the coronal tail can wag the photospheric dog
|image=Icon384.png}}

{{Nugget Badge
|title = Energy Partitioning in a Nonthermally Dominated Two-loop Solar Flare
|number = 383
|first_author = Galina MOTORINA
|second_author = et al.
|publish_date = 3 August 2020
|description = Modeling the propagation of energy via GX Simulator in an early-impulsive flare
|image=Icon383.png}}

{{Nugget Badge
|title = SOL2013-11-10 Eruptive Circular-ribbon Flare with Extended Remote Brightenings
|number = 382
|first_author = Chang LIU
|second_author = et al.
|publish_date = 31 July 2020
|description = A circular-ribbon event can launch an eruption by breaking through its separatrix dome
|image=Icon382.png}}

{{Nugget Badge
|title = Extreme-Ultraviolet Late Phase of Solar Flares
|number = 381
|first_author = Rui LIU
|second_author =
|publish_date = 22 June 2020
|description = Both arcade and circular-ribbon flares may sometimes spawn EUV late phase emission
|image=Icon381.png}}

{{Nugget Badge
|title = Energy transport by accelerated particles in the quiet solar atmosphere
|number = 380
|first_author = Lars FROGNER,
|second_author = Boris GUDIKSEN and Helle BAKKE
|publish_date = 15 June 2020
|description = A first study of non-thermal particles integrated into an MHD simulation of the solar atmosphere
|image=Icon380.png}}

{{Nugget Badge
|title = Quasi-periodic pulsations as indicators of oscillatory processes in solar flares
|number = 379
|first_author = Elena KUPRIYANOVA
|second_author = et al.
|publish_date = 11 May 2020
|description = Many, many QPPs
|image=Icon379.png}}

{{Nugget Badge
|title = Rejuvenating Solar Flare Termination Shocks as Particle Accelerators
|number = 378
|first_author = Bin CHEN
|second_author =
|publish_date = 4 May 2020
|description = At last, clear evidence for a long-predicted phenomenon
|image=Icon378.png}}

{{Nugget Badge
|title = Broad symmetrical Doppler-shifted Fe XXI line profiles
|number = 377
|first_author = Vanessa POLITO
|second_author =
|publish_date = 20 April 2020
|description = It is difficult to explain "evaporation" line profiles by superposition of unresolved flows
|image=Icon377.png}}

{{Nugget Badge
|title = Phenomena in the unusually long pre-impulsive phase of SOL2011-06-07
|number = 376
|first_author = Marian KARLICKÝ,
|second_author = Jana KA&Scaron;PAROVÁ, and Robert SYCH
|publish_date = 13 April 2020
|description = A massive and slowly-rising filament eruption reveals important new signatures of the physics
|image=Icon376.png}}

{{Nugget Badge
|title = Evidence for a Coronal Shock Wave Origin for Relativistic Protons Producing Solar Gamma-Rays and Observed by Neutron Monitors at Earth‎
|number = 375
|first_author = Athanasios KOULOUMVAKOS
|second_author = and Gerry SHARE
|publish_date = 6 April 2020
|description = Successful modeling of prolonged solar gamma-ray emissions and terrestrial ground-level cosmic-ray events
|image=Icon375.png}}

{{Nugget Badge
|title = Using overlappogram data to find hot flare plasma
|number = 374
|first_author = Louise HARRA
|
|publish_date = 23 March 2020
|description = Imaging Fe XXIV at high resolution with the EIS slot data
|image=Icon374.png}}

{{Nugget Badge
|title = SOL2017-09-04 (M5.5) 2017 as a Source of Relativistic Electrons and Protons
|number = 373
|first_author = Alexei STRUMINSKII
| (see text)
|publish_date = 16 March 2020
|description = Flare-accelerated particles, rather than SEPs, energize sustained gamma-ray emission
|image=Icon373.png}}

{{Nugget Badge
|title = Heating of the solar photosphere during a white-light flare‎
|number = 372
|first_author = Jan JURČÁK
| (see text)
|publish_date = 2 March 2020
|description = The best-ever spectrum of the flare photosphere
|image=Icon372.png}}

{{Nugget Badge
|title = A Hot Cusp-Shaped Confined Solar Flare
|number = 371
|first_author = Aaron HERNANDEZ-PEREZ
|publish_date = 24 February 2020
|description = A flare may have a prominent hot cusp with the help of any eruption
|image=Icon371.png}}

{{Nugget Badge
|title = The Temporal and Spatial Extension of Gamma-ray Emission from the Sun
|number = 370
|first_author = Nat GOPALSWAMY
|publish_date = 17 February 2020
|description = Sustained solar γ-rays and solar cosmic rays
|image=Icon370.ng.png}}

{{Nugget Badge
|title = A PSP Perihelion
|number = 369
|first_author = Jessie DUNCAN
|second_author = and Hugh Hudson
|publish_date = 20 January 2020
|description = The Parker Solar Probe enters its fourth perihelion already. Now
|image=Icon369.png}}

{{Nugget Badge
|title = Remembering John Brown
|number = 368
|first_author = Alec MacKINNON
|second_author =
|publish_date = 13 January 2020
|description = John passed away unexpectedly on 16 November 2019
|image=Icon368.png}}

{{Nugget Badge
|title = A Global Survey of EUV Coronal Power Spectra
|number = 367
|first_author = Karl Battams
|second_author =
|publish_date = 30 December 2019
|description = Time-series parameter maps of imaged power spectra from an AIA pipeline
|image=Icon367.png}}

{{Nugget Badge
|title = Cosmic Rays over the Rainbow Bridge
|number = 366
|first_author = Hugh Hudson
|second_author = Alec MacKinnon
|publish_date = 16 December 2019
|description = Cosmic rays approach the Sun
|image=Icon366.png}}

{{Nugget Badge
|title = Spectropolarimetric Insight into Plasma-Sheet Dynamics of a Solar Flare
|number = 365
|first_author = Ryan French
|second_author =
|publish_date = 9 December 2019
|description = CoMP polarization patterns in SOL2017-09-10 are amazing
|image=Icon365.png}}

{{Nugget Badge
|title = Lorentz Force Evolution Reveals the Energy Build-up Processes during Recurrent Eruptive Solar Flares‎
|number = 364
|first_author = Ranadeep Sarkar,
|second_author = Nandita Srivastava and Astrid Veronig
|publish_date = 18 November 2019
|description = The net Lorentz force clearly exhibits a build-up and release pattern
|image=Icon364.png}}

{{Nugget Badge
|title = Flare waiting times depend on their magnitudes
|number = 363
|first_author = Hugh Hudson
|second_author =
|publish_date = 11 November 2019
|description = Surprising new evidence for the flare build-up and release process
|image=Icon363.png}}

{{Nugget Badge
|title = Can magnetic reconnection cause solar rainstorms?‎
|number = 362
|first_author = Petra Kohutova
|second_author =
|publish_date = 4 November 2019
|description = Impulsive coronal heating resulting from reconnection can trigger coronal rain
|image=Icon362.png}}

{{Nugget Badge
|title = Non-radial jets on the edges of active regions
|number = 361
|first_author = Peter Wyper
|second_author =
|publish_date = 14 October 2019
|description = The very common jet structures we see can naturally combine twist and breakout
|image=Icon361.png}}

{{Nugget Badge
|title = Searching SOLfully within the Nuggets
|number = 360
|first_author = Hugh Hudson
|second_author =
|publish_date = 7 October 2019
|description = The IAU target identifier works well for finding items about a particular event
|image=Icon360.png}}

{{Nugget Badge
|title = Submillimeter Radiation as the Thermal Component of the Neupert Effect
|number = 359
|first_author = Guillermo Giménez de Castro
|second_author =
|publish_date = 31 September 2019
|description = Flare radiation at the highest frequencies can be bremsstrahlung
|image=Icon359.png}}

{{Nugget Badge
|title = The "Last Best" Flares
|number = 358
|first_author = Hugh Hudson,
|second_author = Ed Cliver, and Brian Dennis
|publish_date = 24 September 2019
|description = Major flares tend to happen at the very ends of sunspot cycles
|image=Icon358.png}}

{{Nugget Badge
|title = Dynamic Processes of the Moreton Wave on 2014 March 29‎
|number = 357
|first_author = Denis Cabezas
|second_author = and the FMT team
|publish_date = 16 September 2019
|description = A beautiful Moreton wave excited by the best-observed flare ever
|image=Icon357.png}}

{{Nugget Badge
|title = EVE-RHESSI DEM Models and the Low-energy Cutoff for Nonthermal Electrons
|number = 356
|first_author = Jim McTiernan
|second_author =
|publish_date = 9 September 2019
|description = Characterizing flare temperature distributions helps to define the non-thermal energy release
|image=Icon356.png}}

{{Nugget Badge
|title = Stealth Coronal Mass Ejections from Active Regions
|number = 355
|first_author = Jennifer O'Kane
|second_author =
|publish_date = 26 August 2019
|description = Perhaps just feeble versions of the same magnetic disease...
|image=Icon355.png}}

{{Nugget Badge
|title = Do Kepler Superflare Stars Really Include Slowly Rotating Sun-like Stars?‎
|number = 354
|first_author = Yuta NOTSU
|second_author =
|publish_date = 15 July 2019
|description = Kepler superflares hint at solar superflares
|image=Icon354.png}}

{{Nugget Badge
|title = Localized Microwave and EUV Bright Structures in an Eruptive Prominence
|number = 353
|first_author = Jing HUANG
|second_author =
|publish_date = 22 June 2019
|description = Detailed correlations between EUV and microwaves in prominence fine structures
|image=Icon353.png}}

{{Nugget Badge
|title = Broken-up hard X-ray spectra found for a loop-top source during a solar limb flare
|number = 352
|first_author = Hao NING,
|second_author = Yao CHEN and Jeongwoo LEE
|publish_date = 16 June 2019
|description = SOL2017-09-10 coronal hard X-ray sources
|image=Icon352.png}}

{{Nugget Badge
|title = The Cosmic-Ray Shadow and Coronal Magnetism
|number = 351
|first_author = Frederik Tenholt
|second_author =
|publish_date = 27 May 2019
|description = The coronal magnetic field measured in Antarctica
|image=Icon351.png}}

{{Nugget Badge
|title = Kristian Birkeland
|number = 350
|first_author = Hugh HUDSON
|second_author = and Lyndsay FLETCHER
|publish_date = 6 May 2019
|description = Space weather a century ago: Kristian Birkeland
|image=Icon350.png}}

{{Nugget Badge
|title = Warm UV loops heated by small-scale cancellation events
|number = 349
|first_author = Seray ŞAHIN
|second_author = and Vasyl YURCHYSHYN
|publish_date = 22 April 2019
|description = Precisely locating the footpoints of warm coronal loops helps identify their source(s) of excitation
|image=Icon349.png}}

{{Nugget Badge
|title = Multiple Regions of Shock-accelerated Particles during a Solar Coronal Mass Ejection
|number = 348
|first_author = Diana MOROSAN
|second_author =
|publish_date = 1 April 2019
|description = LOFAR identifies herringbone sources within the flank of the SOL2017-09-10 shock - no joke
|image=Icon348.png}}

{{Nugget Badge
|title = Persistent Quasi-Periodic Pulsations Detected During the Large X8.2 Solar Flare
|number = 347
|first_author = Laura HAYES
|second_author = and Peter GALLAGHER
|publish_date = 25 March 2019
|description = The most beautiful flare has the most beautiful pulsations
|image=Icon347.png}}

{{Nugget Badge
|title = Is the coronal magnetic field braiding?
|number = 346
|first_author = Markus ASCHWANDEN
|second_author =
|publish_date = 11 March 2019
|description = This iconic cartoon does not relate well to the observations
|image=Icon346.png}}

{{Nugget Badge
|title = An energetic pre-flare: electron distributions in magnetic reconnection outflows
|number = 345
|first_author = Marina BATTAGLIA,
|second_author = Eduard KONTAR and Galina MOTORINA
|publish_date = 18 February 2019
|description = Assessing energy partition in a pre-impulsive flare development
|image=Icon345.png}}

{{Nugget Badge
|title = Linear Polarization in H-alpha Flares
|number = 344
|first_author = Tomoko KAWATE
|second_author = and Yoichiro HANAOKA
|publish_date = 4 February 2019
|description = H-alpha polarization is rarely observable but, in once case, very suggestive
|image=Icon344.png}}

{{Nugget Badge
|title = Short-Period Waves
|number = 343
|first_author = Sijie YU
|second_author = and Bin CHEN
|publish_date = 21 January 2019
|description = New decimetric imaging spectroscopy suggests Alfvénic energy transport in flares
|image=Icon343.png}}

{{Nugget Badge
|title = The Interesting RHESSI/SAS Archive
|number = 342
|first_author = Hugh HUDSON
|second_author = and Martin FIVIAN
|publish_date = 8 January 2019
|description = The full mission database shows RHESSI to have been very stable geometrically
|image=Icon342.png}}

{{Nugget Badge
|title = Homologous White Light Solar Flares‎
|number = 341
|first_author = Paolo ROMANO
|second_author = and Abouazza ELMHAMDI
|publish_date = 31 December 2018
|description = Homologous white-light flares, in rapid succession, and coronal null points
|image=Icon341.png}}

{{Nugget Badge
|title = The flight of FOXSI-3
|number = 340
|first_author = Lindsay GLESENER
|second_author = and Noriyuki NARUKAGE
|publish_date = 10 December 2018
|description = Single-photon counting and direct focusing across hard and soft energies
|image=Icon340.png}}

{{Nugget Badge
|title = Stellar Flares and Starspots
|number = 339
|first_author = Lauren DOYLE
|second_author =
|publish_date = 3 December 2018
|description = Stellar flares don't spatially match their starspots
|image=Icon339.png}}

{{Nugget Badge
|title = Neutron Production in Solar Flares
|number = 338
|first_author = Ron MURPHY
|second_author = and Gerry SHARE
|publish_date = 26 November 2018
|description = Neutron astronomy helps us understand solar flares
|image=Icon338.png}}

{{Nugget Badge
|title = Cycle 25 Strikes Again
|number = 337
|first_author = Kamil BICZ
|second_author =
|publish_date = 20 November 2018
|description = A second, larger Cycle 25 sunspot
|image=Icon337.png}}

{{Nugget Badge
|title = Remembering Marcos Machado via his research
|number = 336
|first_author = Hugh HUDSON
|second_author =
|publish_date = 13 November 2018
|description = Recalling a friend and colleague, and admiring his final paper
|image=Icon336.png}}

{{Nugget Badge
|title = CORONAS/SPIRIT Mg XII and Nanoflares‎
|number = 335
|first_author = Anton REVA
|second_author =
|publish_date = 22 October 2018
|description = Monochromatic Mg XII spectroheliography sets severe limits on nanoflare heating models
|image=Icon335.png}}

{{Nugget Badge
|title = White-light Emission and Non-thermal Electrons‎
|number = 334
|first_author = Kyoung-Sun LEE
|second_author =
|publish_date = 8 October 2018
|description = An intimate relationship between accelerated electrons and visible flare continuum
|image=Icon334.png}}

{{Nugget Badge
|title = Coronal Hard X-ray Sources Revisited
|number = 333
|first_author = Brian DENNIS
|second_author =
|publish_date = 24 September 2018
|description = Reporting some over-interpretation of the evidence for "coronal thick targets"
|image=Icon333.png}}

{{Nugget Badge
|title = Photospheric response to a flare
|number = 332
|first_author = Mike WHEATLAND
|second_author =
|publish_date = 17 September 2018
|description = Sudden changes in the magnetic field in the low atmosphere associated with particle acceleration
|image=Icon332.png}}

{{Nugget Badge
|title = New Views of Global Solar Magnetic Field Evolution Over Four Solar Cycles
|number = 331
|first_author = David WEBB
|second_author =
|publish_date = 27 August 2018
|description = A digital archive of Pat McIntosh's 44 years of solar synoptic observations
|image=Icon331.png}}

{{Nugget Badge
|title = Understanding the co-spatial return current in solar flares
|number = 330
|first_author = Meriem ALAOUI
|second_author = and Gordon HOLMAN
|publish_date = 6 August 2018
|description = Completing the circuit in a thick-target model
|image=Icon330.png}}

{{Nugget Badge
|title = 3D Magnetic Reconnection at a Coronal Null Point
|number = 329
|first_author = Shane MALONEY,
|second_author = Aidan O'Flannagain and Peter Gallagher
|publish_date = 30 July 2018
|description = Large-scale reconnection involved in Type I radio noise storm
|image=Icon329.png}}

{{Nugget Badge
|title = The true dawn of multimessenger astronomy
|number = 328
|first_author = Hugh Hudson
|second_author =
|publish_date = 23 July 2018
|description = Ever since the Carrington flare
|image=Icon328.png}}

{{Nugget Badge
|title = Microwave Imaging Spectroscopy of Flares is Here‎
|number = 327
|first_author = Dale E. Gary,
|second_author = EOVSA and RHESSI Teams
|publish_date = 16 July 2018
|description = Microwave imaging spectroscopy takes a giant leap forward with SOL2017-09-10
|image=Icon327.png}}

{{Nugget Badge
|title = Coronal nanoflares powered by footpoint reconnection
|number = 326
|first_author = Pradeep Chitta,
|second_author = Hardi Peter, and Sami Solanki
|publish_date = 9 July 2018
|description = Coronal nanoflares in active region cores can be powered by the magnetic reconnection in the lower solar atmosphere
|image=Icon326.png}}

{{Nugget Badge
|title = A remarkable, but confused, coronal hard X-ray source
|number = 325
|first_author = Alexandra Lysenko,
|second_author = Larisa Kashapova and Hugh Hudson
|publish_date = 25 June 2018
|description = A remarkable flare in 1999 adds to our short list of extended coronal hard X-ray/microwave sources
|image=Icon325.png}}

{{Nugget Badge
|title = Understanding HMI pseudocontinuum in white-light flares‎
|number = 324
|first_author = Michal &Scaron;vanda
|second_author = et al.
|publish_date = 28 May 2018
|description = The HMI pseudocontinuum (Ic) is ill-calibrated in regions with strong fields, i.e. for white-light flares
|image=Icon324.png}}

{{Nugget Badge
|title = To beam or not to beam - that is (still) the question
|number = 323
|first_author = Paulo Simões
|second_author = and Hugh Hudson
|publish_date = 14 May 2018
|description = Descriptions of the lower solar atmosphere of flares ca. Cycle 21 sound surprisingly current
|image=Icon323.png}}

{{Nugget Badge
|title = Observation of Cosmic Ray Spallation Events from SoHO‎
|number = 322
|first_author = Serge Koutchmy
|second_author = and Ehsan Tavabi
|publish_date = 7 May 2018
|description = LASCO's images capture high-energy nuclear interactions from cosmic-ray hits
|image=Icon322.png}}

{{Nugget Badge
|title = A Sunspot from Cycle 25 for sure
|number = 321
|first_author = Tomek Mrozek
|second_author = and Hugh Hudson
|publish_date = 10 April 2018
|description = YES! Cycle 25 is here!
|image=Icon321.png}}

{{Nugget Badge
|title = Blue-wing enhancement of the Mg II h and k lines in a flare
|number = 320
|first_author = Akiko TEI
|second_author =
|publish_date = 9 April 2018
|description = Flare loops involve a cool upflow preceding the hot evaporation flow
|image=Icon320.png}}

{{Nugget Badge
|title = NuSTAR detects X-ray flares in the quiet Sun
|number = 319
|first_author = Matej Kuhar
|second_author = and Säm Krucker
|publish_date = 26 March 2018
|description = Quiet-Sun flares may not be powerful, but they look a lot like ordinary flares
|image=Icon319.png}}

{{Nugget Badge
|title = Homologous CME/flares from AR 12371
|number = 318
|first_author = Panditi Vemareddy
|second_author = and Pascal Demoulín
|publish_date = 19 March 2018
|description = An excellent set of homologous flare/CMEs analyzed and explained
|image=Icon318.png}}

{{Nugget Badge
|title = Non-Maxwellian Diagnostics from SDO/EVE Spectra of an X-class Flare
|number = 317
|first_author = Elena Dzifčáková
|second_author = and Jaroslav Dudík
|publish_date = 16 February 2018
|description = Ratios of high-excitation ions can readily detect κ-distributions in flare plasmas
|image=Icon317.png}}

{{Nugget Badge
|title = Joint MinXSS and RHESSI Flare X-ray Spectra between 1 and 15 keV
|number = 316
|first_author = Chris Moore, Brian Dennis and the MinXSS Science Team
|publish_date = 5 February 2018
|description = MinXSS adds systematic views of flare soft X-ray spectra to RHESSI imagery
|image=Icon316.png}}

{{Nugget Badge
|title = Parameterized Flare Models with Chromospheric Compressions
|number = 315
|first_author = Adam Kowalski & Joel Allred
|publish_date = 17 January 2018
|description = A new approach to modeling the lower flare atmosphere
|image=FlareModelsKowalskiAllred.png}}

{{Nugget Badge
|title = A Curious Sunspot Group in 2018
|number = 314
|first_author = Hugh Hudson
|publish_date = 14 January 2018
|description = The first new sunspot group of 2018 emerged at the wrong latitude
|image = Icon314.png}}

{{Nugget Badge
|title = Tecumseh's Eclipse and Astrophysics
|number = 313
|first_author = Hugh Hudson
|publish_date = 25 December 2017
|description = The solar corona was first recognized as such, and named, in an eclipse of 1806
|image = Icon313.png}}

{{Nugget Badge
|title = Hunting for Hidden Tiny Flares
|number = 312
|first_author = Shin-nosuke ISHIKAWA
|publish_date = 27 November 2017
|description = FOXSI-2 says that episodic energy releases are still viable as a part of the coronal heating problem.
|image = Icon312.png}}

{{Nugget Badge
|title = Unusual Type III Burst Dynamics Produced by Diverging Magnetic Fields
|number = 311
|first_author = Patrick McCauley
|publish_date = 20 November 2017
|description = Unusual type III bursts follow coronal separatrix structures.
|image = Icon311.png}}

{{Nugget Badge
|title = Valderrama in the 21st Century
|number = 310
|first_author = Hugh Hudson
|publish_date = 31 October 2017
|description = A newly-described white-light flare from the 19th century!..
|image = Icon310.png}}

{{Nugget Badge
|title = Electron Scattering in the Flaring Corona
|number = 309
|first_author = Sophie Musset
|publish_date = 24 October 2017
|description = Diffusive transport may contribute to the trapping of electrons in coronal X-ray sources
|image = Icon309.png}}

{{Nugget Badge
|title = The Power of Turbulence
|number = 308
|first_author = Nic Bian
|publish_date = 25 September 2017
|description = Turbulent energy content may underlie flare energy transfer, magnetic reconnection, and particle acceleration
|image = Icon308.png}}

{{Nugget Badge
|title = The Kelvin Force and Loop-Top Concentration
|number = 307
|first_author = Kiyoto SHIBASAKI
|publish_date = 18 September 2017
|description = New physics can explain the perplexing overpressure at the flare looptop regions
|image = Icon307.png}}

{{Nugget Badge
|title = The Last Best Flare of Cycle 24?
|number = 306
|first_author = Säm Krucker
|second_author = and Hugh Hudson
|publish_date = 11 September 2017
|description = Right on schedule, Cycle 24 has produced a great flare (with a GLE)
|image = Icon306.png}}

{{Nugget Badge
|title = Electric Current Neutralization and Solar Eruption in Active Regions
|number = 305
|first_author = Yang LIU
|second_author =
|publish_date = 28 August 2017
|description = Active current systems in the solar corona don't have return currents
|image = Icon305.png}}

{{Nugget Badge
|title = RHESSI and the Megamovie
|number = 304
|first_author = Hugh Hudson, Laura Peticolas,
|second_author = and Juan Carlos Martínez Oliveros
|publish_date = 31 July 2017
|description = A wholly new way to view a solar eclipse, and to do solar astrometry
|image = Icon304.png}}

{{Nugget Badge
|title = Bastille Day 2017
|number = 303
|first_author = Hugh Hudson
|second_author = and Säm Krucker
|publish_date = 24 July 2017
|description = Interesting flares really do happen on Bastille Day...
|image = Icon303.png}}

{{Nugget Badge
|title = The Solar X-ray Limb III
|number = 302
|first_author = Marina Battaglia
|second_author = and Gordon Hurford
|publish_date = 12 June 2017
|description = RHESSI succeeds with a wholly new way to measure the solar diameter
|image = Icon302.png}}

{{Nugget Badge
|title = Double Coronal X-ray and Microwave Sources Associated With A Magnetic Breakout Solar Eruption
|number = 301
|first_author = Yao CHEN
|second_author =
|publish_date = 29 May 2017
|description = A different explanation of the double coronal hard X-ray sources
|image = Icon301.png}}

{{Nugget Badge
|title = A Lasso Model for Solar Gamma-ray Events
|number = 300
|first_author = Hugh Hudson
|second_author =
|publish_date = 15 May 2017
|description = A toy model hoping to explain the SEP/LAT relationship
|image = Icon300.png}}

[[RHESSI Science Nuggets 200 to 299|Next Nuggets]]

SolarNuggets

2026-05-05T13:26:51Z

Hhudson: Added No. 525

Welcome to the [[SolarNuggets]] collection, which extends the series of [[RHESSI]] Nuggets. The following is a time-ordered list of the latest Nuggets added to the HelioWiki. An [[:Category:Nugget|alphabetical list of the SolarNuggets]] is also available as well as [[:Category:RHESSI Nugget List|yearly lists]]. One can search on author, topic, IAU flare identifier, etc.). We welcome volunteer authors - please see our page of [[Help:For_Authors| help for authors]] or just send an email to the Curator at (hugh.hudson@glasgow.ac.uk).

{{Nugget Badge
|title = How Extreme Can Solar Flares Get? A Statistical View‎‎
|number = 525
|first_author = Lapo Ceccarelli
|second_author = Daniela CASTRO-CAMILO
||publish_date = 4 May 2026
|description = A proper statistical treatment of the prospects for an extreme solar flare event
|image=Icon525.png}}

{{Nugget Badge
|title = Observations of Slow Elemental Abundance Decay in Association to CME
|number = 524
|first_author = Saara TAKALA
||publish_date = 27 April 2026
|description = Soft X-ray spectroscopy tracks coronal abundance variations associated with a CME
|image=Icon524.png}}

{{Nugget Badge
|title = An Unusual Long-Lived Radio Burst Oscillating in Frequency
|number = 523
|first_author = Marian KARLICKÝ,
|second_author = Robert SYCH and Alena ZEMANOVÁ
||publish_date = 20 April 2026
|description = Remarkable decimetric signatures of structured outflows from a flaring active region
|image=Icon523.png}}

{{Nugget Badge
|title = Lateral Deformation of Large-scale Coronal Mass Ejections during the Transition from Nonradial to Radial Propagation
|number = 522
|first_author = Huidong HU
||publish_date = 13 April 2026
|description = Coronal mass ejections can begin their trajectory highly tilted to the vertical, but then straighten out
|image=Icon522.png}}

{{Nugget Badge
|title = Can EUV Power-Spectral Indices Reveal Imminent Solar Flares?
|number = 521
|first_author = Sihui ZHONG,
|second_author = Dmitrii KOLOTKOV and Valery M. NAKARIAKOV
||publish_date = 6 April 2026
|description = A new flare-precursor observable - power spectra
|image=Icon521.png}}

{{Nugget Badge
|title = How energetic can solar flares become?
|number = 520
|first_author = Natalie KRIVOVA
||publish_date = 31 March 2026
|description = The history of active-region areas suggests the possibility of solar superflares
|image=Icon520.png}}

{{Nugget Badge
|title = Hinode EIS Observations of Plasma Composition Evolution and Radiative Cooling of Flare Loops
|number = 519
|first_author = Teodora MIHĂILESCU,
|second_author = Peter YOUNG et AL.
||publish_date = 16 March 2026
|description = Higher FIP bias than expected in some flare loops, a diagnostically interesting result
|image=Icon519.png}}

{{Nugget Badge
|title = When Magnetic Field Lines Stretch, Snap, and Expand: A New Look at Solar Flares with L-maps
|number = 518
|first_author = Maria KAZACHENKO,
|second_author = Yuhong FAN and Andrey AFANASYEV
||publish_date = 9 March 2026
|description = A clever new tool tracks magnetic connectivity (and energy) during flare/CME occurrence
|image=Icon518.png}}

{{Nugget Badge
|title = Observational Evidence Linking Loop Length and Thermal/Nonthermal Peak Timing in Solar Flares
|number = 517
|first_author = Solomon PERRIYIL
||publish_date = 23 February 2026
|description = Clear evidence for the universality of the physics behind the Neupert Effect
|image=Icon517.png}}

{{Nugget Badge
|title = A fine-scale bright kernel captured by Hi-C 3 in the post-maximum phase of an M-class solar flare
|number = 516
|first_author = Sanjiv TIWARI
||publish_date = 9 February 2026
|description = The Hi-C rocket catches an extremely compact brightening in late-phase flare ribbon development
|image=Icon516.png}}

{{Nugget Badge
|title = On the Relationship Between Nanoflare Energy and Delay in the Closed Solar Corona
|number = 515
|first_author = Shanwlee SOW MONDAL et al.
||publish_date = 19 January 2026
|description = Nanoflaring implies energy storage and sudden release, suggesting correlation between event energy and its timing
|image=Icon515.png}}

{{Nugget Badge
|title = Fine structures in solar flare ribbons
|number = 514
|first_author = Jonas THOEN FABER
||publish_date = 12 January 2026
|description = Elongated "riblets" commonly rise out of flare ribbons, and have characteristic Doppler shifts
|image=Icon514.png}}

{{Nugget Badge
|title = The M- and X-class White-light Flares in Super Active Region NOAA 13664/13697
|number = 513
|first_author = Zhichen JING
|second_author = and Ying LI
|publish_date = 5 January 2026
|description = "Super" active regions have relatively more frequent X-class flares, which correlate well with visible continuum (white-light flare) emission
|image=Icon513.png}}

{{Nugget Badge
|title = Iron Fluorescence in X-class Solar Flares
|number = 512
|first_author = Abhilash SARWADE
|publish_date = 8 December 2025
|description = A new spectroscopic capability for Iron K-alpha fluorescence
|image=Icon512.png}}

{{Nugget Badge
|title = Sun-as-a-star Analysis of a Solar Eruption Source Region Using H-alpha Spectroscopic Observations from CHASE
|number = 510
|first_author = Xiaofeng LIU
|second_author = and Yijun HOU
|publish_date = 24 November 2025
|description = Sun-as-a-star observations help to translate solar/stellar processes
|image=Icon5010.png}}

{{Nugget Badge
|title = On the Origin of Solar Long-Duration Gamma-Ray Flares‎‎‎‎
|number = 509
|first_author = Alessandro BRUNO
|publish_date = 3 November 2025
|description = Do we really need a CME to produce a long-duration solar gamma-ray event?
|image=Icon509.png}}

{{Nugget Badge
|title = FAI and GOES eclipses‎‎
|number = 508
|first_author = Hugh HUDSON
|publish_date = 20 October 2025
|description = Flare anticipation via FAI may have problems during GOES eclipses, which are really interesting in their own right
|image=Icon508.png}}

{{Nugget Badge
|title = The EUV Late Phase‎
|number = 507
|first_author = Sascha ORNIG
|publish_date = 13 October 2025
|description = Basic comparative statistics of the ELP, a distinct flare phenomenon
|image=Icon507.png}}

{{Nugget Badge
|title = Time evolution of flare-accelerated electrons using the warm-target model‎
|number = 506
|first_author = Debesh BHATTACHARJEE
|publish_date = 6 October 2025
|description = Considering a "warm" thick target allows flare-accelerated electrons to be treated self-consistently
|image=Icon506.png}}

{{Nugget Badge
|title = SOLSTICE observes flare Doppler shifts in Si III
|number = 505
|first_author = Luke MAJURY
|publish_date = 30 September 2025
|description = A rarely used database suggests prograde-flow Doppler shifts in flaring plasmas
|image=Icon505.png}}

{{Nugget Badge
|title = Flare Phases and the Earth's Ionospheric Response
|number = 504
|first_author = Susanna BEKKER
|publish_date = 16 September 2025
|description = A flare's "EUV late phase" is surprisingly geoeffective
|image=Icon504.png}}

{{Nugget Badge
|title = Neupertianity
|number = 503
|first_author = Hugh HUDSON
|publish_date = 25 August 2025
|description = It's hard to avoid the Neupert Effect
|image=Icon503.png}}

{{Nugget Badge
|title = Synchrotron Radiation and the Foundations for a Cosmic Bridge
|number = 502
|first_author = Immanuel JEBARAJ
|publish_date = 11 August 2025
|description = Gyrosynchrotron radiation in shocks: a cosmic connection
|image=Icon502.png}}

{{Nugget Badge
|title = The Aulanier Effect: drifting footpoints of CME flux ropes
|number = 501
|first_author = Jaroslav DUDÍK,
|second_author = Juraj LÖRINČÍK and Brigitte SCHMIEDER
|publish_date = 21 July 2025
|description = The breakthrough to 3D flare physics: the Aulanier Effect
|image=Icon501.png}}

{{Nugget Badge
|title = Five Hundred Nuggets
|number = 500
|first_author = Hugh HUDSON
|publish_date = 14 July 2025
|description = A milestone
|image=Icon169.png}}

{{Nugget Badge
|title = Quasiperiodic Pulsations in the Balmer Continuum in an X-class Solar White-light Flare
|number = 499
|first_author = De-Chao SONG et al.
|publish_date = 30 June 2025
|description = QPP in the Balmer continuum: the powerful heartbeat of a flare
|image=Icon499.png}}

{{Nugget Badge
|title = High-Resolution Observations of a C3 class White-Light Flare
|number = 498
|first_author = Zhe XU and
|second_author = Xiaoli YAN
|publish_date = 16 June 2025
|description = A compact white-light flare with vortical motions (and hard X-rays)
|image=Icon498.png}}

{{Nugget Badge
|title = The Sun's open-closed flux boundary and the origin of the slow solar wind
|number = 497
|first_author = Chloe WILKINS and
|second_author = David PONTIN
|publish_date = 26 May 2025
|description = Identifying the solar sources of slow solar wind
|image=Icon497.png}}

{{Nugget Badge
|title = Delay of Near-Relativistic Electrons
|number = 496
|first_author = Grant MITCHELL
|publish_date = 19 May 2025
|description = Parker Solar Probe solves an old mystery about type III bursts
|image=Icon496.png}}

{{Nugget Badge
|title = A Multi-Site Telescope for Multi-Height for Synoptic Observations
|number = 495
|first_author = Fallon KONOW
|publish_date = 11 May 2025
|description = A new synoptic network for observations at multiple wavelengths
|image=Icon495.png}}

{{Nugget Badge
|title = On turbulent magnetic reconnection: fast and slow mean steady-states
|number = 494
|first_author = Sage STANISH
|second_author = and David MacTAGGART
|publish_date = 28 April 2025
|description = In a turbulent medium, magnetic reconnection has two limiting domains
|image=Icon494.png}}

{{Nugget Badge
|title = Quasi-Periodic Pulsations in Ionospheric TEC and Flare EUV
|number = 493
|first_author = Aisling O'HARE
|publish_date = 21 April 2025
|description = The Earth's ionosphere reflects QPPs, with a small delay
|image=Icon493.png}}

{{Nugget Badge
|title = Metis observations of Alfvenic outflows driven by interchange reconnection in a pseudostreamer
|number = 492
|first_author = Paolo ROMANO and the Metis team
|publish_date = 7 April 2025
|description = Exactly as predicted by numerical simulations... a rare coup
|image=Icon492.png}}

{{Nugget Badge
|title = Solar Rollercoaster: looping-the-loop in the solar corona
|number = 491
|first_author = Mohamed NEDAL et al.
|publish_date = 31 March 2025
|description = Large-scale helical motion in the flare/CME SOL2024-05-14
|image=Icon491.png}}

{{Nugget Badge
|title = Proton Beam Energy Deposition as a Mechanism of Deep Photospheric Heating
|number = 490
|first_author = Samuel GRANOVSKY
|second_author = and Alexander KOSOVICHEV
|publish_date = 17 March 2025
|description = Evidence for proton beams in white-light flares
|image=Icon490.png}}

{{Nugget Badge
|title = New insights into the proton precipitation sites in solar flares
|number = 489
|first_author = Andrea Francesco BATTAGLIA
|second_author = and Säm KRUCKER
|publish_date = 17 February 2025
|description = There is no detectable difference in proton and electron foopoint locations after all
|image=Icon489.png}}

{{Nugget Badge
|title = Solar Gamma-Ray Evidence for a Distinct Population of MeV Flare-Accelerated Electrons
|number = 488
|first_author = Gerry SHARE
|second_author =
|publish_date = 10 February 2025
|description = Relativistic electrons in solar flares newly recognized as a distinct process
|image=Icon488.png}}

{{Nugget Badge
|title = From Chromospheric Evaporation to Coronal Rain: An Investigation of the Mass and Energy Cycle of a Flare‎
|number = 487
|first_author = Seray &Scedil;AHIN
|second_author = and Patrick ANTOLIN
|publish_date = 3 February 2025
|description = A first quantitative comparison of flare evaporation and coronal rain
|image=Icon487.png}}

{{Nugget Badge
|title = Energetic neutral atoms detected in the large solar energetic particle event of February 2022‎
|number = 486
|first_author = Christina COHEN
|second_author =
|publish_date = 20 January 2025
|description = Only the second direct observation of high-energy neutral atoms from the Sun
|image=Icon486.png}}

{{Nugget Badge
|title = Magnetic topology of quiet-Sun Ellerman bombs and associated ultraviolet brightenings‎
|number = 485
|first_author = Aditi BHATNAGAR
|second_author =
|publish_date = 6 January 2025
|description = Tiny "Ellerman Bombs" occur all across the solar surface, with differences
|image=Icon485.png}}

{{Nugget Badge
|title = Unveiling CME Dynamics: Rare Rotations of CMEs in the Heliosphere
|number = 484
|first_author = Sandeep KUMAR and
|second_author = Nandita SRIVASTAVA
|publish_date = 30 December 2024
|description = CMEs usually do not show additional rotation as they move though the heliosphere
|image=Icon484.png}}

{{Nugget Badge
|title = Spatial and Spectral Evolution of Microwave and X-Ray Sources During the Limb Flare SOL2023-02-05
|number = 483
|first_author = Yulia N. SHAMSUTDINOVA
|publish_date = 23 December 2024
|description = Rare microwave imaging spectroscopy of a hot-onset precursor event
|image=Icon483.png}}

{{Nugget Badge
|title = High-resolution observational analysis of flare ribbon fine structures
|number = 482
|first_author = Jonas THOEN FABER
|publish_date = 16 December 2024
|description = Spatially periodic fine structures in flare ribbons reveal current-sheet tearing
|image=Icon482.png}}

{{Nugget Badge
|title = Advection and super-diffusive expansion as the model of flare accelerated electron transport in type III solar radio bursts
|number = 481
|first_author = Eduard KONTAR
|publish_date = 9 December 2024
|description = Sturrock's dilemma resolved
|image=Icon481.png}}

{{Nugget Badge
|title = Faraday's Law in Solar Flares: A Cautionary Message
|number = 480
|first_author = Michael FARADAY
|publish_date = 2 December 2024
|description = We must not forget the global implications of Faraday's Law
|image=Icon480.png}}

{{Nugget Badge
|title = Remarkable NUV Spectrum of an M-star Megaflare
|number = 479
|first_author = Adam KOWALSKI
|publish_date = 25 November 2024
|description = Remarkable NUV spectra from an HST stellar flare
|image=Icon479.png}}

{{Nugget Badge
|title = Revised Point-Spread Functions of AIA and their effect on DEM analyses
|number = 478
|first_author =Stefan HOFMEISTER,
|second_author = Daniel Wolf SAVIN, and Michael HAHN
|publish_date = 18 November 2024
|description = Substantial revisions of the AIA point-response functions
|image=Icon478.png}}

{{Nugget Badge
|title = How much of the energy in flare-accelerated electrons reaches the chromosphere?
|number = 477
|first_author = Meriem ALAOUI
|second_author = and Gordon HOLMAN
|publish_date = 11 November 2024
|description = Keeping flare-accelerated electrons out of the chromosphere
|image=Icon477.png}}

{{Nugget Badge
|title = Spatially resolved plasma composition evolution in a solar flare
|number = 476
|first_author = Andy S. H. TO
|publish_date = 4 November 2024
|description = Reconnection outflow feeds abundance variations
|image=Icon476.png}}

{{Nugget Badge
|title = HOPE during high activity
|number = 475
|first_author = Hugh HUDSON
|second_author = and Alphonse STERLING
|publish_date = 28 October 2024
|description = Hot onsets appear even in the most active solar conditions
|image=Icon475.png}}

{{Nugget Badge
|title = Simulated heliospheric electron spectra show sensitivity to plasma properties of a source region in the flaring corona
|number = 474
|first_author = Ross PALLISTER
|second_author = and Natasha JEFFREY
|publish_date = 21 October 2024
|description = Getting closer to an understanding of how solar energetic particles "escape"
|image=Icon474.png}}

{{Nugget Badge
|title = An extremely complex active region with very strong non-neutralized electric currents
|number = 473
|first_author = Ioannis KONTOGIANNIS
|publish_date = 14 October 2024
|description = Large non-neutralized electric currents flow through the active-region corona
|image=Icon473.png}}

{{Nugget Badge
|title = An X9 flare and its huge crochet (SFE)
|number = 472
|first_author = Hugh HUDSON
|publish_date = 7 October 2024
|description = The geomagnetic effect (SFE/crochet) that will calibrate the Carrington flare
|image=Icon472.png}}

{{Nugget Badge
|title = All microflares that accelerate electrons to high energies are rooted in sunspots
|number = 471
|first_author = Andrea Francesco BATTAGLIA
|publish_date = 30 September 2024
|description = Microflares with hard X-ray spectra are a well-defined class, and invariably have one footpoint embedded in a sunspot
|image=Icon471.png}}

{{Nugget Badge
|title = The warm-target model and kappa distributions
|number = 470
|first_author = Yingjie LUO
|publish_date = 16 September 2024
|description = A self-consistent treatment of non-thermal electron spectra points to kappa distributions
|image=Icon470.png}}

{{Nugget Badge
|title = Is there HOPE for Hyder flares...
|number = 468
|first_author = Hugh HUDSON
|publish_date = 15 March 2024
|description = Filament eruptions/Hyder flares/disparitions brusques may all show HOPE
|image=Icon468.png}}

{{Nugget Badge
|title = Sun-as-a-star Analysis of the M8.7 Flare on 2022 October 2 Using H-alpha and EUV Spectra Taken by SMART/SDDI and SDO/EVE
|number = 467
|first_author = Takato OTSU
|publish_date = 19 February 2024
|description = Whole-Sun spectroscopic observations can readily detect ejecta
|image=Icon467.png}}

{{Nugget Badge
|title = Unexpected Asymmetry in GeV Emission
|number = 466
|first_author = Bruno ARSIOLI and Elena ORLANDO
|publish_date = 15 January 2024
|description = The high-energy solar gamma radiation shows inexplicable but fascinating properties
|image=Icon466.png}}

{{Nugget Badge
|title = When it rippled in one place and exploded in another
|number = 465
|first_author = Ivan ZIMOVETS
|publish_date = 25 December 2023
|description = Pulsations precede a flare, but seem unrelated
|image=Icon465.png}}

{{Nugget Badge
|title = Solar flares: evaporation and simulation‎
|number = 464
|first_author = Malcolm DRUETT
|publish_date = 18 December 2023
|description = Fitting beam electrons into multi-dimensional models
|image=Icon464.png}}

{{Nugget Badge
|title = Pre-impulsive and Impulsive Phases of the March 28, 2022 Sub-Terahertz Flare
|number = 463
|first_author = Galina G. MOTORINA
|publish_date = 11 December 2023
|description = A flare with an increasing sub-THz spectrum and sub-THZ precursor information
|image=Icon463.png}}

{{Nugget Badge
|title = Coronal Bright Points
|number = 462
|first_author = Daniel NÓBREGA-SIVERIO
|publish_date = 27 November 2023
|description = Bright EUV rowel-like structures can result from null-point reconnection
|image=Icon462.png}}

{{Nugget Badge
|title = Aurora-like Radio Emission from a Sunspot
|number = 461
|first_author = Sijie YU
|publish_date = 20 November 2023
|description = Maser action above a sunspot
|image=Icon461.png}}

{{Nugget Badge
|title = Search for a Flare Anticipation Index (FAI)
|number = 460
|first_author = Hugh HUDSON
|second_author = and Jim McTiernan
|publish_date = 13 November 2023
|description = Quantifying flare precursors on a few-minute time scale
|image=Icon460.png}}

{{Nugget Badge
|title = Bouncing motions of fast electrons using Nobeyama Radioheliograph
|number = 459
|first_author = Keitarou MATSUMOTO
|publish_date = 6 November 2023
|description = Solar evidence for conservation of second adiabatic invariant in particle motion
|image=Icon459.png}}

{{Nugget Badge
|title = Impact of nanoflare heating in the lower solar atmosphere
|number = 458
|first_author = Helle BAKKE
|publish_date = 30 October 2023
|description = The behavior of nanoflare fast electrons in Bifrost models
|image=Icon458.png}}

{{Nugget Badge
|title = Precise timing of flare footpoint sources from mid-infrared observations‎
|number = 457
|first_author = Paulo SIMÕES et al.
|publish_date = 23 October 2023
|description = Mid-IR observations at high spatial and high temporal resolution: Conjugacy
|image=Icon457.png}}

{{Nugget Badge
|title = The Greatest GOES Flares‎
|number = 456
|first_author = Hugh HUDSON
|second_author = and Ed CLIVER
|publish_date = 25 September 2023
|description = The greatest GOES events, re-analyzed, fall short of expectations
|image=Icon456.png}}

{{Nugget Badge
|title = Introducing SunSketcher
|number = 455
|first_author = Hugh HUDSON
|second_author = and Gordon EMSLIE
|publish_date = 11 September 2023
|description = Galloping towards roundup in the 2024 total solar eclipse
|image=Icon455.png}}

{{Nugget Badge
|title = TeV Gamma rays from the Quiescent Sun
|number = 454
|first_author = Mehr Un NISA
|second_author = and John BEACOM
|publish_date = 21 August 2023
|description = Solar photons at unprecedented high energies
|image=Icon454.png}}

{{Nugget Badge
|title = Temporal and Spatial Characteristics of Hard X-Ray Sources in Flare Model with Vertical Current Sheet
|number = 453
|first_author = Alexander SHABALIN, Eugenia OVCHINNIKOVA,
|second_author = and Yuri CHARIKOV
|publish_date = 7 August 2023
|description = Modeling betatron acceleration in current-sheet development.
|image=Icon453.png}}

{{Nugget Badge
|title = Spatial Distribution of Magnetic Reconnection Rate in an M6.5 Solar Flare
|number = 452
|first_author = Ju JING
|publish_date = 12 June 2023
|description = Linking hard X-rays to high-resolution images that show reconnection rates.
|image=Icon452.png}}

{{Nugget Badge
|title = Statistical study of Type III bursts and associated HXR emissions
|number = 451
|first_author = Nicole VILMER and Tomin JAMES
|publish_date = 29 May 2023
|description = Linking electron populations escaping from the Sun with those that RHESSI detects.
|image=Icon451.png}}

{{Nugget Badge
|title = Solar flare hard X-rays from the anchor points of an eruptive filament
|number = 450
|first_author = Muriel STIEFEL
|publish_date = 15 May 2023
|description = A rare "four-ribbon" flare has been detected in hard X-rays.
|image=Icon450.png}}

{{Nugget Badge
|title = Did a Solar Flare Accelerate all the Ambient Electrons in the Coronal Acceleration Region?...
|number = 449
|first_author = Gordon EMSLIE, Eduard KONTAR,
|second_author = Galina MOTORINA, and Brian DENNIS
|publish_date = 1 May 2023
|description = Considering SOL2017-09-10, probably not.
|image=Icon449.png}}

{{Nugget Badge
|title = Diagnostics of Spatially-Extended Turbulent Acceleration and Transport
|number = 448
|first_author = Morgan STORES
|publish_date = 24 April 2023
|description = Drilling down into the detailed structure of solar-flare energy release by including turbulence with particle acceleration.
|image=Icon448.png}}

{{Nugget Badge
|title = RHESSI's Re-entry
|number = 447
|first_author = Pascal SAINT-HILAIRE and
|second_author = Hugh HUDSON
|publish_date = 17 April 2023
|description = The final demise of RHESSI is this week
|image=Icon447.png}}

{{Nugget Badge
|title = A Glasgow geomagnetic observation of a solar flare
|number = 446
|first_author = Hugh HUDSON, John MALONE-LEIGH,
|second_author = Graham WOAN, and Chris OSBORNE
|publish_date = 13 March 2023
|description = Irish and Scottish geomagnetic observatories see a crochet much like that of the Carrington event
|image=Icon_446.png}}

{{{Nugget Badge
|title = Particle Acceleration in Two Coronal Jets
|number = 445
|first_author = Yixian ZHANG
|publish_date = 27 February 2023
|description = Coronal jets with hard X-ray sources at disjoint locations
|image=Icon445.png}}

{{Nugget Badge
|title = The Curious First Sunquake of Solar Cycle 25‎
|number = 444
|first_author = Alexander KOSOVICHEV
|publish_date = 13 February 2023
|description = A double whammy: two distinct sunquakes from SOL2022-05-10.
|image=Icon444.png}}

{{Nugget Badge
|title = Hard X-ray Pulsations via Gaussian Decomposition
|number = 443
|first_author = Hannah COLLIER and Laura HAYES
|publish_date = 30 January 2023
|description = Flare hard X-ray time variations decomposed objectively
|image=Icon443.png}}

{{Nugget Badge
|title = A possible coronal magnetic flare precursor
|number = 442
|first_author = Enrico LANDI
|publish_date = 16 January 2023
|description = Novel measurements of the coronal magnetic field may help with flare prediction
|image=Icon442.png}}

{{Nugget Badge
|title = A slow HOPE with microwave context
|number = 441
|first_author = Hugh HUDSON
|publish_date = 12 December 2022
|description = A new microwave facility at Chashan Observatory, and a prototypical HOPE
|image=Icon441.png}}

{{Nugget Badge
|title = Rapid variations of Si IV spectra in a flare observed by IRIS at a sub-second cadence
|number = 440
|first_author = Juraj LÖRINČÍK
|publish_date = 14 November 2022
|description = Transition-region lines in a flare have a Doppler component revealing quasi-periodic pulsations
|image=Icon440.png}}

{{Nugget Badge
|title = A Significant Sudden Ionospheric Disturbance Associated with a Massive Gamma-ray Burst
|number = 439
|first_author = Laura HAYES and Peter GALLAGHER
|publish_date = 31 October 2022
|description = A first SID observed in broad daylight, from a source far far away
|image=Icon439.png}}

{{Nugget Badge
|title = Effects of Coronal Structures on the Dynamics of the Global Coronal Wave of SOL2017-09-10‎
|number = 438
|first_author = Huidong HU, Ying D. LIU, and Bei ZHU
|publish_date = 17 October 2022
|description = The amazing global coronal wave of SOL2017-09-10 wrapped around the whole Sun, and displayed transmission and reflection at both polar coronal holes
|image=Icon438.png}}

{{Nugget Badge
|title = KW-Sun: The Konus-Wind Solar Flare Database in Hard X-Ray and Soft Gamma-Ray Ranges
|number = 437
|first_author = Alexandra LYSENKO
|publish_date = 26 September 2022
|description = An unrivaled hard X-ray and gamma-ray database is entering its third activity maximum
|image=Icon437.png}}

{{Nugget Badge
|title = First Detection of Kink Oscillations with Solar Orbiter
|number = 436
|first_author = Sihui ZHONG et al.
|publish_date = 19 September 2022
|description = SolO sees coronal oscillations as well as AIA can, and even better
|image=Icon436.png}}

{{Nugget Badge
|title = Energetic Neutral Hydrogen from Large Solar Flares
|number = 435
|first_author = Glenn MASON
|publish_date = 6 September 2022
|description = A rediscovered data treasury reveals the occurrence of many flare/CME events producing solar high-energy neutral atoms
|image=Icon435.png}}

{{Nugget Badge
|title = Fifty-year Anniversary of the First Detection of Gamma rays from a Solar Flare
|number = 434
|first_author = Jim Ryan,
|second_author = Brian Dennis, and Phil Dunphy
|publish_date = 8 August 2022
|description = The rich astrophysics of gamma-ray astronomy began with solar observations fifty years ago
|image=Icon434.png}}

{{Nugget Badge
|title = Fast Prograde Flows in Solar Active Regions
|number = 433
|first_author = Hugh HUDSON
|publish_date = 25 July 2022
|description = Unexpected, unpredicted, and not modeled yet - weird flows in hot active-region loops
|image=Icon433.png}}

{{Nugget Badge
|title = Undetected Minority-polarity Flux, Moss, and Coronal Heating
|number = 432
|first_author = Yi-Ming WANG
|publish_date = 11 July 2022
|description = There's plenty of room in "unipolar" active regions for both polarities, and there is good evidence for them
|image=Icon432.png}}

{{Nugget Badge
|title = Thermal/Nonthermal with MinXSS and RHESSI
|number = 431
|first_author = Shunsaku NAGASAWA
|publish_date = 13 June 2022
|description = Time-domain studies of improved X-ray spectra reveal a "super-hot' component
|image=Icon431.png}}

{{Nugget Badge
|title = Sun-as-a-star spectroscopic observations of the line-of-sight velocity of a solar eruption on October 28, 2021
|number = 430
|first_author = Yu XU
|second_author = and Hui TIAN
|publish_date = 30 May 2022
|description = The observation of the full 3d velocity of a CME, for an anniversary event
|image=Icon430.png}}

{{Nugget Badge
|title = Carl Størmer
|number = 429
|first_author = Hugh HUDSON
|second_author = and Lyndsay FLETCHER
|publish_date = 15 April 2022
|description = Størmer and the theory of trapping in loops
|image=Icon429.png}}

{{Nugget Badge
|title = Solar Hard X-rays with Insight
|number = 428
|first_author = Wei WANG
|second_author = and Ping ZHANG
|publish_date = 21 March 2022
|description = A spectacular limb flare introduces Insight/HXMT, a new observational resource
|image=Icon428.png}}

{{Nugget Badge
|title = Probing chromospheric current sheets using SST and ALMA co-observations
|number = 427
|first_author = João da SILVA SANTOS
|publish_date = 21 February 2022
|description = Emerging magnetic flux appears in ALMA images reflecting coronal current sheets
|image=Icon427.png}}

{{Nugget Badge
|title = A demonstration of STIX hard X-ray imaging spectroscopy capabilities for an X-class flare (SOL2021-10-28)
|number = 426
|first_author = Andrea BATTAGLIA, Hannah COLLIER,
|second_author = and Säm KRUCKER
|publish_date = 7 February 2022
|description = STIX imaging of an X-class flare marks its success
|image=Icon426.png}}

{{Nugget Badge
|title = A solar flare driven by thermal conduction observed in mid-infrared
|number = 425
|first_author = Guillermo GIMÉNEZ de CASTRO
|publish_date = 24 January 2022
|description = Strong 10-micron emission from a GOES C2 flare suggests conductive heating
|image=Icon425.png}}

{{Nugget Badge
|title = Disk Occultation of a Lopsided Sun‎
|number = 424
|first_author = Hugh HUDSON,
|second_author = Stephen WHITE and Säm KRUCKER
|publish_date = 10 January 2022
|description = Observing a spotless Sun can enable observations of the faint corona.
|image=Icon424.png}}

{{Nugget Badge
|title = Resolving two distinct thermal X-ray components in a compound solar flare
|number = 423
|first_author = Zhenjun ZHOU
|second_author = and Rui LIU
|publish_date = 28 December 2021
|description = Superhot coronal sources may be independent loop systems
|image=Icon423.png}}

{{Nugget Badge
|title = Bridging solar flares to coronal mass ejections
|number = 422
|first_author = Markus ASCHWANDEN
|publish_date = 14 December 2021
|description = The Neupert effect allows us to trace coronal mass ejections seamlessly
|image=Icon422.png}}

{{Nugget Badge
|title = The Jakimiec Diagnostic Diagram
|number = 421
|first_author = Hugh HUDSON
|publish_date = 29 November 2021
|description = The joint variation of GOES temperature and emission measure discloses new features via an old tool
|image=Icon421.png}}

{{Nugget Badge
|title = First look at ALMA/HInode/IRIS microflares
|number = 420
|first_author = Toshifumi SHIMIZU
|second_author = et al.
|publish_date = 8 November 2021
|description = High-resolution ALMA and multiwavelength observations of microflaring
|image=Icon420.png}}

{{Nugget Badge
|title = Thomson scattering near sunspots
|number = 419
|first_author = Pascal Saint-Hilaire
|second_author = et al.
|publish_date = 25 October 2021
|description = Completing the modeling of low-coronal Thomson polarimetry
|image=Icon419.png}}

{{Nugget Badge
|title = A Non-PFSS Global Coronal Model
|number = 418
|first_author = Oliver RICE
|second_author = and Anthony YEATES
|publish_date = 11 October 2021
|description = Modeling as convenient as PFSS but much more realistic
|image=Icon418.png}}

{{Nugget Badge
|title = Manifold Nonthermality
|number = 417
|first_author = Marina BATTAGLIA
|second_author = et al.
|publish_date = 27 September 2021
|description = Even weak flares involve multiple sites of non thermal activity
|image=Icon417.png}}

{{Nugget Badge
|title = X-Rays from a Type I Radio Burst
|number = 416
|first_author = R. RAMESH
|publish_date = 20 September 2021
|description = A first identification of type I radio emission with hot plasma
|image=Icon416.png}}

{{Nugget Badge
|title = Do Hot Onsets Predict Flare Magnitudes?
|number = 415
|first_author = Hugh HUDSON
|publish_date = 30 August 2021
|description = Maybe we can tell how big a flare is going to be from its initial development...
|image=Icon415.png}}

{{Nugget Badge
|title = Confined or Eruptive?
|number = 414
|first_author = Ting LI et al.
|publish_date = 16 August 2021
|description = Increased magnetic flux reduces CME eruptivity
|image=Icon414.png}}

{{Nugget Badge
|title = Impulsive and Gradual Eruptive Gamma Flares and Associated CMEs
|number = 413
|first_author = Alexey STRUMINSKY,
|second_author = Irina GRIGORIEVA and Andrei SADOVSKI
|publish_date = 19 July 2021
|description = Extreme behavior of flare/CME events explained by environment
|image=Icon373.png}}

{{Nugget Badge
|title = The Morphology of Flare Time Profiles
|number = 412
|first_author = Larisa KASHAPOVA
|second_author = et al.
|publish_date = 12 July 2021
|description = Systematic comparison of solar and stellar flaring time profiles
|image=Icon412.png}}

{{Nugget Badge
|title = Flare Pulsation and the Heliosphere
|number = 411
|first_author = Brendan CLARKE
|second_author = et al.
|publish_date = 5 July 2021
|description = Flare pulsations link closely to the distant heliosphere
|image=Icon411.png}}

{{Nugget Badge
|title = STIX, the Hard X-Ray Telescope on board Solar Orbiter
|number = 410
|first_author = Andrea Francesco BATTAGLIA
|second_author = and Säm KRUCKER
|publish_date = 28 June 2021
|description = STIX is operational and producing great data
|image=Icon410.png}}

{{Nugget Badge
|title = Nonequilibrium Ionization of Flare Plasma Observed by Hinode/EIS
|number = 409
|first_author = Shinsuke IMADA
|second_author =
|publish_date = 14 June 2021
|description = Evidence for non-equilibrium ionization in the current sheet of SOL2017-09-10
|image=Icon409.png}}

{{Nugget Badge
|title = Effects of Flares on Solar p-modes
|number = 408
|first_author = Maria-Cristina RABELLO SOARES
|second_author = and Frederic BAUDIN
|publish_date = 26 April 2021
|description = No detectable p-mode amplitude changes due to solar flares
|image=Icon408.png}}

{{Nugget Badge
|title = Subsecond Spikes in Solar Flare X-ray Flux as Seen by Fermi GBM
|number = 407
|first_author =Trevor KNUTH
|second_author = and Lindsay GLESENER
|publish_date = 19 April 2021
|description = A new analysis technique pushes hard X-ray time scales to 0.1 sec or faster
|image=Icon407.png}}

{{Nugget Badge
|title = Negative He 10830 Flare Ribbons and Non-thermal Electrons
|number = 406
|first_author = Graham KERR
|second_author =
|publish_date = 12 April 2021
|description = A 1D radiation hydrodynamics model can explain the dark leading edges of He I flare ribbons
|image=Icon406.png}}

{{Nugget Badge
|title = Tracing the sources of gradual solar energetic particle events
|number = 405
|first_author = David H. BROOKS
|second_author = and Stephanie L. YARDLEY
|publish_date = 29 March 2021
|description = Chemical abundances in SEPs suggest an origin in flare-related moss regions
|image=Icon405.png}}

{{Nugget Badge
|title = The Superflare SOL2017-09-06: from submm to mid-IR
|number = 404
|first_author = Guillermo (Guigue) GIMÉNEZ DE CASTRO
|second_author =
|publish_date = 15 March 2021
|description = Glimpsing the "missing decades" of the flare emission spectrum
|image=Icon404.png}}

{{Nugget Badge
|title = The Neupert Effect Revisited
|number = 403
|first_author = Jiong QIU
|second_author =
|publish_date = 8 March 2021
|description = Two time scales for heating individual flare strands
|image=Icon403.png}}

{{Nugget Badge
|title = FLUKA as a tool for interpreting flare gamma-rays
|number = 402
|first_author = Alec MACKINNON
|second_author =
|publish_date = 1 March 2021
|description = The nuclear physics of solar flares captured in a detailed model
|image=Icon402.png}}

{{Nugget Badge
|title = A Collective Study of 11 NuSTAR Microflares
|number = 401
|first_author = Jessie DUNCAN and
|second_author = Lindsay GLESENER
|publish_date = 22 February 2021
|description = Swarms of NuSTAR micro flares
|image=Icon401.png}}

{{{{Nugget Badge
|title = A Solar FRB
|number = 400
|first_author = Dale GARY and
|second_author = Hugh HUDSON
|publish_date = 15 February 2021
|description = A new frontier in the solar time domain
|image=Icon400.png}}

{{Nugget Badge
|title = Richard Schwartz
|number = 399
|first_author = Brian DENNIS and
|second_author = Hugh HUDSON
|publish_date = 25 January 2021
|description = Remembering a friend and colleague
|image=Icon399.jpg}}

{{Nugget Badge
|title = Observing Solar Flare X-ray Polarization with Prospective CubeSat Missions
|number = 398
|first_author = Natasha JEFFREY
|publish_date = 4 January 2021
|description = The polarization of the solar X-ray spectrum generally remains to be observed
|image=Icon398.png}}

{{Nugget Badge
|title = Solar effects in the local interstellar medium
|number = 397
|first_author = Don GURNETT and
|second_author = Hugh HUDSON
|publish_date = 14 December 2020
|description = Relativistic particle events observed _in situ_ in the interstellar medium
|image=Icon397.png}}

{{Nugget Badge
|title = Investigation of Small-Scale Energy Releases in Hard X-rays with FOXSI
|number = 396
|first_author = Subramania ATHIRAY and
|second_author = Juliana VIEVERING
|publish_date = 7 December 2020
|description = Hard X-rays and high temperatures from the feeblest microflares
|image=Icon396.png}}

{{Nugget Badge
|title = What drives impulsive coronal heating?
|number = 395
|first_author = Pradeep CHITTA
|second_author = et al.
|publish_date = 30 November 2020
|description = Impulsive footpoint emissions suggest magnetic reconnection in the chromosphere
|image=Icon395.png}}

{{Nugget Badge
|title = Probing the solar coronal heating function with slow magnetoacoustic waves
|number = 394
|first_author = Dmitrii KOLOTKOV
|second_author = et al.
|publish_date = 16 November 2020
|description = Coronal heating models meet damped slow magnetoacoustic waves
|image=Icon394.png}}

{{Nugget Badge
|title = Self-Consistent Flare Model
|number = 393
|first_author = Wenzhi RUAN
|second_author = and Rony KEPPENS
|publish_date = 2 November 2020
|description = Energy transport by fast particles made self-consistent with MHD flare modeling
|image=Icon393.png}}

{{Nugget Badge
|title = Hot Flare Onsets
|number = 392
|first_author = Hugh HUDSON
|second_author = et al.
|publish_date = 26 October 2020
|description = The initial soft X-ray temperatures of solar flares tend to be in the 10-15 MK range
|image=Icon392.png}}

{{Nugget Badge
|title = Electric Current Neutralization and Eruption
|number = 391
|first_author = Ellis AVALLONE
|second_author = and Xudong SUN
|publish_date = 19 October 2020
|description = Coronal currents without neutralizing return currents appear to
|image=Icon391.png}}

{{Nugget Badge
|title = Prediction of Solar Cycle 25
|number = 390
|first_author = Leif SVALGAARD
|second_author =
|publish_date = 5 October 2020
|description = Now we know how big the next solar maximum will be
|image=Icon390.png}}

{{Nugget Badge
|title = Flare/CME Cartoon Archive
|number = 389
|first_author = Hugh HUDSON
|second_author =
|publish_date = 27 September 2020
|description = A new edition of the Flare/CME archive, nearly a half kilotoon now
|image=Icon389.png}}

{{Nugget Badge
|title = Submerged Flare Acoustic Sources
|number = 388
|first_author = Juan Camilo BUITRAGO CASAS
|second_author = and Angel MARTÍNEZ
|publish_date = 13 September 2020
|description = Flare acoustic radiation emanates from a source _inside_ the Sun
|image=Icon388.png}}

{{Nugget Badge
|title = Circular Ribbon Flare at Microwaves
|number = 387
|first_author = Jeongwoo LEE
|second_author =
|publish_date = 31 August 2020
|description = Breakout reconnection reveals itself via microwave polarization measurements.
|image=Icon387.png}}

{{Nugget Badge
|title = Relation of Non-neutralized electric currents and the activity in active regions
|number = 386
|first_author = P. VEMAREDDY
|second_author =
|publish_date = 24 August 2020
|description = Non-neutralized coronal current systems contribute to CME eruptions
|image=Icon386.png}}

{{Nugget Badge
|title = White-light emission and photospheric magnetic field changes in flares
|number = 385
|first_author = J. Sebastián CASTELLANOS DURÁN
|second_author = and Lucia KLEINT
|publish_date = 17 August 2020
|description = There are strong correlations between white-light flare emissions and line-of-sight magnetic field changes
|image=Icon385.png}}

{{Nugget Badge
|title = Sunspot Differential Rotation in an X-class Flare
|number = 384
|first_author = Richard GRIMES,
|second_author = Balázs PINTÉR and Huw MORGAN
|publish_date = 10 August 2020
|description = Observations suggesting how the coronal tail can wag the photospheric dog
|image=Icon384.png}}

{{Nugget Badge
|title = Energy Partitioning in a Nonthermally Dominated Two-loop Solar Flare
|number = 383
|first_author = Galina MOTORINA
|second_author = et al.
|publish_date = 3 August 2020
|description = Modeling the propagation of energy via GX Simulator in an early-impulsive flare
|image=Icon383.png}}

{{Nugget Badge
|title = SOL2013-11-10 Eruptive Circular-ribbon Flare with Extended Remote Brightenings
|number = 382
|first_author = Chang LIU
|second_author = et al.
|publish_date = 31 July 2020
|description = A circular-ribbon event can launch an eruption by breaking through its separatrix dome
|image=Icon382.png}}

{{Nugget Badge
|title = Extreme-Ultraviolet Late Phase of Solar Flares
|number = 381
|first_author = Rui LIU
|second_author =
|publish_date = 22 June 2020
|description = Both arcade and circular-ribbon flares may sometimes spawn EUV late phase emission
|image=Icon381.png}}

{{Nugget Badge
|title = Energy transport by accelerated particles in the quiet solar atmosphere
|number = 380
|first_author = Lars FROGNER,
|second_author = Boris GUDIKSEN and Helle BAKKE
|publish_date = 15 June 2020
|description = A first study of non-thermal particles integrated into an MHD simulation of the solar atmosphere
|image=Icon380.png}}

{{Nugget Badge
|title = Quasi-periodic pulsations as indicators of oscillatory processes in solar flares
|number = 379
|first_author = Elena KUPRIYANOVA
|second_author = et al.
|publish_date = 11 May 2020
|description = Many, many QPPs
|image=Icon379.png}}

{{Nugget Badge
|title = Rejuvenating Solar Flare Termination Shocks as Particle Accelerators
|number = 378
|first_author = Bin CHEN
|second_author =
|publish_date = 4 May 2020
|description = At last, clear evidence for a long-predicted phenomenon
|image=Icon378.png}}

{{Nugget Badge
|title = Broad symmetrical Doppler-shifted Fe XXI line profiles
|number = 377
|first_author = Vanessa POLITO
|second_author =
|publish_date = 20 April 2020
|description = It is difficult to explain "evaporation" line profiles by superposition of unresolved flows
|image=Icon377.png}}

{{Nugget Badge
|title = Phenomena in the unusually long pre-impulsive phase of SOL2011-06-07
|number = 376
|first_author = Marian KARLICKÝ,
|second_author = Jana KA&Scaron;PAROVÁ, and Robert SYCH
|publish_date = 13 April 2020
|description = A massive and slowly-rising filament eruption reveals important new signatures of the physics
|image=Icon376.png}}

{{Nugget Badge
|title = Evidence for a Coronal Shock Wave Origin for Relativistic Protons Producing Solar Gamma-Rays and Observed by Neutron Monitors at Earth‎
|number = 375
|first_author = Athanasios KOULOUMVAKOS
|second_author = and Gerry SHARE
|publish_date = 6 April 2020
|description = Successful modeling of prolonged solar gamma-ray emissions and terrestrial ground-level cosmic-ray events
|image=Icon375.png}}

{{Nugget Badge
|title = Using overlappogram data to find hot flare plasma
|number = 374
|first_author = Louise HARRA
|
|publish_date = 23 March 2020
|description = Imaging Fe XXIV at high resolution with the EIS slot data
|image=Icon374.png}}

{{Nugget Badge
|title = SOL2017-09-04 (M5.5) 2017 as a Source of Relativistic Electrons and Protons
|number = 373
|first_author = Alexei STRUMINSKII
| (see text)
|publish_date = 16 March 2020
|description = Flare-accelerated particles, rather than SEPs, energize sustained gamma-ray emission
|image=Icon373.png}}

{{Nugget Badge
|title = Heating of the solar photosphere during a white-light flare‎
|number = 372
|first_author = Jan JURČÁK
| (see text)
|publish_date = 2 March 2020
|description = The best-ever spectrum of the flare photosphere
|image=Icon372.png}}

{{Nugget Badge
|title = A Hot Cusp-Shaped Confined Solar Flare
|number = 371
|first_author = Aaron HERNANDEZ-PEREZ
|publish_date = 24 February 2020
|description = A flare may have a prominent hot cusp with the help of any eruption
|image=Icon371.png}}

{{Nugget Badge
|title = The Temporal and Spatial Extension of Gamma-ray Emission from the Sun
|number = 370
|first_author = Nat GOPALSWAMY
|publish_date = 17 February 2020
|description = Sustained solar γ-rays and solar cosmic rays
|image=Icon370.ng.png}}

{{Nugget Badge
|title = A PSP Perihelion
|number = 369
|first_author = Jessie DUNCAN
|second_author = and Hugh Hudson
|publish_date = 20 January 2020
|description = The Parker Solar Probe enters its fourth perihelion already. Now
|image=Icon369.png}}

{{Nugget Badge
|title = Remembering John Brown
|number = 368
|first_author = Alec MacKINNON
|second_author =
|publish_date = 13 January 2020
|description = John passed away unexpectedly on 16 November 2019
|image=Icon368.png}}

{{Nugget Badge
|title = A Global Survey of EUV Coronal Power Spectra
|number = 367
|first_author = Karl Battams
|second_author =
|publish_date = 30 December 2019
|description = Time-series parameter maps of imaged power spectra from an AIA pipeline
|image=Icon367.png}}

{{Nugget Badge
|title = Cosmic Rays over the Rainbow Bridge
|number = 366
|first_author = Hugh Hudson
|second_author = Alec MacKinnon
|publish_date = 16 December 2019
|description = Cosmic rays approach the Sun
|image=Icon366.png}}

{{Nugget Badge
|title = Spectropolarimetric Insight into Plasma-Sheet Dynamics of a Solar Flare
|number = 365
|first_author = Ryan French
|second_author =
|publish_date = 9 December 2019
|description = CoMP polarization patterns in SOL2017-09-10 are amazing
|image=Icon365.png}}

{{Nugget Badge
|title = Lorentz Force Evolution Reveals the Energy Build-up Processes during Recurrent Eruptive Solar Flares‎
|number = 364
|first_author = Ranadeep Sarkar,
|second_author = Nandita Srivastava and Astrid Veronig
|publish_date = 18 November 2019
|description = The net Lorentz force clearly exhibits a build-up and release pattern
|image=Icon364.png}}

{{Nugget Badge
|title = Flare waiting times depend on their magnitudes
|number = 363
|first_author = Hugh Hudson
|second_author =
|publish_date = 11 November 2019
|description = Surprising new evidence for the flare build-up and release process
|image=Icon363.png}}

{{Nugget Badge
|title = Can magnetic reconnection cause solar rainstorms?‎
|number = 362
|first_author = Petra Kohutova
|second_author =
|publish_date = 4 November 2019
|description = Impulsive coronal heating resulting from reconnection can trigger coronal rain
|image=Icon362.png}}

{{Nugget Badge
|title = Non-radial jets on the edges of active regions
|number = 361
|first_author = Peter Wyper
|second_author =
|publish_date = 14 October 2019
|description = The very common jet structures we see can naturally combine twist and breakout
|image=Icon361.png}}

{{Nugget Badge
|title = Searching SOLfully within the Nuggets
|number = 360
|first_author = Hugh Hudson
|second_author =
|publish_date = 7 October 2019
|description = The IAU target identifier works well for finding items about a particular event
|image=Icon360.png}}

{{Nugget Badge
|title = Submillimeter Radiation as the Thermal Component of the Neupert Effect
|number = 359
|first_author = Guillermo Giménez de Castro
|second_author =
|publish_date = 31 September 2019
|description = Flare radiation at the highest frequencies can be bremsstrahlung
|image=Icon359.png}}

{{Nugget Badge
|title = The "Last Best" Flares
|number = 358
|first_author = Hugh Hudson,
|second_author = Ed Cliver, and Brian Dennis
|publish_date = 24 September 2019
|description = Major flares tend to happen at the very ends of sunspot cycles
|image=Icon358.png}}

{{Nugget Badge
|title = Dynamic Processes of the Moreton Wave on 2014 March 29‎
|number = 357
|first_author = Denis Cabezas
|second_author = and the FMT team
|publish_date = 16 September 2019
|description = A beautiful Moreton wave excited by the best-observed flare ever
|image=Icon357.png}}

{{Nugget Badge
|title = EVE-RHESSI DEM Models and the Low-energy Cutoff for Nonthermal Electrons
|number = 356
|first_author = Jim McTiernan
|second_author =
|publish_date = 9 September 2019
|description = Characterizing flare temperature distributions helps to define the non-thermal energy release
|image=Icon356.png}}

{{Nugget Badge
|title = Stealth Coronal Mass Ejections from Active Regions
|number = 355
|first_author = Jennifer O'Kane
|second_author =
|publish_date = 26 August 2019
|description = Perhaps just feeble versions of the same magnetic disease...
|image=Icon355.png}}

{{Nugget Badge
|title = Do Kepler Superflare Stars Really Include Slowly Rotating Sun-like Stars?‎
|number = 354
|first_author = Yuta NOTSU
|second_author =
|publish_date = 15 July 2019
|description = Kepler superflares hint at solar superflares
|image=Icon354.png}}

{{Nugget Badge
|title = Localized Microwave and EUV Bright Structures in an Eruptive Prominence
|number = 353
|first_author = Jing HUANG
|second_author =
|publish_date = 22 June 2019
|description = Detailed correlations between EUV and microwaves in prominence fine structures
|image=Icon353.png}}

{{Nugget Badge
|title = Broken-up hard X-ray spectra found for a loop-top source during a solar limb flare
|number = 352
|first_author = Hao NING,
|second_author = Yao CHEN and Jeongwoo LEE
|publish_date = 16 June 2019
|description = SOL2017-09-10 coronal hard X-ray sources
|image=Icon352.png}}

{{Nugget Badge
|title = The Cosmic-Ray Shadow and Coronal Magnetism
|number = 351
|first_author = Frederik Tenholt
|second_author =
|publish_date = 27 May 2019
|description = The coronal magnetic field measured in Antarctica
|image=Icon351.png}}

{{Nugget Badge
|title = Kristian Birkeland
|number = 350
|first_author = Hugh HUDSON
|second_author = and Lyndsay FLETCHER
|publish_date = 6 May 2019
|description = Space weather a century ago: Kristian Birkeland
|image=Icon350.png}}

{{Nugget Badge
|title = Warm UV loops heated by small-scale cancellation events
|number = 349
|first_author = Seray ŞAHIN
|second_author = and Vasyl YURCHYSHYN
|publish_date = 22 April 2019
|description = Precisely locating the footpoints of warm coronal loops helps identify their source(s) of excitation
|image=Icon349.png}}

{{Nugget Badge
|title = Multiple Regions of Shock-accelerated Particles during a Solar Coronal Mass Ejection
|number = 348
|first_author = Diana MOROSAN
|second_author =
|publish_date = 1 April 2019
|description = LOFAR identifies herringbone sources within the flank of the SOL2017-09-10 shock - no joke
|image=Icon348.png}}

{{Nugget Badge
|title = Persistent Quasi-Periodic Pulsations Detected During the Large X8.2 Solar Flare
|number = 347
|first_author = Laura HAYES
|second_author = and Peter GALLAGHER
|publish_date = 25 March 2019
|description = The most beautiful flare has the most beautiful pulsations
|image=Icon347.png}}

{{Nugget Badge
|title = Is the coronal magnetic field braiding?
|number = 346
|first_author = Markus ASCHWANDEN
|second_author =
|publish_date = 11 March 2019
|description = This iconic cartoon does not relate well to the observations
|image=Icon346.png}}

{{Nugget Badge
|title = An energetic pre-flare: electron distributions in magnetic reconnection outflows
|number = 345
|first_author = Marina BATTAGLIA,
|second_author = Eduard KONTAR and Galina MOTORINA
|publish_date = 18 February 2019
|description = Assessing energy partition in a pre-impulsive flare development
|image=Icon345.png}}

{{Nugget Badge
|title = Linear Polarization in H-alpha Flares
|number = 344
|first_author = Tomoko KAWATE
|second_author = and Yoichiro HANAOKA
|publish_date = 4 February 2019
|description = H-alpha polarization is rarely observable but, in once case, very suggestive
|image=Icon344.png}}

{{Nugget Badge
|title = Short-Period Waves
|number = 343
|first_author = Sijie YU
|second_author = and Bin CHEN
|publish_date = 21 January 2019
|description = New decimetric imaging spectroscopy suggests Alfvénic energy transport in flares
|image=Icon343.png}}

{{Nugget Badge
|title = The Interesting RHESSI/SAS Archive
|number = 342
|first_author = Hugh HUDSON
|second_author = and Martin FIVIAN
|publish_date = 8 January 2019
|description = The full mission database shows RHESSI to have been very stable geometrically
|image=Icon342.png}}

{{Nugget Badge
|title = Homologous White Light Solar Flares‎
|number = 341
|first_author = Paolo ROMANO
|second_author = and Abouazza ELMHAMDI
|publish_date = 31 December 2018
|description = Homologous white-light flares, in rapid succession, and coronal null points
|image=Icon341.png}}

{{Nugget Badge
|title = The flight of FOXSI-3
|number = 340
|first_author = Lindsay GLESENER
|second_author = and Noriyuki NARUKAGE
|publish_date = 10 December 2018
|description = Single-photon counting and direct focusing across hard and soft energies
|image=Icon340.png}}

{{Nugget Badge
|title = Stellar Flares and Starspots
|number = 339
|first_author = Lauren DOYLE
|second_author =
|publish_date = 3 December 2018
|description = Stellar flares don't spatially match their starspots
|image=Icon339.png}}

{{Nugget Badge
|title = Neutron Production in Solar Flares
|number = 338
|first_author = Ron MURPHY
|second_author = and Gerry SHARE
|publish_date = 26 November 2018
|description = Neutron astronomy helps us understand solar flares
|image=Icon338.png}}

{{Nugget Badge
|title = Cycle 25 Strikes Again
|number = 337
|first_author = Kamil BICZ
|second_author =
|publish_date = 20 November 2018
|description = A second, larger Cycle 25 sunspot
|image=Icon337.png}}

{{Nugget Badge
|title = Remembering Marcos Machado via his research
|number = 336
|first_author = Hugh HUDSON
|second_author =
|publish_date = 13 November 2018
|description = Recalling a friend and colleague, and admiring his final paper
|image=Icon336.png}}

{{Nugget Badge
|title = CORONAS/SPIRIT Mg XII and Nanoflares‎
|number = 335
|first_author = Anton REVA
|second_author =
|publish_date = 22 October 2018
|description = Monochromatic Mg XII spectroheliography sets severe limits on nanoflare heating models
|image=Icon335.png}}

{{Nugget Badge
|title = White-light Emission and Non-thermal Electrons‎
|number = 334
|first_author = Kyoung-Sun LEE
|second_author =
|publish_date = 8 October 2018
|description = An intimate relationship between accelerated electrons and visible flare continuum
|image=Icon334.png}}

{{Nugget Badge
|title = Coronal Hard X-ray Sources Revisited
|number = 333
|first_author = Brian DENNIS
|second_author =
|publish_date = 24 September 2018
|description = Reporting some over-interpretation of the evidence for "coronal thick targets"
|image=Icon333.png}}

{{Nugget Badge
|title = Photospheric response to a flare
|number = 332
|first_author = Mike WHEATLAND
|second_author =
|publish_date = 17 September 2018
|description = Sudden changes in the magnetic field in the low atmosphere associated with particle acceleration
|image=Icon332.png}}

{{Nugget Badge
|title = New Views of Global Solar Magnetic Field Evolution Over Four Solar Cycles
|number = 331
|first_author = David WEBB
|second_author =
|publish_date = 27 August 2018
|description = A digital archive of Pat McIntosh's 44 years of solar synoptic observations
|image=Icon331.png}}

{{Nugget Badge
|title = Understanding the co-spatial return current in solar flares
|number = 330
|first_author = Meriem ALAOUI
|second_author = and Gordon HOLMAN
|publish_date = 6 August 2018
|description = Completing the circuit in a thick-target model
|image=Icon330.png}}

{{Nugget Badge
|title = 3D Magnetic Reconnection at a Coronal Null Point
|number = 329
|first_author = Shane MALONEY,
|second_author = Aidan O'Flannagain and Peter Gallagher
|publish_date = 30 July 2018
|description = Large-scale reconnection involved in Type I radio noise storm
|image=Icon329.png}}

{{Nugget Badge
|title = The true dawn of multimessenger astronomy
|number = 328
|first_author = Hugh Hudson
|second_author =
|publish_date = 23 July 2018
|description = Ever since the Carrington flare
|image=Icon328.png}}

{{Nugget Badge
|title = Microwave Imaging Spectroscopy of Flares is Here‎
|number = 327
|first_author = Dale E. Gary,
|second_author = EOVSA and RHESSI Teams
|publish_date = 16 July 2018
|description = Microwave imaging spectroscopy takes a giant leap forward with SOL2017-09-10
|image=Icon327.png}}

{{Nugget Badge
|title = Coronal nanoflares powered by footpoint reconnection
|number = 326
|first_author = Pradeep Chitta,
|second_author = Hardi Peter, and Sami Solanki
|publish_date = 9 July 2018
|description = Coronal nanoflares in active region cores can be powered by the magnetic reconnection in the lower solar atmosphere
|image=Icon326.png}}

{{Nugget Badge
|title = A remarkable, but confused, coronal hard X-ray source
|number = 325
|first_author = Alexandra Lysenko,
|second_author = Larisa Kashapova and Hugh Hudson
|publish_date = 25 June 2018
|description = A remarkable flare in 1999 adds to our short list of extended coronal hard X-ray/microwave sources
|image=Icon325.png}}

{{Nugget Badge
|title = Understanding HMI pseudocontinuum in white-light flares‎
|number = 324
|first_author = Michal &Scaron;vanda
|second_author = et al.
|publish_date = 28 May 2018
|description = The HMI pseudocontinuum (Ic) is ill-calibrated in regions with strong fields, i.e. for white-light flares
|image=Icon324.png}}

{{Nugget Badge
|title = To beam or not to beam - that is (still) the question
|number = 323
|first_author = Paulo Simões
|second_author = and Hugh Hudson
|publish_date = 14 May 2018
|description = Descriptions of the lower solar atmosphere of flares ca. Cycle 21 sound surprisingly current
|image=Icon323.png}}

{{Nugget Badge
|title = Observation of Cosmic Ray Spallation Events from SoHO‎
|number = 322
|first_author = Serge Koutchmy
|second_author = and Ehsan Tavabi
|publish_date = 7 May 2018
|description = LASCO's images capture high-energy nuclear interactions from cosmic-ray hits
|image=Icon322.png}}

{{Nugget Badge
|title = A Sunspot from Cycle 25 for sure
|number = 321
|first_author = Tomek Mrozek
|second_author = and Hugh Hudson
|publish_date = 10 April 2018
|description = YES! Cycle 25 is here!
|image=Icon321.png}}

{{Nugget Badge
|title = Blue-wing enhancement of the Mg II h and k lines in a flare
|number = 320
|first_author = Akiko TEI
|second_author =
|publish_date = 9 April 2018
|description = Flare loops involve a cool upflow preceding the hot evaporation flow
|image=Icon320.png}}

{{Nugget Badge
|title = NuSTAR detects X-ray flares in the quiet Sun
|number = 319
|first_author = Matej Kuhar
|second_author = and Säm Krucker
|publish_date = 26 March 2018
|description = Quiet-Sun flares may not be powerful, but they look a lot like ordinary flares
|image=Icon319.png}}

{{Nugget Badge
|title = Homologous CME/flares from AR 12371
|number = 318
|first_author = Panditi Vemareddy
|second_author = and Pascal Demoulín
|publish_date = 19 March 2018
|description = An excellent set of homologous flare/CMEs analyzed and explained
|image=Icon318.png}}

{{Nugget Badge
|title = Non-Maxwellian Diagnostics from SDO/EVE Spectra of an X-class Flare
|number = 317
|first_author = Elena Dzifčáková
|second_author = and Jaroslav Dudík
|publish_date = 16 February 2018
|description = Ratios of high-excitation ions can readily detect κ-distributions in flare plasmas
|image=Icon317.png}}

{{Nugget Badge
|title = Joint MinXSS and RHESSI Flare X-ray Spectra between 1 and 15 keV
|number = 316
|first_author = Chris Moore, Brian Dennis and the MinXSS Science Team
|publish_date = 5 February 2018
|description = MinXSS adds systematic views of flare soft X-ray spectra to RHESSI imagery
|image=Icon316.png}}

{{Nugget Badge
|title = Parameterized Flare Models with Chromospheric Compressions
|number = 315
|first_author = Adam Kowalski & Joel Allred
|publish_date = 17 January 2018
|description = A new approach to modeling the lower flare atmosphere
|image=FlareModelsKowalskiAllred.png}}

{{Nugget Badge
|title = A Curious Sunspot Group in 2018
|number = 314
|first_author = Hugh Hudson
|publish_date = 14 January 2018
|description = The first new sunspot group of 2018 emerged at the wrong latitude
|image = Icon314.png}}

{{Nugget Badge
|title = Tecumseh's Eclipse and Astrophysics
|number = 313
|first_author = Hugh Hudson
|publish_date = 25 December 2017
|description = The solar corona was first recognized as such, and named, in an eclipse of 1806
|image = Icon313.png}}

{{Nugget Badge
|title = Hunting for Hidden Tiny Flares
|number = 312
|first_author = Shin-nosuke ISHIKAWA
|publish_date = 27 November 2017
|description = FOXSI-2 says that episodic energy releases are still viable as a part of the coronal heating problem.
|image = Icon312.png}}

{{Nugget Badge
|title = Unusual Type III Burst Dynamics Produced by Diverging Magnetic Fields
|number = 311
|first_author = Patrick McCauley
|publish_date = 20 November 2017
|description = Unusual type III bursts follow coronal separatrix structures.
|image = Icon311.png}}

{{Nugget Badge
|title = Valderrama in the 21st Century
|number = 310
|first_author = Hugh Hudson
|publish_date = 31 October 2017
|description = A newly-described white-light flare from the 19th century!..
|image = Icon310.png}}

{{Nugget Badge
|title = Electron Scattering in the Flaring Corona
|number = 309
|first_author = Sophie Musset
|publish_date = 24 October 2017
|description = Diffusive transport may contribute to the trapping of electrons in coronal X-ray sources
|image = Icon309.png}}

{{Nugget Badge
|title = The Power of Turbulence
|number = 308
|first_author = Nic Bian
|publish_date = 25 September 2017
|description = Turbulent energy content may underlie flare energy transfer, magnetic reconnection, and particle acceleration
|image = Icon308.png}}

{{Nugget Badge
|title = The Kelvin Force and Loop-Top Concentration
|number = 307
|first_author = Kiyoto SHIBASAKI
|publish_date = 18 September 2017
|description = New physics can explain the perplexing overpressure at the flare looptop regions
|image = Icon307.png}}

{{Nugget Badge
|title = The Last Best Flare of Cycle 24?
|number = 306
|first_author = Säm Krucker
|second_author = and Hugh Hudson
|publish_date = 11 September 2017
|description = Right on schedule, Cycle 24 has produced a great flare (with a GLE)
|image = Icon306.png}}

{{Nugget Badge
|title = Electric Current Neutralization and Solar Eruption in Active Regions
|number = 305
|first_author = Yang LIU
|second_author =
|publish_date = 28 August 2017
|description = Active current systems in the solar corona don't have return currents
|image = Icon305.png}}

{{Nugget Badge
|title = RHESSI and the Megamovie
|number = 304
|first_author = Hugh Hudson, Laura Peticolas,
|second_author = and Juan Carlos Martínez Oliveros
|publish_date = 31 July 2017
|description = A wholly new way to view a solar eclipse, and to do solar astrometry
|image = Icon304.png}}

{{Nugget Badge
|title = Bastille Day 2017
|number = 303
|first_author = Hugh Hudson
|second_author = and Säm Krucker
|publish_date = 24 July 2017
|description = Interesting flares really do happen on Bastille Day...
|image = Icon303.png}}

{{Nugget Badge
|title = The Solar X-ray Limb III
|number = 302
|first_author = Marina Battaglia
|second_author = and Gordon Hurford
|publish_date = 12 June 2017
|description = RHESSI succeeds with a wholly new way to measure the solar diameter
|image = Icon302.png}}

{{Nugget Badge
|title = Double Coronal X-ray and Microwave Sources Associated With A Magnetic Breakout Solar Eruption
|number = 301
|first_author = Yao CHEN
|second_author =
|publish_date = 29 May 2017
|description = A different explanation of the double coronal hard X-ray sources
|image = Icon301.png}}

{{Nugget Badge
|title = A Lasso Model for Solar Gamma-ray Events
|number = 300
|first_author = Hugh Hudson
|second_author =
|publish_date = 15 May 2017
|description = A toy model hoping to explain the SEP/LAT relationship
|image = Icon300.png}}

[[RHESSI Science Nuggets 200 to 299|Next Nuggets]]

How Extreme Can Solar Flares Get? A Statistical View

2026-05-05T13:21:24Z

Hhudson:

{{Infobox Nugget |name = Nugget
|title = How Extreme Can Solar Flares Get? A Statistical View
|number = 525
|first_author = Lapo CECCARELLI
|second_author = Daniela CASTRO-CAMILO
|publish_date = May 4, 2026
|next_nugget = TBD
|previous_nugget = {{#ask: [[Category:Nugget]] [[RHESSI Nugget Index::524]]}}
}}

== Introduction ==

Quantifying the upper limits of solar flare activity is central to
understanding
[https://heliowiki.smce.nasa.gov/wiki/index.php/Extreme_events,_stellar_evolution,_and_magnetic_reconnection space weather]
risk. In this work, we analyse the lengthy
record of soft X-ray (1-8 Å) fluxes from
[https://www.swpc.noaa.gov/products/goes-x-ray-flux GOES]
(1975-2022, see Figure 1 and Ref. [1]) through the lens of Extreme
Value Theory ([https://en.wikipedia.org/wiki/Extreme_value_theory EVT]),
focusing explicitly on the statistical structure
of the tail of the flare-intensity distribution function.

[[File:525f1.png|center|thumb|600px|caption|Figure 1: 
Time series of the peak flux for each solar flare event from 1975 to 2022,
W/m2 for the 1-8 Å band.
]]

== Extreme Value Modelling Framework ==

We adopt two complementary EVT approaches. First, a block maxima
framework, modeling weekly maxima using the Generalised Extreme Value
(GEV) distribution.
Second, a peaks-over-threshold (POT) approach, modeling the
exceedances above a high quantile (a specified threshold) using the
Generalised Pareto Distribution (GPD).
These approaches target the same tail behaviour but rely on different
asymptotic regimes, providing a useful consistency check.

The GPD distribution for exceedances y = X - u > 0 is defined as

[[File:525eq1.png|thumb|center|500px]]

where μ is the real-valued "location parameter", σ > 0 is the
"scale parameter", and ξ is the "shape parameter" governing the
behaviour of the tail of the distribution, i.e. the greatest values.

The GPD distribution for exceedances y = X - u > 0 is defined as:

[[File:525eq2.png|thumb|center|600px]]

where σu > 0 is the scale parameter above threshold u
and ξ is the same shape parameter controlling tail "heaviness".

A key quantity in both formulations is the shape parameter, which
governs tail heaviness. Our estimates consistently suggest a positive
shape parameter, indicating heavy-tailed behaviour and supporting
the plausibility of very large events beyond the observed range.

== Diagnostics and Model Assessment ==

We assess model adequacy using standard EVT diagnostics.
"Quantile-quantile" plots (Figure 2) show good agreement between empirical
and fitted distributions in the tail region.
"Dependence diagnostics" further highlight the role of temporal
clustering, suggesting that extreme flares may not occur independently,
an aspect that is partially accounted for through the weekly
aggregation in the GEV framework.

[[File:525f2.png|center|thumb|600px|caption|Figure 2: 
Quantile plot for the selected GEV model, where the location and
scale parameters are a smooth function of the background level and
week of the event.
]]

== Return Levels and Risk Quantification ==

[https://en.wikipedia.org/wiki/Return_period "Return level"] estimates
derived from both GEV and GPD models (Figure 3 shows results for
the GEV model) provide a quantitative interpretation of extreme
flare magnitudes. Extrapolation indicates that
[https://heliowiki.smce.nasa.gov/wiki/index.php/The_1859_Space_Weather_Event_Revisited Carrington]-like
events correspond to return periods on the order of a century, while
more extreme scenarios remain within the support of the fitted
heavy-tailed models. Importantly, uncertainty increases rapidly
with the return period, as reflected in widening confidence intervals.
This highlights the intrinsic difficulty of inference in the far
tail, even with several decades of satellite data.

[[File:525f3.png|center|thumb|600px|caption|Figure 3: 
Return Level plot for the selected GEV model. The horizontal dashed
line corresponds to the estimated magnitude of the
[https://heliowiki.smce.nasa.gov/wiki/index.php/The_1859_Space_Weather_Event_Revisited Carrington event],
while the vertical ones represent the 95% confidence interval for
its return period.
]]

== Implications for Solar Physics ==

From a statistical perspective, the results reinforce that assumptions
about the nature of the tail
are critical when extrapolating beyond observed data.
The consistency we find between GEV and GPD approaches strengthens confidence
in the inferred tail behaviour, while also emphasising the limits
of data-driven extrapolation.

== Limitations and Future Directions ==

While the GEV and GPD models provide principled and asymptotically
justified frameworks for modelling extremes, their adequacy is limited
in settings where events are irregularly spaced and potentially
dependent, as is the case for solar flares.
[https://en.wikipedia.org/wiki/Point_process "Point-process"] approaches,
such as the Hawkes self-exciting processes, offer a natural way to
capture temporal clustering and triggering mechanisms. Combining
such models with EVT for the flare magnitudes represents a promising
direction for more realistic and physically informed modelling of
extreme solar activity

== References ==

[1] [https://ui.adsabs.harvard.edu/abs/2024SoPh..299...39H "The Greatest GOES Soft X-ray Flares"]

File:525eq2.png

2026-05-05T13:18:15Z

Hhudson: Hhudson uploaded a new version of File:525eq2.png

File:525eq1.png

2026-05-05T13:17:45Z

Hhudson: Hhudson uploaded a new version of File:525eq1.png