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A New Route to Coronal Vector Magnetometry

2026-09-04T14:05:03Z

Hhudson: author's fixes

{{Infobox Nugget |name = Nugget
|title = Trading Stokes V for Wave Speeds: A New Route to Vector Coronal
Magnetometry
|number = 534
|first_author = Alin PARASCHIV
|publish_date = September 1, 2026
|next_nugget =
|previous_nugget = {{#ask: [[Category:Nugget]] [[RHESSI Nugget Index::532]]}}
}}

== Introduction ==

The magnetic field of the solar corona remains observationally elusive.
At the same time, it is absolutely the most fundamental property defining all
coronal activity.
One of the best approaches to characterizing the field is exploitation of the magnetic sensitivity of the
[https://en.wikipedia.org/wiki/Forbidden_mechanism forbidden]
Fe XIII coronal emission lines in the near infrared (wavelengths around 1 μ).
For a long time, the rule in coronal magnetism seemed simple: if
you wanted the full three-dimensional magnetic field in the corona
you needed the complete polarization signal, in two different
spectral lines.
Coronal light generally carries a polarization fingerprint
that encodes information about the magnetic field, described with
four so-called
[https://en.wikipedia.org/wiki/Stokes_parameters Stokes parameters],
I, Q, U, and V.
The V parameter is the circular polarization, which can be very strong
at radio wavelengths but which can be weak in the visible/IR range.

== Getting at the Stokes parameters ==

The I parameter is just the total intensity;
the linear polarization (Q, U) come from from
the saturated [https://en.wikipedia.org/wiki/Hanle_effect Hanle effect].
This is measurable with current coronal
instruments but is sensitive to the field orientation only.
The circular polarization from the weak-field
[https://nationalmaglab.org/magnet-academy/history-of-electricity-magnetism/museum/zeeman-effect-1896/ Zeeman effect] (Stokes V)
is significantly harder to measure, while being critically needed for
measuring the field strength.
Measurements demand large apertures and
excellent SNR.
Only the [https://en.wikipedia.org/wiki/Daniel_K._Inouye_Solar_Telescope DKIST]
[https://nso.edu/telescopes/dkist/instruments/cryo-nirsp/ Cryo-NIRSP] instrument
has thoroughly delivered on such
measurements so far (Ref. [1]); meanwhile, wide-FOV, small-
aperture instruments like
[https://www2.hao.ucar.edu/mlso/instruments/upgraded-coronal-multi-channel-polarimeter CoMP/UCoMP]
can't realistically chase Stokes V, even
though they are the instruments capable of producing large-
scale, high-cadence maps of the plane-of-the-sky projection
of B, via Alfvénic wave tracking (Ref. [2]).
This, in other words, provides an imaging method for determining BPOS, the
plane-of-the sky field intensity.
Figure 1 illustrates the
[https://www2.hao.ucar.edu/mlso/instruments/upgraded-coronal-multi-channel-polarimeter CoMP]
view of the global corona, showing its full image capability.

[[File:534f1.png|center|thumb|700px|caption|Figure 1: 
A snapshot view of
[https://www2.hao.ucar.edu/mlso/instruments/upgraded-coronal-multi-channel-polarimeter CoMP]
coronal magnetic observations: full coronal images in I, Q, and U, but not so good in V.
]]

== A solution ==

Our study (Ref. [3]) asks whether this Doppler seismology-derived
BPOS can be included in an inverse reconstruction, rather
than being treated as a separate, independent diagnostic. The result
is a new "IQUD" inversion mode where Fe XIII 1074.7/1079.8 nm
IUQ observations are further constrained by a wave-derived B_POS
(the "D" for Doppler-oscillation diagnostic).
The propagating-kink- wave dispersion relation is used in a POS-projected form,
that doesn't
force the field to lie exactly in the plane of sky.
Ref. [3] statistically investigates test cases, showing that IQUD
indistinguishably matches ground truth (IQUV).
This is aside from orientation degeneracies;
IQUD alone returns a 4-fold-degenerate B.
Under perturbation,
matches stay above 96% up to reasonable and observationally achievable
relative-uncertainty levels.
Inversions still exceeded 77% even at a
fairly adverse uncertainties. In other words, performance is limited
by the usual suspects: LOS integration and the single-point-approximation
that are the bane of remote-sensing the optically thin and highly structured
solar corona.
Figure 2 illustrates the four-fold degeneracy issue for the IQUD inversions,
bearing in mind the two-fold degeneracy of IQUV.

[[File:534f3.png|center|thumb|700px|caption|Figure 2: 
Example of degeneracies in IQUV and IQUD inversions. One 4-times
degenerate magnetic solution is represented, where the blue and red
arrows show degeneracies with respect to the x- and z-planes. Three
representative viewports are selected: (A) A plane-of-sky observer projection,
analogous to a ground-based observation. (B) The same projection
but with the equatorial plane rotated by 90 degrees. (C) Polar north looking
down projection perpendicular to the plane of the sky.
]]

== Conclusion ==

Our alternative IQUD approach holds great promise for improvements in global coronal magnetometry, and we are grateful for the Hawaiian observatories on Mauna
Kea (DKIST) and Mauna Loa (UCoMP) that make this possible.

== References ==

[1] [https://ui.adsabs.harvard.edu/abs/2024SciA...10.1604S "Mapping the Sun's coronal magnetic field using the Zeeman effect"]

[2] [http://adsabs.harvard.edu/abs/2007Sci...317.1192T "Alfvén Waves in the Solar Corona"]

[3] [https://arxiv.org/abs/2607.12846 "Inferring 3D Coronal Magnetic Fields Through Seismology-Assisted Inversions of IQU-only Spectropolarimetric Observations"]

SolarNuggets

2026-09-04T08:35:22Z

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 = A New Route to Coronal Vector Magnetometry
|number = 534
|first_author = Alin PARASCHIV
|publish_date = 1 September 2026
|description = An "IQUD" approach to the global vector magnetic field in the corona
|image=Icon534.png}}

{{Nugget Badge
|title = The Variance of Solar X-ray Flux
|number = 533
|first_author = Hugh HUDSON
|publish_date = 17 August 2026
|description = Taylor's law describes solar X-ray variability all the way
|image=Icon533.png}}

{{Nugget Badge
|title = Electron-Ion equilibration in CME-driven shocks
|number = 532
|first_author = John RAYMOND
|publish_date = 3 August 2026
|description = Signatures of heliospheric plasmas not in thermal equilibrium
|image=Icon532.png}}

{{Nugget Badge
|title = The Source Surface Height Through the Solar Cycle: A Path to Better Solar Wind Forecasts
|number = 531
|first_author = Sandeep KUMAR
|second_author = and Nandita SRIVASTAVA
||publish_date = 20 July 2026
|description = Following the solar cycle with optimized PFSS modeling
|image=Icon531.png}}

{{Nugget Badge
|title = Filament Eruptions as seen in the Sun-as-a-star H-alpha Spectrum
|number = 530
|first_author = Junyi ZHANG
|second_author = and Yijun HOU
||publish_date = 6 July 2026
|description = H-alpha from a space platform shows Sun-as-a-star signatures of ejecta
|image=Icon530.png}}

{{Nugget Badge
|title = Particle Pressure and CMEs
|number = 529
|first_author = Hugh HUDSON
|second_author = and Ed CLIVER
||publish_date = 22 June 2026
|description = High-energy particles can exert substantial pressure and affect eruption dynamics
|image=Icon529.png}}

{{Nugget Badge
|title = White-Light and Lyman-alpha Emissions in Solar Flares: Timing, Timescale, Energy, and Scaling‎‎
|number = 528
|first_author = Dechao SONG
||publish_date = 8 June 2026
|description = A new catalog of white-light flares including novel Lyman-alpha data
|image=Icon528.png}}

{{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]]

SolarNuggets

2026-09-04T08:34:20Z

Hhudson: Added No. 534

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 = A New Route to Vector Coronal Magnetometry
|number = 534
|first_author = Alin PARASCHIV
|publish_date = 1 September 2026
|description = An "IQUD" approach to the global vector magnetic field in the corona
|image=Icon534.png}}

{{Nugget Badge
|title = The Variance of Solar X-ray Flux
|number = 533
|first_author = Hugh HUDSON
|publish_date = 17 August 2026
|description = Taylor's law describes solar X-ray variability all the way
|image=Icon533.png}}

{{Nugget Badge
|title = Electron-Ion equilibration in CME-driven shocks
|number = 532
|first_author = John RAYMOND
|publish_date = 3 August 2026
|description = Signatures of heliospheric plasmas not in thermal equilibrium
|image=Icon532.png}}

{{Nugget Badge
|title = The Source Surface Height Through the Solar Cycle: A Path to Better Solar Wind Forecasts
|number = 531
|first_author = Sandeep KUMAR
|second_author = and Nandita SRIVASTAVA
||publish_date = 20 July 2026
|description = Following the solar cycle with optimized PFSS modeling
|image=Icon531.png}}

{{Nugget Badge
|title = Filament Eruptions as seen in the Sun-as-a-star H-alpha Spectrum
|number = 530
|first_author = Junyi ZHANG
|second_author = and Yijun HOU
||publish_date = 6 July 2026
|description = H-alpha from a space platform shows Sun-as-a-star signatures of ejecta
|image=Icon530.png}}

{{Nugget Badge
|title = Particle Pressure and CMEs
|number = 529
|first_author = Hugh HUDSON
|second_author = and Ed CLIVER
||publish_date = 22 June 2026
|description = High-energy particles can exert substantial pressure and affect eruption dynamics
|image=Icon529.png}}

{{Nugget Badge
|title = White-Light and Lyman-alpha Emissions in Solar Flares: Timing, Timescale, Energy, and Scaling‎‎
|number = 528
|first_author = Dechao SONG
||publish_date = 8 June 2026
|description = A new catalog of white-light flares including novel Lyman-alpha data
|image=Icon528.png}}

{{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:Icon534.png

2026-09-04T08:30:43Z

Hhudson:

A New Route to Coronal Vector Magnetometry

2026-09-04T08:27:37Z

Hhudson: /* Conclusion */

{{Infobox Nugget |name = Nugget
|title = Trading Stokes V for Wave Speeds: A New Route to Vector Coronal
Magnetometry
|number = 534
|first_author = Alin PARASCHIV
|publish_date = September 1, 2026
|next_nugget =
|previous_nugget = {{#ask: [[Category:Nugget]] [[RHESSI Nugget Index::532]]}}
}}

== Introduction ==

The magnetic field of the solar corona remains observationally elusive.
At the same time, it is absolutely the most fundamental property defining all
coronal activity.
One of the best approaches to characterizing the field is exploitation of the magnetic sensitivity of the
[https://en.wikipedia.org/wiki/Forbidden_mechanism forbidden]
Fe XIII coronal emission lines in the near infrared (wavelengths around 1 μ).
For a long time, the rule in coronal magnetism seemed simple: if
you wanted the full three-dimensional magnetic field in the corona
you needed the complete polarization signal, in two different
spectral lines.
Coronal light generally carries a polarization fingerprint
that encodes information about the magnetic field, described with
four so-called
[https://en.wikipedia.org/wiki/Stokes_parameters Stokes parameters],
I, Q, U, and V.
The V parameter is the circular polarization, which can be very strong
at radio wavelengths but which can be weak in the visible/IR range.

== Getting at the Stokes parameters ==

The I parameter is just the total intensity;
the linear polarization (Q, U) come from from
the saturated [https://en.wikipedia.org/wiki/Hanle_effect Hanle effect].
This is measurable with current coronal
instruments but is sensitive to the field orientation only.
The circular polarization from the weak-field
[https://nationalmaglab.org/magnet-academy/history-of-electricity-magnetism/museum/zeeman-effect-1896/ Zeeman effect] (Stokes V)
is significantly harder to measure, while being critically needed for
measuring the field strength.
Measurements demand large apertures and
excellent SNR.
Only the [https://en.wikipedia.org/wiki/Daniel_K._Inouye_Solar_Telescope DKIST]
[https://nso.edu/telescopes/dkist/instruments/cryo-nirsp/ Cryo-NIRSP] instrument
has thoroughly delivered on such
measurements so far (Ref. [1]); meanwhile, wide-FOV, small-
aperture instruments like
[https://www2.hao.ucar.edu/mlso/instruments/upgraded-coronal-multi-channel-polarimeter CoMP/UCoMP]
can't realistically chase Stokes V, even
though they are the instruments capable of producing large-
scale, high-cadence maps of the plane-of-the-sky projection
of B, via Alfvénic wave tracking (Ref. [2]).
This, in other words, is an imaging method for determining BPOS, the
plane-of-the sky field intensity.
Figure 1 illustrates the
[https://www2.hao.ucar.edu/mlso/instruments/upgraded-coronal-multi-channel-polarimeter CoMP]
view of the global corona, showing its full image capability.

[[File:534f1.png|center|thumb|700px|caption|Figure 1: 
A snapshot view of
[https://www2.hao.ucar.edu/mlso/instruments/upgraded-coronal-multi-channel-polarimeter CoMP]
coronal magnetic observations: full coronal images in I, Q, and U, but not so good in V.
]]

== A solution ==

Our study (Ref. [3]) asks whether this Doppler seismology-derived
BPOS can be included in an inverse reconstruction, rather
than being treated as a separate, independent diagnostic. The result
is a new "IQUD" inversion mode where Fe XIII 1074.7/1079.8 nm
IUQ observations are further constrained by a wave-derived B_POS
(the "D" for Doppler-oscillation diagnostic).
The propagating-kink- wave dispersion relation is used in a POS-projected form,
that doesn't
force the field to lie exactly in the plane of sky.
Ref. [3] investigates test cases, showing that IQUD matches ground truth (IQUV)
statistically indistinguishable, aside from degeneracy multiplicity
(IQUD alone returns a 4-fold-degenerate B). Under perturbation,
matches stay above 96% up to reasonable and observationally achievable
relative-uncertainty levels. Inversions still exceeded 77% even at a
fairly adverse uncertainties. In other words, performance is limited
by the usual suspects: LOS integration and the single-point-approximation
that are the bane of remote-sensing the optically thin and highly structured
solar corona.
Figure 2 illustrates the four-fold degeneracy issue for the IQUD inversions,
bearing in mind the two-fold degeneracy of IQUV.

[[File:534f3.png|center|thumb|700px|caption|Figure 2: 
Example of degeneracies in IQUV and IQUD inversions. One 4-times
degenerate magnetic solution is represented, where the blue and red
arrows show degeneracies with respect to the x- and z-planes. Three
representative viewports are selected: (A) A plane-of-sky observer projection,
analogous to a ground-based observation. (B) The same projection
but with the equatorial plane rotated by 90 degrees. (C) Polar north looking
down projection perpendicular to the plane of the sky.
]]

== Conclusion ==

Our alternative IQUD approach holds great promise for improvements in global coronal magnetometry, and we are grateful for the Hawaiian observatories on Mauna
Kea (DKIST) and Mauna Loa (UCoMP) that make this possible.

== References ==

[1] [https://ui.adsabs.harvard.edu/abs/2024SciA...10.1604S "Mapping the Sun's coronal magnetic field using the Zeeman effect"]

[2] [http://adsabs.harvard.edu/abs/2007Sci...317.1192T "Alfvén Waves in the Solar Corona"]

[3] [https://arxiv.org/abs/2607.12846 "Inferring 3D Coronal Magnetic Fields Through Seismology-Assisted Inversions of IQU-only Spectropolarimetric Observations"]

A New Route to Coronal Vector Magnetometry

2026-09-04T08:26:32Z

Hhudson: /* Getting at the Stokes parameters */

{{Infobox Nugget |name = Nugget
|title = Trading Stokes V for Wave Speeds: A New Route to Vector Coronal
Magnetometry
|number = 534
|first_author = Alin PARASCHIV
|publish_date = September 1, 2026
|next_nugget =
|previous_nugget = {{#ask: [[Category:Nugget]] [[RHESSI Nugget Index::532]]}}
}}

== Introduction ==

The magnetic field of the solar corona remains observationally elusive.
At the same time, it is absolutely the most fundamental property defining all
coronal activity.
One of the best approaches to characterizing the field is exploitation of the magnetic sensitivity of the
[https://en.wikipedia.org/wiki/Forbidden_mechanism forbidden]
Fe XIII coronal emission lines in the near infrared (wavelengths around 1 μ).
For a long time, the rule in coronal magnetism seemed simple: if
you wanted the full three-dimensional magnetic field in the corona
you needed the complete polarization signal, in two different
spectral lines.
Coronal light generally carries a polarization fingerprint
that encodes information about the magnetic field, described with
four so-called
[https://en.wikipedia.org/wiki/Stokes_parameters Stokes parameters],
I, Q, U, and V.
The V parameter is the circular polarization, which can be very strong
at radio wavelengths but which can be weak in the visible/IR range.

== Getting at the Stokes parameters ==

The I parameter is just the total intensity;
the linear polarization (Q, U) come from from
the saturated [https://en.wikipedia.org/wiki/Hanle_effect Hanle effect].
This is measurable with current coronal
instruments but is sensitive to the field orientation only.
The circular polarization from the weak-field
[https://nationalmaglab.org/magnet-academy/history-of-electricity-magnetism/museum/zeeman-effect-1896/ Zeeman effect] (Stokes V)
is significantly harder to measure, while being critically needed for
measuring the field strength.
Measurements demand large apertures and
excellent SNR.
Only the [https://en.wikipedia.org/wiki/Daniel_K._Inouye_Solar_Telescope DKIST]
[https://nso.edu/telescopes/dkist/instruments/cryo-nirsp/ Cryo-NIRSP] instrument
has thoroughly delivered on such
measurements so far (Ref. [1]); meanwhile, wide-FOV, small-
aperture instruments like
[https://www2.hao.ucar.edu/mlso/instruments/upgraded-coronal-multi-channel-polarimeter CoMP/UCoMP]
can't realistically chase Stokes V, even
though they are the instruments capable of producing large-
scale, high-cadence maps of the plane-of-the-sky projection
of B, via Alfvénic wave tracking (Ref. [2]).
This, in other words, is an imaging method for determining BPOS, the
plane-of-the sky field intensity.
Figure 1 illustrates the
[https://www2.hao.ucar.edu/mlso/instruments/upgraded-coronal-multi-channel-polarimeter CoMP]
view of the global corona, showing its full image capability.

[[File:534f1.png|center|thumb|700px|caption|Figure 1: 
A snapshot view of
[https://www2.hao.ucar.edu/mlso/instruments/upgraded-coronal-multi-channel-polarimeter CoMP]
coronal magnetic observations: full coronal images in I, Q, and U, but not so good in V.
]]

== A solution ==

Our study (Ref. [3]) asks whether this Doppler seismology-derived
BPOS can be included in an inverse reconstruction, rather
than being treated as a separate, independent diagnostic. The result
is a new "IQUD" inversion mode where Fe XIII 1074.7/1079.8 nm
IUQ observations are further constrained by a wave-derived B_POS
(the "D" for Doppler-oscillation diagnostic).
The propagating-kink- wave dispersion relation is used in a POS-projected form,
that doesn't
force the field to lie exactly in the plane of sky.
Ref. [3] investigates test cases, showing that IQUD matches ground truth (IQUV)
statistically indistinguishable, aside from degeneracy multiplicity
(IQUD alone returns a 4-fold-degenerate B). Under perturbation,
matches stay above 96% up to reasonable and observationally achievable
relative-uncertainty levels. Inversions still exceeded 77% even at a
fairly adverse uncertainties. In other words, performance is limited
by the usual suspects: LOS integration and the single-point-approximation
that are the bane of remote-sensing the optically thin and highly structured
solar corona.
Figure 2 illustrates the four-fold degeneracy issue for the IQUD inversions,
bearing in mind the two-fold degeneracy of IQUV.

[[File:534f3.png|center|thumb|700px|caption|Figure 2: 
Example of degeneracies in IQUV and IQUD inversions. One 4-times
degenerate magnetic solution is represented, where the blue and red
arrows show degeneracies with respect to the x- and z-planes. Three
representative viewports are selected: (A) A plane-of-sky observer projection,
analogous to a ground-based observation. (B) The same projection
but with the equatorial plane rotated by 90 degrees. (C) Polar north looking
down projection perpendicular to the plane of the sky.
]]

== Conclusion ==

Our IQUD replacement of IQUV holds great promise for improvements in coronal
magnetometry, and we are grateful for the Hawaiian observatories on Mauna
Kea (DKIST) and Mauna Loa (UCoMP) that make this possible.

== References ==

[1] [https://ui.adsabs.harvard.edu/abs/2024SciA...10.1604S "Mapping the Sun's coronal magnetic field using the Zeeman effect"]

[2] [http://adsabs.harvard.edu/abs/2007Sci...317.1192T "Alfvén Waves in the Solar Corona"]

[3] [https://arxiv.org/abs/2607.12846 "Inferring 3D Coronal Magnetic Fields Through Seismology-Assisted Inversions of IQU-only Spectropolarimetric Observations"]

A New Route to Coronal Vector Magnetometry

2026-09-04T07:49:19Z

Hhudson: /* Introduction */

{{Infobox Nugget |name = Nugget
|title = Trading Stokes V for Wave Speeds: A New Route to Vector Coronal
Magnetometry
|number = 534
|first_author = Alin PARASCHIV
|publish_date = September 1, 2026
|next_nugget =
|previous_nugget = {{#ask: [[Category:Nugget]] [[RHESSI Nugget Index::532]]}}
}}

== Introduction ==

The magnetic field of the solar corona remains observationally elusive.
At the same time, it is absolutely the most fundamental property defining all
coronal activity.
One of the best approaches to characterizing the field is exploitation of the magnetic sensitivity of the
[https://en.wikipedia.org/wiki/Forbidden_mechanism forbidden]
Fe XIII coronal emission lines in the near infrared (wavelengths around 1 μ).
For a long time, the rule in coronal magnetism seemed simple: if
you wanted the full three-dimensional magnetic field in the corona
you needed the complete polarization signal, in two different
spectral lines.
Coronal light generally carries a polarization fingerprint
that encodes information about the magnetic field, described with
four so-called
[https://en.wikipedia.org/wiki/Stokes_parameters Stokes parameters],
I, Q, U, and V.
The V parameter is the circular polarization, which can be very strong
at radio wavelengths but which can be weak in the visible/IR range.

== Getting at the Stokes parameters ==

The I parameter is just the total intensity;
the linear polarization (Q, U) can come from from
the saturated [https://en.wikipedia.org/wiki/Hanle_effect Hanle effect]
is measurable with current coronal
instruments but is sensitive to the field orientation only.
The circular polarization from the weak-field
[https://nationalmaglab.org/magnet-academy/history-of-electricity-magnetism/museum/zeeman-effect-1896/ Zeeman effect] (Stokes V)
is significantly harder to measure, while being critically needed for
measuring the field strength.
Measurements demand large apertures and
excellent SNR.
Only the [https://en.wikipedia.org/wiki/Daniel_K._Inouye_Solar_Telescope DKIST]
[https://nso.edu/telescopes/dkist/instruments/cryo-nirsp/ Cryo-NIRSP] instrument
has thoroughly delivered on such
measurements so far (Ref. [1]); meanwhile, wide-FOV, small-
aperture instruments like
[https://www2.hao.ucar.edu/mlso/instruments/upgraded-coronal-multi-channel-polarimeter CoMP/UCoMP]
can't realistically chase Stokes V, even
though they are the instruments capable of producing large-
scale, high-cadence maps of the plane-of-the-sky projection
of B, via Alfvénic wave tracking (Ref. [2]).
This, in other words, is an imaging method for determining BPOS, the
plane-of-the sky field intensity.
Figure 1 illustrates the
[https://www2.hao.ucar.edu/mlso/instruments/upgraded-coronal-multi-channel-polarimeter CoMP]
view of the global corona, showing its full image capability.

[[File:534f1.png|center|thumb|700px|caption|Figure 1: 
A snapshot view of
[https://www2.hao.ucar.edu/mlso/instruments/upgraded-coronal-multi-channel-polarimeter CoMP]
coronal magnetic observations: full coronal images in I, Q, and U, but not so good in V.
]]

== A solution ==

Our study (Ref. [3]) asks whether this Doppler seismology-derived
BPOS can be included in an inverse reconstruction, rather
than being treated as a separate, independent diagnostic. The result
is a new "IQUD" inversion mode where Fe XIII 1074.7/1079.8 nm
IUQ observations are further constrained by a wave-derived B_POS
(the "D" for Doppler-oscillation diagnostic).
The propagating-kink- wave dispersion relation is used in a POS-projected form,
that doesn't
force the field to lie exactly in the plane of sky.
Ref. [3] investigates test cases, showing that IQUD matches ground truth (IQUV)
statistically indistinguishable, aside from degeneracy multiplicity
(IQUD alone returns a 4-fold-degenerate B). Under perturbation,
matches stay above 96% up to reasonable and observationally achievable
relative-uncertainty levels. Inversions still exceeded 77% even at a
fairly adverse uncertainties. In other words, performance is limited
by the usual suspects: LOS integration and the single-point-approximation
that are the bane of remote-sensing the optically thin and highly structured
solar corona.
Figure 2 illustrates the four-fold degeneracy issue for the IQUD inversions,
bearing in mind the two-fold degeneracy of IQUV.

[[File:534f3.png|center|thumb|700px|caption|Figure 2: 
Example of degeneracies in IQUV and IQUD inversions. One 4-times
degenerate magnetic solution is represented, where the blue and red
arrows show degeneracies with respect to the x- and z-planes. Three
representative viewports are selected: (A) A plane-of-sky observer projection,
analogous to a ground-based observation. (B) The same projection
but with the equatorial plane rotated by 90 degrees. (C) Polar north looking
down projection perpendicular to the plane of the sky.
]]

== Conclusion ==

Our IQUD replacement of IQUV holds great promise for improvements in coronal
magnetometry, and we are grateful for the Hawaiian observatories on Mauna
Kea (DKIST) and Mauna Loa (UCoMP) that make this possible.

== References ==

[1] [https://ui.adsabs.harvard.edu/abs/2024SciA...10.1604S "Mapping the Sun's coronal magnetic field using the Zeeman effect"]

[2] [http://adsabs.harvard.edu/abs/2007Sci...317.1192T "Alfvén Waves in the Solar Corona"]

[3] [https://arxiv.org/abs/2607.12846 "Inferring 3D Coronal Magnetic Fields Through Seismology-Assisted Inversions of IQU-only Spectropolarimetric Observations"]

A New Route to Coronal Vector Magnetometry

2026-09-04T07:47:05Z

Hhudson:

{{Infobox Nugget |name = Nugget
|title = Trading Stokes V for Wave Speeds: A New Route to Vector Coronal
Magnetometry
|number = 534
|first_author = Alin PARASCHIV
|publish_date = September 1, 2026
|next_nugget =
|previous_nugget = {{#ask: [[Category:Nugget]] [[RHESSI Nugget Index::532]]}}
}}

== Introduction ==

The magnetic field of the solar corona remains observationally elusive.
At the same time, it is absolutely the most fundamental property defining all
coronal activity.
One of the best approaches to characterizing the field is exploitation of the magnetic sensitivity of the
[https://en.wikipedia.org/wiki/Forbidden_mechanism forbidden]
Fe XIII coronal emission lines in the near infrared.
For a long time, the rule in coronal magnetism seemed simple: if
you wanted the full three-dimensional magnetic field in the corona
you needed the complete polarization signal, in two different
spectral lines.
Coronal light generally carries a polarization fingerprint
that encodes information about the magnetic field, described with
four so-called
[https://en.wikipedia.org/wiki/Stokes_parameters Stokes parameters],
I, Q, U, and V.
The V parameter is the circular polarization, which can be very strong
at radio wavelengths but which is very weak in the visible band.

== Getting at the Stokes parameters ==

The I parameter is just the total intensity;
the linear polarization (Q, U) can come from from
the saturated [https://en.wikipedia.org/wiki/Hanle_effect Hanle effect]
is measurable with current coronal
instruments but is sensitive to the field orientation only.
The circular polarization from the weak-field
[https://nationalmaglab.org/magnet-academy/history-of-electricity-magnetism/museum/zeeman-effect-1896/ Zeeman effect] (Stokes V)
is significantly harder to measure, while being critically needed for
measuring the field strength.
Measurements demand large apertures and
excellent SNR.
Only the [https://en.wikipedia.org/wiki/Daniel_K._Inouye_Solar_Telescope DKIST]
[https://nso.edu/telescopes/dkist/instruments/cryo-nirsp/ Cryo-NIRSP] instrument
has thoroughly delivered on such
measurements so far (Ref. [1]); meanwhile, wide-FOV, small-
aperture instruments like
[https://www2.hao.ucar.edu/mlso/instruments/upgraded-coronal-multi-channel-polarimeter CoMP/UCoMP]
can't realistically chase Stokes V, even
though they are the instruments capable of producing large-
scale, high-cadence maps of the plane-of-the-sky projection
of B, via Alfvénic wave tracking (Ref. [2]).
This, in other words, is an imaging method for determining BPOS, the
plane-of-the sky field intensity.
Figure 1 illustrates the
[https://www2.hao.ucar.edu/mlso/instruments/upgraded-coronal-multi-channel-polarimeter CoMP]
view of the global corona, showing its full image capability.

[[File:534f1.png|center|thumb|700px|caption|Figure 1: 
A snapshot view of
[https://www2.hao.ucar.edu/mlso/instruments/upgraded-coronal-multi-channel-polarimeter CoMP]
coronal magnetic observations: full coronal images in I, Q, and U, but not so good in V.
]]

== A solution ==

Our study (Ref. [3]) asks whether this Doppler seismology-derived
BPOS can be included in an inverse reconstruction, rather
than being treated as a separate, independent diagnostic. The result
is a new "IQUD" inversion mode where Fe XIII 1074.7/1079.8 nm
IUQ observations are further constrained by a wave-derived B_POS
(the "D" for Doppler-oscillation diagnostic).
The propagating-kink- wave dispersion relation is used in a POS-projected form,
that doesn't
force the field to lie exactly in the plane of sky.
Ref. [3] investigates test cases, showing that IQUD matches ground truth (IQUV)
statistically indistinguishable, aside from degeneracy multiplicity
(IQUD alone returns a 4-fold-degenerate B). Under perturbation,
matches stay above 96% up to reasonable and observationally achievable
relative-uncertainty levels. Inversions still exceeded 77% even at a
fairly adverse uncertainties. In other words, performance is limited
by the usual suspects: LOS integration and the single-point-approximation
that are the bane of remote-sensing the optically thin and highly structured
solar corona.
Figure 2 illustrates the four-fold degeneracy issue for the IQUD inversions,
bearing in mind the two-fold degeneracy of IQUV.

[[File:534f3.png|center|thumb|700px|caption|Figure 2: 
Example of degeneracies in IQUV and IQUD inversions. One 4-times
degenerate magnetic solution is represented, where the blue and red
arrows show degeneracies with respect to the x- and z-planes. Three
representative viewports are selected: (A) A plane-of-sky observer projection,
analogous to a ground-based observation. (B) The same projection
but with the equatorial plane rotated by 90 degrees. (C) Polar north looking
down projection perpendicular to the plane of the sky.
]]

== Conclusion ==

Our IQUD replacement of IQUV holds great promise for improvements in coronal
magnetometry, and we are grateful for the Hawaiian observatories on Mauna
Kea (DKIST) and Mauna Loa (UCoMP) that make this possible.

== References ==

[1] [https://ui.adsabs.harvard.edu/abs/2024SciA...10.1604S "Mapping the Sun's coronal magnetic field using the Zeeman effect"]

[2] [http://adsabs.harvard.edu/abs/2007Sci...317.1192T "Alfvén Waves in the Solar Corona"]

[3] [https://arxiv.org/abs/2607.12846 "Inferring 3D Coronal Magnetic Fields Through Seismology-Assisted Inversions of IQU-only Spectropolarimetric Observations"]

File:534f1.png

2026-09-04T07:43:51Z

Hhudson: Hhudson uploaded a new version of File:534f1.png

A New Route to Coronal Vector Magnetometry

2026-09-04T07:43:21Z

Hhudson: No. 534 initial upload

{{Infobox Nugget |name = Nugget
|title = Trading Stokes V for Wave Speeds: A New Route to Vector Coronal
Magnetometry
|number = 534
|first_author = Alin PARASCHIV
|publish_date = September 1, 2026
|next_nugget =
|previous_nugget = {{#ask: [[Category:Nugget]] [[RHESSI Nugget Index::532]]}}
}}

== Introduction ==

The magnetic field of the solar corona remains observationally elusive.
At the same time, it is absolutely the most fundamental property defining all
coronal activity.
One of the best approaches to characterizing the field is exploitation of the magnetic sensitivity of the
[https://en.wikipedia.org/wiki/Forbidden_mechanism forbidden]
Fe XIII coronal emission lines in the near infrared.
For a long time, the rule in coronal magnetism seemed simple: if
you wanted the full three-dimensional magnetic field in the corona
you needed the complete polarization signal, in two different
spectral lines.
Coronal light generally carries a polarization fingerprint
that encodes information about the magnetic field, described with
four so-called
[https://en.wikipedia.org/wiki/Stokes_parameters Stokes parameters],
I, Q, U, and V.
The V parameter is the circular polarization, which can be very strong
at radio wavelengths but which is very weak in the visible band.

== Getting at the Stokes parameters ==

The I parameter is just the total intensity;
the linear polarization (Q, U) can come from from
the saturated [https://en.wikipedia.org/wiki/Hanle_effect Hanle effect]
is measurable with current coronal
instruments but is sensitive to the field orientation only.
The circular polarization from the weak-field
[https://nationalmaglab.org/magnet-academy/history-of-electricity-magnetism/museum/zeeman-effect-1896/ Zeeman effect] (Stokes V)
is significantly harder to measure, while being critically needed for
measuring the field strength.
Measurements demand large apertures and
excellent SNR.
Only the [https://en.wikipedia.org/wiki/Daniel_K._Inouye_Solar_Telescope DKIST]
[https://nso.edu/telescopes/dkist/instruments/cryo-nirsp/ Cryo-NIRSP] instrument
has thoroughly delivered on such
measurements so far (Ref. [1]); meanwhile, wide-FOV, small-
aperture instruments like
[https://www2.hao.ucar.edu/mlso/instruments/upgraded-coronal-multi-channel-polarimeter CoMP/UCoMP]
can't realistically chase Stokes V, even
though they are the instruments capable of producing large-
scale, high-cadence maps of the plane-of-the-sky projection
of B, via Alfvénic wave tracking (Ref. [2]).
This, in other words, is an imaging method for determining BPOS, the
plane-of-the sky field intensity.
Figure 1 illustrates the
[https://www2.hao.ucar.edu/mlso/instruments/upgraded-coronal-multi-channel-polarimeter CoMP]
view of the global corona, showing its full image capability.

[[File:534f1.png|center|thumb|700px|caption|Figure 1: 
A snapshot view of
[https://www2.hao.ucar.edu/mlso/instruments/upgraded-coronal-multi-channel-polarimeter CoMP]
coronal magnetic observations.
]]

== A solution ==

Our study (Ref. [3]) asks whether this Doppler seismology-derived
BPOS can be included in an inverse reconstruction, rather
than being treated as a separate, independent diagnostic. The result
is a new "IQUD" inversion mode where Fe XIII 1074.7/1079.8 nm
IUQ observations are further constrained by a wave-derived B_POS
(the "D" for Doppler-oscillation diagnostic).
The propagating-kink- wave dispersion relation is used in a POS-projected form,
that doesn't
force the field to lie exactly in the plane of sky.
Ref. [3] investigates test cases, showing that IQUD matches ground truth (IQUV)
statistically indistinguishable, aside from degeneracy multiplicity
(IQUD alone returns a 4-fold-degenerate B). Under perturbation,
matches stay above 96% up to reasonable and observationally achievable
relative-uncertainty levels. Inversions still exceeded 77% even at a
fairly adverse uncertainties. In other words, performance is limited
by the usual suspects: LOS integration and the single-point-approximation
that are the bane of remote-sensing the optically thin and highly structured
solar corona.
Figure 2 illustrates the four-fold degeneracy issue for the IQUD inversions,
bearing in mind the two-fold degeneracy of IQUV.

[[File:534f3.png|center|thumb|700px|caption|Figure 2: 
Example of degeneracies in IQUV and IQUD inversions. One 4-times
degenerate magnetic solution is represented, where the blue and red
arrows show degeneracies with respect to the x- and z-planes. Three
representative viewports are selected: (A) A plane-of-sky observer projection,
analogous to a ground-based observation. (B) The same projection
but with the equatorial plane rotated by 90 degrees. (C) Polar north looking
down projection perpendicular to the plane of the sky.
]]

== Conclusion ==

Our IQUD replacement of IQUV holds great promise for improvements in coronal
magnetometry, and we are grateful for the Hawaiian observatories on Mauna
Kea (DKIST) and Mauna Loa (UCoMP) that make this possible.

== References ==

[1] [https://ui.adsabs.harvard.edu/abs/2024SciA...10.1604S "Mapping the Sun's coronal magnetic field using the Zeeman effect"]

[2] [http://adsabs.harvard.edu/abs/2007Sci...317.1192T "Alfvén Waves in the Solar Corona"]

[3] [https://arxiv.org/abs/2607.12846 "Inferring 3D Coronal Magnetic Fields Through Seismology-Assisted Inversions of IQU-only Spectropolarimetric Observations"]

Trading Stokes V for Wave Speeds: A New Route to Vector Coronal Magnetometry

2026-09-03T15:33:36Z

Hhudson:

{{Infobox Nugget |name = Nugget
|title = Trading Stokes V for Wave Speeds: A New Route to Vector Coronal
Magnetometry
|number = 534
|first_author = Alin PARASCHIV
|publish_date = September 1, 2026
|next_nugget =
|previous_nugget = {{#ask: [[Category:Nugget]] [[RHESSI Nugget Index::532]]}}
}}

== Introduction ==

The magnetic field of the solar corona remains observationally elusive.
At the same time, it is absolutely the most fundamental property defining all
coronal activity.
One of the best approaches to characterizing the field is exploitation of the magnetic sensitivity of the
[https://en.wikipedia.org/wiki/Forbidden_mechanism forbidden]
Fe XIII coronal emission lines in the near infrared.
For a long time, the rule in coronal magnetism seemed simple: if
you wanted the full three-dimensional magnetic field in the corona
you needed the complete polarization signal, in two different
spectral lines.
Coronal light generally carries a polarization fingerprint
that encodes information about the magnetic field, described with
four so-called
[https://en.wikipedia.org/wiki/Stokes_parameters Stokes parameters],
I, Q, U, and V.
The V parameter is the circular polarization, which can be very strong
at radio wavelengths but which is very weak in the visible band.

== Getting at the Stokes parameters ==

The I parameter is just the total intensity;
the linear polarization (Q, U) can come from from
the saturated [https://en.wikipedia.org/wiki/Hanle_effect Hanle effect]
is measurable with current coronal
instruments but is sensitive to the field orientation only.
The circular polarization from the weak-field
[https://nationalmaglab.org/magnet-academy/history-of-electricity-magnetism/museum/zeeman-effect-1896/ Zeeman effect] (Stokes V)
is significantly harder to measure, while being critically needed for
measuring the field strength.
Measurements demand large apertures and
excellent SNR.
Only the [https://en.wikipedia.org/wiki/Daniel_K._Inouye_Solar_Telescope DKIST]
[https://nso.edu/telescopes/dkist/instruments/cryo-nirsp/ Cryo-NIRSP] instrument
has thoroughly delivered on such
measurements so far (Ref. [1]); meanwhile, wide-FOV, small-
aperture instruments like
[https://www2.hao.ucar.edu/mlso/instruments/upgraded-coronal-multi-channel-polarimeter CoMP/UCoMP]
can't realistically chase Stokes V, even
though they are the instruments capable of producing large-
scale, high-cadence maps of the plane-of-the-sky projection
of B, via Alfvénic wave tracking (Ref. [2]).
This, in other words, is an imaging method for determining BPOS, the
plane-of-the sky field intensity.

== A solution ==

Our study (Ref. [3]) asks whether this Doppler seismology-derived
BPOS can be included in an inverse reconstruction, rather
than being treated as a separate, independent diagnostic. The result
is a new "IQUD" inversion mode where Fe XIII 1074.7/1079.8 nm
IUQ observations are further constrained by a wave-derived B_POS
(the "D" for Doppler-oscillation diagnostic).
The propagating-kink- wave dispersion relation is used in a POS-projected form,
that doesn't
force the field to lie exactly in the plane of sky.
Ref. [3] investigates test cases, showing that IQUD matches ground truth (IQUV)
statistically indistinguishable, aside from degeneracy multiplicity
(IQUD alone returns a 4-fold-degenerate B). Under perturbation,
matches stay above 96% up to reasonable and observationally achievable
relative-uncertainty levels. Inversions still exceeded 77% even at a
fairly adverse uncertainties. In other words, performance is limited
by the usual suspects: LOS integration and the single-point-approximation
that are the bane of remote-sensing the optically thin and highly structured
solar corona.
Figure 1 illustrates the four-fold degeneracy issue for the IQUD inversions.

[[File:534f3.png|center|thumb|700px|caption|Figure 1: 
Example of degeneracies in IQUV and IQUD inversions. One 4-times
degenerate magnetic solution is represented, where the blue and red
arrows show degeneracies with respect to the x- and z-planes. Three
representative viewports are selected: (A) A plane-of-sky observer projection,
analogous to a ground-based observation. (B) The same projection
but with the equatorial plane rotated by 90 degrees. (C) Polar north looking
down projection perpendicular to the plane of the sky.
]]

== Conclusion ==

Our IQUD replacement of IQUV holds great promise for improvements in coronal
magnetometry, and we are grateful for the Hawaiian observatories on Mauna
Kea (DKIST) and Mauna Loa (UCoMP) that make this possible.

== References ==

[1] [https://ui.adsabs.harvard.edu/abs/2024SciA...10.1604S "Mapping the Sun's coronal magnetic field using the Zeeman effect"]

[2] [http://adsabs.harvard.edu/abs/2007Sci...317.1192T "Alfvén Waves in the Solar Corona"]

[3] [https://arxiv.org/abs/2607.12846 "Inferring 3D Coronal Magnetic Fields Through Seismology-Assisted Inversions of IQU-only Spectropolarimetric Observations"]

The Variance of Solar X-ray Flux

2026-09-03T15:33:03Z

Hhudson:

{{Infobox Nugget |name = Nugget
|number = 533
|title = Variance of solar X-ray flux
|first_author = Hugh HUDSON
|publish_date = August 17, 2026
|next_nugget =
|previous_nugget = {{#ask: [[Category:Nugget]] [[RHESSI Nugget Index::532]]}}
}}

== Introduction ==

The time series of solar soft X-ray fluxes has been measured almost
continously since the 1970s, famously by the
[https://www.spaceweather.gov/products/goes-x-ray-flux GOES]
satellite series.
We analyze the timeseries from its 1-8 Å photometers from
the modern GOES-R data, covering the years 2017-2025.

The basic tool used in the analysis is the
[https://mathworld.wolfram.com/PowerSpectrum.html power spectrum],
as inspired by Ref. [1] and a great deal of staring at the timeseries.
These show a somewhat subtle property of the data: the RMS fluctuation,
normalized to the median, tends to be smaller for lower flux levels.
This can be seen real-time (currently) at the
[https://www.astro.gla.ac.uk/users/hsh3f/scratch/fai.html FAI]
("flare anticipation index") link, which shows one-hour intervals.
Note that the variance (and RMS) of this time series is undefined
for long intervals because of the flat power-law occurrence
distribution function of
[https://en.wikipedia.org/wiki/Solar_flare flares] (Ref. [2]),
the dominant source of solar X-ray fluctuations.

== Correlation of variance and mean ==

It turns out that these quantities have a tight correlation, if
assessed over finite time intervals. Figure 1 shows this correlation
for 8 years of recent GOES data, using one-day intervals.

[[File:533_f1.png|center|thumb|600px|caption|Figure 1: 
Variance vs. mean for one-day intervals over 8 years of GOES
soft X-ray (1-8 Å) timeseries, using standard one-minute
sampling.
The diagonal lines show direct proportionality, as would be
expected from
[https://en.wikipedia.org/wiki/Poisson_distribution Poisson statistics].
The X-axis (the means) covers fluxes equivalent to GOES flare classes
AO.1 to X1.
]]

The figure shows clear and systematic deviations from Poisson statistics,
and the correlations fit a power law over the entire dynamic range of
a solar cycle:

var(S) = mean(S)α

where S is the flux and var(S) is its variance. For the 8-year
sample, with no data selection at all, we find α = 3.06 ±. 0.05.
There is no obvious dependence on the solar cycle (Figure 2).

[[File:533f2.png|center|thumb|400px|caption|Figure 1: 
Annual values of the slope parameter α.
]]

The fact that the same power law fits the quiet Sun as well as the flaring Sun suggests
that the flare mechanism is all that one needs to explain.
This result helps to exclude the nanoflare idea for coronal heating (see Ref. [3]).

== Taylor's law ==

This kind of relationship is known as Taylor's law, and I am grateful
to ChatGPT for pointing me to Ref. [2].
It is empirical and describes many natural populations (this particular Taylor studied
ecology), but also many physical systems and even some distributions of
a purely mathematical nature.
The index α follows the physical origin of the distribution:
α > 1 implies correlations or bunching of events, α = 1 implies random
occurrence, and α < 1 implies the suppression of occurrence by an event.
Interestingly the lowest GOES flux levels (2018 in Figure 1) show a
piling-up at the bottom of the scale with this property, probably produced
by the necessarily finite digital levels at the background detection limit
(see the Icon graphic for this Nugget).

== Conclusion ==

This Nugget is based on Ref. [3], and there is just a question about this: do stellar X-ray time series have the same exponent?

== References ==

[1] [http://adsabs.harvard.edu/abs/1991SoPh..133..357H "Solar flares, microflares, nanoflares, and coronal heating"]

[2] [https://ui.adsabs.harvard.edu/abs/1961Natur.189..732T "Aggregation, Variance and the Mean"]

[3] Solar Physics, in review 2026

Trading Stokes V for Wave Speeds: A New Route to Vector Coronal Magnetometry

2026-09-03T15:31:38Z

Hhudson:

{{Infobox Nugget |name = Nugget
|title = Trading Stokes V for Wave Speeds: A New Route to Vector Coronal
Magnetometry
|first_author = Alin PARASCHIV
|publish_date = September 1, 2026
|next_nugget =
|previous_nugget = {{#ask: [[Category:Nugget]] [[RHESSI Nugget Index::532]]}}
}}

== Introduction ==

The magnetic field of the solar corona remains observationally elusive.
At the same time, it is absolutely the most fundamental property defining all
coronal activity.
One of the best approaches to characterizing the field is exploitation of the magnetic sensitivity of the
[https://en.wikipedia.org/wiki/Forbidden_mechanism forbidden]
Fe XIII coronal emission lines in the near infrared.
For a long time, the rule in coronal magnetism seemed simple: if
you wanted the full three-dimensional magnetic field in the corona
you needed the complete polarization signal, in two different
spectral lines.
Coronal light generally carries a polarization fingerprint
that encodes information about the magnetic field, described with
four so-called
[https://en.wikipedia.org/wiki/Stokes_parameters Stokes parameters],
I, Q, U, and V.
The V parameter is the circular polarization, which can be very strong
at radio wavelengths but which is very weak in the visible band.

== Getting at the Stokes parameters ==

The I parameter is just the total intensity;
the linear polarization (Q, U) can come from from
the saturated [https://en.wikipedia.org/wiki/Hanle_effect Hanle effect]
is measurable with current coronal
instruments but is sensitive to the field orientation only.
The circular polarization from the weak-field
[https://nationalmaglab.org/magnet-academy/history-of-electricity-magnetism/museum/zeeman-effect-1896/ Zeeman effect] (Stokes V)
is significantly harder to measure, while being critically needed for
measuring the field strength.
Measurements demand large apertures and
excellent SNR.
Only the [https://en.wikipedia.org/wiki/Daniel_K._Inouye_Solar_Telescope DKIST]
[https://nso.edu/telescopes/dkist/instruments/cryo-nirsp/ Cryo-NIRSP] instrument
has thoroughly delivered on such
measurements so far (Ref. [1]); meanwhile, wide-FOV, small-
aperture instruments like
[https://www2.hao.ucar.edu/mlso/instruments/upgraded-coronal-multi-channel-polarimeter CoMP/UCoMP]
can't realistically chase Stokes V, even
though they are the instruments capable of producing large-
scale, high-cadence maps of the plane-of-the-sky projection
of B, via Alfvénic wave tracking (Ref. [2]).
This, in other words, is an imaging method for determining BPOS, the
plane-of-the sky field intensity.

== A solution ==

Our study (Ref. [3]) asks whether this Doppler seismology-derived
BPOS can be included in an inverse reconstruction, rather
than being treated as a separate, independent diagnostic. The result
is a new "IQUD" inversion mode where Fe XIII 1074.7/1079.8 nm
IUQ observations are further constrained by a wave-derived B_POS
(the "D" for Doppler-oscillation diagnostic).
The propagating-kink- wave dispersion relation is used in a POS-projected form,
that doesn't
force the field to lie exactly in the plane of sky.
Ref. [3] investigates test cases, showing that IQUD matches ground truth (IQUV)
statistically indistinguishable, aside from degeneracy multiplicity
(IQUD alone returns a 4-fold-degenerate B). Under perturbation,
matches stay above 96% up to reasonable and observationally achievable
relative-uncertainty levels. Inversions still exceeded 77% even at a
fairly adverse uncertainties. In other words, performance is limited
by the usual suspects: LOS integration and the single-point-approximation
that are the bane of remote-sensing the optically thin and highly structured
solar corona.
Figure 1 illustrates the four-fold degeneracy issue for the IQUD inversions.

[[File:534f3.png|center|thumb|700px|caption|Figure 1: 
Example of degeneracies in IQUV and IQUD inversions. One 4-times
degenerate magnetic solution is represented, where the blue and red
arrows show degeneracies with respect to the x- and z-planes. Three
representative viewports are selected: (A) A plane-of-sky observer projection,
analogous to a ground-based observation. (B) The same projection
but with the equatorial plane rotated by 90 degrees. (C) Polar north looking
down projection perpendicular to the plane of the sky.
]]

== Conclusion ==

Our IQUD replacement of IQUV holds great promise for improvements in coronal
magnetometry, and we are grateful for the Hawaiian observatories on Mauna
Kea (DKIST) and Mauna Loa (UCoMP) that make this possible.

== References ==

[1] [https://ui.adsabs.harvard.edu/abs/2024SciA...10.1604S "Mapping the Sun's coronal magnetic field using the Zeeman effect"]

[2] [http://adsabs.harvard.edu/abs/2007Sci...317.1192T "Alfvén Waves in the Solar Corona"]

[3] [https://arxiv.org/abs/2607.12846 "Inferring 3D Coronal Magnetic Fields Through Seismology-Assisted Inversions of IQU-only Spectropolarimetric Observations"]

Electron-Ion equilibration in CME-driven shocks

2026-09-03T15:30:41Z

Hhudson:

{{Infobox Nugget |name = Nugget
|title = Electron-Ion equilibration in CME-driven shocks
|first_author = John RAYMOND
|publish_date = August 3, 2026
|number = 532
|next_nugget =
|previous_nugget = {{#ask: [[Category:Nugget]] [[RHESSI Nugget Index::531]]}}
}}

== Introduction ==

Coronal mass ejections
[https://en.wikipedia.org/wiki/Coronal_mass_ejection (CMEs)]
drive shock waves into regions of very low collisionality.
The jumps in density, pressure and temperature at a shock wave in dense
gas are mediated by particle collisions, and that leads to thermal
equilibrium: equal temperatures of all particle species and a Maxwellian
velocity distribution for each species.
In a low density plasma,
on the other hand, the collision lengths are large, and the shock
jump must therefore be mediated by electromagnetic fields and plasma waves.
That can lead to non-Maxwellian velocity distributions, such as Solar
Energetic Particles (SEPs), and to differing electron and ion
temperatures.

In the solar wind, postshock electron temperatures are generally
less than proton temperatures (e.g., Ref. [1])
though there is considerable scatter.
Shocks in supernova
remnants reach higher Mach numbers, and they show a trend
of decreasing electron-to-ion temperature ratio with increasing
shock speed or Mach number (Ref. [2]). CME-driven shocks
In the solar corona are more difficult to study, but they are
observed as type II radio bursts and as faint emission in UV, EUV
and white light coronagraph spectra and images (e.g., Ref. [3]).

== How do we infer plasma temperatures? ==

In some cases, it is possible to infer the electron temperature
behind a coronal shock by comparing extreme ultraviolet images from
[https://aia.lmsal.com AIA] in different bands.
When the electrons are suddenly heated in a shock, the iron ions
are successively ionized from Fe X to Fe XII to Fe XIV to Fe XVI
(The AIA 171, 193, 211 and 335 Å bands).
If the density is known from
[https://en.wikipedia.org/wiki/Solar_radio_emission type II]
radio emission or from a global MHD model of the corona, the lags
between the appearance of the shock in the
different bands indicate the electron temperature (Refs. [4,5]).
Figure 1 shows a CME-driven shock observed
on 2010 June 13, with the 3D structure inferred from AIA and STEREO
images (Ref. [5]).
Figure 2 shows the dimensionless
parameter ΔTe at different positions along the shock front,
where ΔTe = 0 corresponds to equal electron and proton
temperatures and ΔTe = 1 corresponds to no electron heating.
The intermediate values seen in Figure 2 show that these 500-700 km/s
shocks heat the electrons about half as efficiently as the ions.

[[File:532f1.png|center|thumb|600px|caption|Figure 1: 
SDO/AIA 193 Å running difference images at three different times of
the 13 June 2010 CME-driven shock wave. The blue line shows the
outline of the geometric model - here, the data were binned by a
factor of 8 to increase the S/N when fitting the model to the data.
The software captures the irregular shape of the shock, accounting
for angle-dependent acceleration. The shock can be identified as
the bright outer ring of the structure, while the erupting prominence
driving the shock is clearly identified as the bright inner ring
structure. Bottom: Corresponding STEREO-A EUVI 195 Å difference
images, with the geometric model plotted in blue. Right: Labeled
reference of different portions of the shock structure.
]]

[[File:532f2.png|center|thumb|600px|caption|Figure 2: 

A schematic map of the shock, with separate regions highlighted in yellow, magenta, and/or cyan
based on the performance of each model based on the time of the
peaks and the intensities of the peaks. Panels showing the combined
color maps use a CMY subtractive color model to accurately reflect
where the data is unable to differentiate between the models. The
color wheel at the top-right serves as an approximate guide, where
the color changes depending on the separation from the loci for
each model. The solid blue hexagon, for instance, represents good
agreement with both ΔTe = 0.5 (cyan) and
ΔTe = 0.25 (magenta) models
where ΔTe = 0 for complete equilibration and 1 for no
equilibration.
]]

== Conclusion ==

Non-equilibrium plasmas probably dominate the Universe, but they are hard to diagnose via remote-sensing
techniques.
A wealth of plasma physics results from Te ≠ Ti and anisotropic distribution functions,
and large-scale shock waves in the solar corona provide an excellent opportunity to study such effects.

== References ==

[1] [https://ui.adsabs.harvard.edu/abs/2013SSRv..178..633G "Electron-Ion Temperature Equilibration in Collisionless Shocks: The Supernova Remnant-Solar Wind Connection"]

[2] [https://ui.adsabs.harvard.edu/abs/2023ApJ...949...50R "Electron-Ion Temperature Ratio in Astrophysical Shocks"]

[3] [http://adsabs.harvard.edu/abs/2004A%26A...413..363M "Coronal transients and metric type II radio bursts. I. Effects of geometry"]

[4] [https://ui.adsabs.harvard.edu/abs/2011ApJ...738..160M "Observations and Interpretation of a Low Coronal Shock Wave Observed in the EUV by the SDO/AIA"]

[5] [https://ui.adsabs.harvard.edu/abs/2025ApJ...989..175T "A 3D Nonequilibrium Ionization Model of a Shock Wave in the Low Corona. I. Extreme-ultraviolet Emission and Inefficient Electron Heating"]

Trading Stokes V for Wave Speeds: A New Route to Vector Coronal Magnetometry

2026-09-03T15:00:07Z

Hhudson: /* Getting at the Stokes parameters */

{{Infobox Nugget |name = Nugget
|title = Trading Stokes V for Wave Speeds: A New Route to Vector Coronal
Magnetometry
|first_author = Alin PARASCHIV
|publish_date = September 1, 2026
|next_nugget =
|previous_nugget = {{#ask: [[Category:Nugget]] [[RHESSI Nugget Index::533]]}}
}}

== Introduction ==

The magnetic field of the solar corona remains observationally elusive.
At the same time, it is absolutely the most fundamental property defining all
coronal activity.
One of the best approaches to characterizing the field is exploitation of the magnetic sensitivity of the
[https://en.wikipedia.org/wiki/Forbidden_mechanism forbidden]
Fe XIII coronal emission lines in the near infrared.
For a long time, the rule in coronal magnetism seemed simple: if
you wanted the full three-dimensional magnetic field in the corona
you needed the complete polarization signal, in two different
spectral lines.
Coronal light generally carries a polarization fingerprint
that encodes information about the magnetic field, described with
four so-called
[https://en.wikipedia.org/wiki/Stokes_parameters Stokes parameters],
I, Q, U, and V.
The V parameter is the circular polarization, which can be very strong
at radio wavelengths but which is very weak in the visible band.

== Getting at the Stokes parameters ==

The I parameter is just the total intensity;
the linear polarization (Q, U) can come from from
the saturated [https://en.wikipedia.org/wiki/Hanle_effect Hanle effect]
is measurable with current coronal
instruments but is sensitive to the field orientation only.
The circular polarization from the weak-field
[https://nationalmaglab.org/magnet-academy/history-of-electricity-magnetism/museum/zeeman-effect-1896/ Zeeman effect] (Stokes V)
is significantly harder to measure, while being critically needed for
measuring the field strength.
Measurements demand large apertures and
excellent SNR.
Only the [https://en.wikipedia.org/wiki/Daniel_K._Inouye_Solar_Telescope DKIST]
[https://nso.edu/telescopes/dkist/instruments/cryo-nirsp/ Cryo-NIRSP] instrument
has thoroughly delivered on such
measurements so far (Ref. [1]); meanwhile, wide-FOV, small-
aperture instruments like
[https://www2.hao.ucar.edu/mlso/instruments/upgraded-coronal-multi-channel-polarimeter CoMP/UCoMP]
can't realistically chase Stokes V, even
though they are the instruments capable of producing large-
scale, high-cadence maps of the plane-of-the-sky projection
of B, via Alfvénic wave tracking (Ref. [2]).
This, in other words, is an imaging method for determining BPOS, the
plane-of-the sky field intensity.

== A solution ==

Our study (Ref. [3]) asks whether this Doppler seismology-derived
BPOS can be included in an inverse reconstruction, rather
than being treated as a separate, independent diagnostic. The result
is a new "IQUD" inversion mode where Fe XIII 1074.7/1079.8 nm
IUQ observations are further constrained by a wave-derived B_POS
(the "D" for Doppler-oscillation diagnostic).
The propagating-kink- wave dispersion relation is used in a POS-projected form,
that doesn't
force the field to lie exactly in the plane of sky.
Ref. [3] investigates test cases, showing that IQUD matches ground truth (IQUV)
statistically indistinguishable, aside from degeneracy multiplicity
(IQUD alone returns a 4-fold-degenerate B). Under perturbation,
matches stay above 96% up to reasonable and observationally achievable
relative-uncertainty levels. Inversions still exceeded 77% even at a
fairly adverse uncertainties. In other words, performance is limited
by the usual suspects: LOS integration and the single-point-approximation
that are the bane of remote-sensing the optically thin and highly structured
solar corona.
Figure 1 illustrates the four-fold degeneracy issue for the IQUD inversions.

[[File:534f3.png|center|thumb|700px|caption|Figure 1: 
Example of degeneracies in IQUV and IQUD inversions. One 4-times
degenerate magnetic solution is represented, where the blue and red
arrows show degeneracies with respect to the x- and z-planes. Three
representative viewports are selected: (A) A plane-of-sky observer projection,
analogous to a ground-based observation. (B) The same projection
but with the equatorial plane rotated by 90 degrees. (C) Polar north looking
down projection perpendicular to the plane of the sky.
]]

== Conclusion ==

Our IQUD replacement of IQUV holds great promise for improvements in coronal
magnetometry, and we are grateful for the Hawaiian observatories on Mauna
Kea (DKIST) and Mauna Loa (UCoMP) that make this possible.

== References ==

[1] [https://ui.adsabs.harvard.edu/abs/2024SciA...10.1604S "Mapping the Sun's coronal magnetic field using the Zeeman effect"]

[2] [http://adsabs.harvard.edu/abs/2007Sci...317.1192T "Alfvén Waves in the Solar Corona"]

[3] [https://arxiv.org/abs/2607.12846 "Inferring 3D Coronal Magnetic Fields Through Seismology-Assisted Inversions of IQU-only Spectropolarimetric Observations"]

Trading Stokes V for Wave Speeds: A New Route to Vector Coronal Magnetometry

2026-09-03T14:59:12Z

Hhudson: /* Getting at the Stokes parameters */

{{Infobox Nugget |name = Nugget
|title = Trading Stokes V for Wave Speeds: A New Route to Vector Coronal
Magnetometry
|first_author = Alin PARASCHIV
|publish_date = September 1, 2026
|next_nugget =
|previous_nugget = {{#ask: [[Category:Nugget]] [[RHESSI Nugget Index::533]]}}
}}

== Introduction ==

The magnetic field of the solar corona remains observationally elusive.
At the same time, it is absolutely the most fundamental property defining all
coronal activity.
One of the best approaches to characterizing the field is exploitation of the magnetic sensitivity of the
[https://en.wikipedia.org/wiki/Forbidden_mechanism forbidden]
Fe XIII coronal emission lines in the near infrared.
For a long time, the rule in coronal magnetism seemed simple: if
you wanted the full three-dimensional magnetic field in the corona
you needed the complete polarization signal, in two different
spectral lines.
Coronal light generally carries a polarization fingerprint
that encodes information about the magnetic field, described with
four so-called
[https://en.wikipedia.org/wiki/Stokes_parameters Stokes parameters],
I, Q, U, and V.
The V parameter is the circular polarization, which can be very strong
at radio wavelengths but which is very weak in the visible band.

== Getting at the Stokes parameters ==

The I parameter is just the total intensity;
the linear polarization (Q, U) can come from from
the saturated [https://en.wikipedia.org/wiki/Hanle_effect Hanle effect]
is measurable with current coronal
instruments but is sensitive to the field orientation only.
The circular polarization from the weak-field
[https://nationalmaglab.org/magnet-academy/history-of-electricity-magnetism/museum/zeeman-effect-1896/ Zeeman effect] (Stokes V)
is significantly harder to measure, while being critically needed for
measuring the field strength.
Measurements demand large apertures and
excellent SNR.
Only the [https://en.wikipedia.org/wiki/Daniel_K._Inouye_Solar_Telescope DKIST]
[https://nso.edu/telescopes/dkist/instruments/cryo-nirsp/ Cryo-NIRSP] instrument
has thoroughly delivered on such
measurements so far (Ref. [1]); meanwhile, wide-FOV, small-
aperture instruments like
[https://www2.hao.ucar.edu/mlso/instruments/upgraded-coronal-multi-channel-polarimeter CoMP/UCoMP]
can't realistically chase Stokes V, even
though they are the instruments capable of producing large-
scale, high-cadence maps of the plane-of-the-sky projection
of B, via Alfvénic wave tracking(Ref. [2]).
This, in other words, is an imaging method for determining BPOS, the
plane-of-the sky field intensity.

== A solution ==

Our study (Ref. [3]) asks whether this Doppler seismology-derived
BPOS can be included in an inverse reconstruction, rather
than being treated as a separate, independent diagnostic. The result
is a new "IQUD" inversion mode where Fe XIII 1074.7/1079.8 nm
IUQ observations are further constrained by a wave-derived B_POS
(the "D" for Doppler-oscillation diagnostic).
The propagating-kink- wave dispersion relation is used in a POS-projected form,
that doesn't
force the field to lie exactly in the plane of sky.
Ref. [3] investigates test cases, showing that IQUD matches ground truth (IQUV)
statistically indistinguishable, aside from degeneracy multiplicity
(IQUD alone returns a 4-fold-degenerate B). Under perturbation,
matches stay above 96% up to reasonable and observationally achievable
relative-uncertainty levels. Inversions still exceeded 77% even at a
fairly adverse uncertainties. In other words, performance is limited
by the usual suspects: LOS integration and the single-point-approximation
that are the bane of remote-sensing the optically thin and highly structured
solar corona.
Figure 1 illustrates the four-fold degeneracy issue for the IQUD inversions.

[[File:534f3.png|center|thumb|700px|caption|Figure 1: 
Example of degeneracies in IQUV and IQUD inversions. One 4-times
degenerate magnetic solution is represented, where the blue and red
arrows show degeneracies with respect to the x- and z-planes. Three
representative viewports are selected: (A) A plane-of-sky observer projection,
analogous to a ground-based observation. (B) The same projection
but with the equatorial plane rotated by 90 degrees. (C) Polar north looking
down projection perpendicular to the plane of the sky.
]]

== Conclusion ==

Our IQUD replacement of IQUV holds great promise for improvements in coronal
magnetometry, and we are grateful for the Hawaiian observatories on Mauna
Kea (DKIST) and Mauna Loa (UCoMP) that make this possible.

== References ==

[1] [https://ui.adsabs.harvard.edu/abs/2024SciA...10.1604S "Mapping the Sun's coronal magnetic field using the Zeeman effect"]

[2] [http://adsabs.harvard.edu/abs/2007Sci...317.1192T "Alfvén Waves in the Solar Corona"]

[3] [https://arxiv.org/abs/2607.12846 "Inferring 3D Coronal Magnetic Fields Through Seismology-Assisted Inversions of IQU-only Spectropolarimetric Observations"]

Trading Stokes V for Wave Speeds: A New Route to Vector Coronal Magnetometry

2026-09-03T14:58:13Z

Hhudson: /* Conclusion */

{{Infobox Nugget |name = Nugget
|title = Trading Stokes V for Wave Speeds: A New Route to Vector Coronal
Magnetometry
|first_author = Alin PARASCHIV
|publish_date = September 1, 2026
|next_nugget =
|previous_nugget = {{#ask: [[Category:Nugget]] [[RHESSI Nugget Index::533]]}}
}}

== Introduction ==

The magnetic field of the solar corona remains observationally elusive.
At the same time, it is absolutely the most fundamental property defining all
coronal activity.
One of the best approaches to characterizing the field is exploitation of the magnetic sensitivity of the
[https://en.wikipedia.org/wiki/Forbidden_mechanism forbidden]
Fe XIII coronal emission lines in the near infrared.
For a long time, the rule in coronal magnetism seemed simple: if
you wanted the full three-dimensional magnetic field in the corona
you needed the complete polarization signal, in two different
spectral lines.
Coronal light generally carries a polarization fingerprint
that encodes information about the magnetic field, described with
four so-called
[https://en.wikipedia.org/wiki/Stokes_parameters Stokes parameters],
I, Q, U, and V.
The V parameter is the circular polarization, which can be very strong
at radio wavelengths but which is very weak in the visible band.

== Getting at the Stokes parameters ==

The I parameter is just the total intensity;
the linear polarization (Q, U) can come from from
the saturated [https://en.wikipedia.org/wiki/Hanle_effect Hanle effect]
is measurable with current coronal
instruments but is sensitive to the field orientation only.
The circular polarization from the weak-field
[https://nationalmaglab.org/magnet-academy/history-of-electricity-magnetism/museum/zeeman-effect-1896/ Zeeman effect] (Stokes V)
is significantly harder to measure, while being critically needed for
measuring the field strength.
Measurements demand large apertures and
excellent SNR.
Only the [https://en.wikipedia.org/wiki/Daniel_K._Inouye_Solar_Telescope DKIST]
[https://nso.edu/telescopes/dkist/instruments/cryo-nirsp/ Cryo-NIRSP instrument
has thoroughly delivered on such
measurements so far (Ref. [1]); meanwhile, wide-FOV, small-
aperture instruments like
[https://www2.hao.ucar.edu/mlso/instruments/upgraded-coronal-multi-channel-polarimeter CoMP/UCoMP]
can't realistically chase Stokes V, even
though they are the instruments capable of producing large-
scale, high-cadence maps of the plane-of-the-sky projection
of B, via Alfvénic wave tracking(Ref. [2]).
This, in other words, is an imaging method for determining BPOS, the
plane-of-the sky field intensity.

== A solution ==

Our study (Ref. [3]) asks whether this Doppler seismology-derived
BPOS can be included in an inverse reconstruction, rather
than being treated as a separate, independent diagnostic. The result
is a new "IQUD" inversion mode where Fe XIII 1074.7/1079.8 nm
IUQ observations are further constrained by a wave-derived B_POS
(the "D" for Doppler-oscillation diagnostic).
The propagating-kink- wave dispersion relation is used in a POS-projected form,
that doesn't
force the field to lie exactly in the plane of sky.
Ref. [3] investigates test cases, showing that IQUD matches ground truth (IQUV)
statistically indistinguishable, aside from degeneracy multiplicity
(IQUD alone returns a 4-fold-degenerate B). Under perturbation,
matches stay above 96% up to reasonable and observationally achievable
relative-uncertainty levels. Inversions still exceeded 77% even at a
fairly adverse uncertainties. In other words, performance is limited
by the usual suspects: LOS integration and the single-point-approximation
that are the bane of remote-sensing the optically thin and highly structured
solar corona.
Figure 1 illustrates the four-fold degeneracy issue for the IQUD inversions.

[[File:534f3.png|center|thumb|700px|caption|Figure 1: 
Example of degeneracies in IQUV and IQUD inversions. One 4-times
degenerate magnetic solution is represented, where the blue and red
arrows show degeneracies with respect to the x- and z-planes. Three
representative viewports are selected: (A) A plane-of-sky observer projection,
analogous to a ground-based observation. (B) The same projection
but with the equatorial plane rotated by 90 degrees. (C) Polar north looking
down projection perpendicular to the plane of the sky.
]]

== Conclusion ==

Our IQUD replacement of IQUV holds great promise for improvements in coronal
magnetometry, and we are grateful for the Hawaiian observatories on Mauna
Kea (DKIST) and Mauna Loa (UCoMP) that make this possible.

== References ==

[1] [https://ui.adsabs.harvard.edu/abs/2024SciA...10.1604S "Mapping the Sun's coronal magnetic field using the Zeeman effect"]

[2] [http://adsabs.harvard.edu/abs/2007Sci...317.1192T "Alfvén Waves in the Solar Corona"]

[3] [https://arxiv.org/abs/2607.12846 "Inferring 3D Coronal Magnetic Fields Through Seismology-Assisted Inversions of IQU-only Spectropolarimetric Observations"]

Trading Stokes V for Wave Speeds: A New Route to Vector Coronal Magnetometry

2026-09-03T14:57:29Z

Hhudson: Created page with "{{Infobox Nugget |name = Nugget |title = Trading Stokes V for Wave Speeds: A New Route to Vector Coronal Magnetometry |first_author = Alin PARASCHIV |publish_date = September 1, 2026 |next_nugget = |previous_nugget = {{#ask: Category:Nugget RHESSI Nugget Index::533}} }} == Introduction == The magnetic field of the solar corona remains observationally elusive. At the same time, it is absolutely the most fundamental property defining all coronal activity. One o..."

{{Infobox Nugget |name = Nugget
|title = Trading Stokes V for Wave Speeds: A New Route to Vector Coronal
Magnetometry
|first_author = Alin PARASCHIV
|publish_date = September 1, 2026
|next_nugget =
|previous_nugget = {{#ask: [[Category:Nugget]] [[RHESSI Nugget Index::533]]}}
}}

== Introduction ==

The magnetic field of the solar corona remains observationally elusive.
At the same time, it is absolutely the most fundamental property defining all
coronal activity.
One of the best approaches to characterizing the field is exploitation of the magnetic sensitivity of the
[https://en.wikipedia.org/wiki/Forbidden_mechanism forbidden]
Fe XIII coronal emission lines in the near infrared.
For a long time, the rule in coronal magnetism seemed simple: if
you wanted the full three-dimensional magnetic field in the corona
you needed the complete polarization signal, in two different
spectral lines.
Coronal light generally carries a polarization fingerprint
that encodes information about the magnetic field, described with
four so-called
[https://en.wikipedia.org/wiki/Stokes_parameters Stokes parameters],
I, Q, U, and V.
The V parameter is the circular polarization, which can be very strong
at radio wavelengths but which is very weak in the visible band.

== Getting at the Stokes parameters ==

The I parameter is just the total intensity;
the linear polarization (Q, U) can come from from
the saturated [https://en.wikipedia.org/wiki/Hanle_effect Hanle effect]
is measurable with current coronal
instruments but is sensitive to the field orientation only.
The circular polarization from the weak-field
[https://nationalmaglab.org/magnet-academy/history-of-electricity-magnetism/museum/zeeman-effect-1896/ Zeeman effect] (Stokes V)
is significantly harder to measure, while being critically needed for
measuring the field strength.
Measurements demand large apertures and
excellent SNR.
Only the [https://en.wikipedia.org/wiki/Daniel_K._Inouye_Solar_Telescope DKIST]
[https://nso.edu/telescopes/dkist/instruments/cryo-nirsp/ Cryo-NIRSP instrument
has thoroughly delivered on such
measurements so far (Ref. [1]); meanwhile, wide-FOV, small-
aperture instruments like
[https://www2.hao.ucar.edu/mlso/instruments/upgraded-coronal-multi-channel-polarimeter CoMP/UCoMP]
can't realistically chase Stokes V, even
though they are the instruments capable of producing large-
scale, high-cadence maps of the plane-of-the-sky projection
of B, via Alfvénic wave tracking(Ref. [2]).
This, in other words, is an imaging method for determining BPOS, the
plane-of-the sky field intensity.

== A solution ==

Our study (Ref. [3]) asks whether this Doppler seismology-derived
BPOS can be included in an inverse reconstruction, rather
than being treated as a separate, independent diagnostic. The result
is a new "IQUD" inversion mode where Fe XIII 1074.7/1079.8 nm
IUQ observations are further constrained by a wave-derived B_POS
(the "D" for Doppler-oscillation diagnostic).
The propagating-kink- wave dispersion relation is used in a POS-projected form,
that doesn't
force the field to lie exactly in the plane of sky.
Ref. [3] investigates test cases, showing that IQUD matches ground truth (IQUV)
statistically indistinguishable, aside from degeneracy multiplicity
(IQUD alone returns a 4-fold-degenerate B). Under perturbation,
matches stay above 96% up to reasonable and observationally achievable
relative-uncertainty levels. Inversions still exceeded 77% even at a
fairly adverse uncertainties. In other words, performance is limited
by the usual suspects: LOS integration and the single-point-approximation
that are the bane of remote-sensing the optically thin and highly structured
solar corona.
Figure 1 illustrates the four-fold degeneracy issue for the IQUD inversions.

[[File:534f3.png|center|thumb|700px|caption|Figure 1: 
Example of degeneracies in IQUV and IQUD inversions. One 4-times
degenerate magnetic solution is represented, where the blue and red
arrows show degeneracies with respect to the x- and z-planes. Three
representative viewports are selected: (A) A plane-of-sky observer projection,
analogous to a ground-based observation. (B) The same projection
but with the equatorial plane rotated by 90 degrees. (C) Polar north looking
down projection perpendicular to the plane of the sky.
]]

== Conclusion ==

Our IQUD replacement of IQUV holds great promise for improvements in coronal
magnetometry, and we are grateful for the the Hawaiian observatories on Mauna
Kea (DKIST) and Mauna Loa (UCoMP) that make this possible.

== References ==

[1] [https://ui.adsabs.harvard.edu/abs/2024SciA...10.1604S "Mapping the Sun's coronal magnetic field using the Zeeman effect"]

[2] [http://adsabs.harvard.edu/abs/2007Sci...317.1192T "Alfvén Waves in the Solar Corona"]

[3] [https://arxiv.org/abs/2607.12846 "Inferring 3D Coronal Magnetic Fields Through Seismology-Assisted Inversions of IQU-only Spectropolarimetric Observations"]

The Variance of Solar X-ray Flux

2026-08-27T15:01:55Z

Hhudson: /* Taylor's law */

{{Infobox Nugget |name = Nugget
|title = Variance of solar X-ray flux
|first_author = Hugh HUDSON
|publish_date = August 17, 2026
|next_nugget =
|previous_nugget = {{#ask: [[Category:Nugget]] [[RHESSI Nugget Index::532]]}}
}}

== Introduction ==

The time series of solar soft X-ray fluxes has been measured almost
continously since the 1970s, famously by the
[https://www.spaceweather.gov/products/goes-x-ray-flux GOES]
satellite series.
We analyze the timeseries from its 1-8 Å photometers from
the modern GOES-R data, covering the years 2017-2025.

The basic tool used in the analysis is the
[https://mathworld.wolfram.com/PowerSpectrum.html power spectrum],
as inspired by Ref. [1] and a great deal of staring at the timeseries.
These show a somewhat subtle property of the data: the RMS fluctuation,
normalized to the median, tends to be smaller for lower flux levels.
This can be seen real-time (currently) at the
[https://www.astro.gla.ac.uk/users/hsh3f/scratch/fai.html FAI]
("flare anticipation index") link, which shows one-hour intervals.
Note that the variance (and RMS) of this time series is undefined
for long intervals because of the flat power-law occurrence
distribution function of
[https://en.wikipedia.org/wiki/Solar_flare flares] (Ref. [2]),
the dominant source of solar X-ray fluctuations.

== Correlation of variance and mean ==

It turns out that these quantities have a tight correlation, if
assessed over finite time intervals. Figure 1 shows this correlation
for 8 years of recent GOES data, using one-day intervals.

[[File:533_f1.png|center|thumb|600px|caption|Figure 1: 
Variance vs. mean for one-day intervals over 8 years of GOES
soft X-ray (1-8 Å) timeseries, using standard one-minute
sampling.
The diagonal lines show direct proportionality, as would be
expected from
[https://en.wikipedia.org/wiki/Poisson_distribution Poisson statistics].
The X-axis (the means) covers fluxes equivalent to GOES flare classes
AO.1 to X1.
]]

The figure shows clear and systematic deviations from Poisson statistics,
and the correlations fit a power law over the entire dynamic range of
a solar cycle:

var(S) = mean(S)α

where S is the flux and var(S) is its variance. For the 8-year
sample, with no data selection at all, we find α = 3.06 ±. 0.05.
There is no obvious dependence on the solar cycle (Figure 2).

[[File:533f2.png|center|thumb|400px|caption|Figure 1: 
Annual values of the slope parameter α.
]]

The fact that the same power law fits the quiet Sun as well as the flaring Sun suggests
that the flare mechanism is all that one needs to explain.
This result helps to exclude the nanoflare idea for coronal heating (see Ref. [3]).

== Taylor's law ==

This kind of relationship is known as Taylor's law, and I am grateful
to ChatGPT for pointing me to Ref. [2].
It is empirical and describes many natural populations (this particular Taylor studied
ecology), but also many physical systems and even some distributions of
a purely mathematical nature.
The index α follows the physical origin of the distribution:
α > 1 implies correlations or bunching of events, α = 1 implies random
occurrence, and α < 1 implies the suppression of occurrence by an event.
Interestingly the lowest GOES flux levels (2018 in Figure 1) show a
piling-up at the bottom of the scale with this property, probably produced
by the necessarily finite digital levels at the background detection limit
(see the Icon graphic for this Nugget).

== Conclusion ==

This Nugget is based on Ref. [3], and there is just a question about this: do stellar X-ray time series have the same exponent?

== References ==

[1] [http://adsabs.harvard.edu/abs/1991SoPh..133..357H "Solar flares, microflares, nanoflares, and coronal heating"]

[2] [https://ui.adsabs.harvard.edu/abs/1961Natur.189..732T "Aggregation, Variance and the Mean"]

[3] Solar Physics, in review 2026

The Variance of Solar X-ray Flux

2026-08-27T15:01:06Z

Hhudson: /* Taylor's law */

{{Infobox Nugget |name = Nugget
|title = Variance of solar X-ray flux
|first_author = Hugh HUDSON
|publish_date = August 17, 2026
|next_nugget =
|previous_nugget = {{#ask: [[Category:Nugget]] [[RHESSI Nugget Index::532]]}}
}}

== Introduction ==

The time series of solar soft X-ray fluxes has been measured almost
continously since the 1970s, famously by the
[https://www.spaceweather.gov/products/goes-x-ray-flux GOES]
satellite series.
We analyze the timeseries from its 1-8 Å photometers from
the modern GOES-R data, covering the years 2017-2025.

The basic tool used in the analysis is the
[https://mathworld.wolfram.com/PowerSpectrum.html power spectrum],
as inspired by Ref. [1] and a great deal of staring at the timeseries.
These show a somewhat subtle property of the data: the RMS fluctuation,
normalized to the median, tends to be smaller for lower flux levels.
This can be seen real-time (currently) at the
[https://www.astro.gla.ac.uk/users/hsh3f/scratch/fai.html FAI]
("flare anticipation index") link, which shows one-hour intervals.
Note that the variance (and RMS) of this time series is undefined
for long intervals because of the flat power-law occurrence
distribution function of
[https://en.wikipedia.org/wiki/Solar_flare flares] (Ref. [2]),
the dominant source of solar X-ray fluctuations.

== Correlation of variance and mean ==

It turns out that these quantities have a tight correlation, if
assessed over finite time intervals. Figure 1 shows this correlation
for 8 years of recent GOES data, using one-day intervals.

[[File:533_f1.png|center|thumb|600px|caption|Figure 1: 
Variance vs. mean for one-day intervals over 8 years of GOES
soft X-ray (1-8 Å) timeseries, using standard one-minute
sampling.
The diagonal lines show direct proportionality, as would be
expected from
[https://en.wikipedia.org/wiki/Poisson_distribution Poisson statistics].
The X-axis (the means) covers fluxes equivalent to GOES flare classes
AO.1 to X1.
]]

The figure shows clear and systematic deviations from Poisson statistics,
and the correlations fit a power law over the entire dynamic range of
a solar cycle:

var(S) = mean(S)α

where S is the flux and var(S) is its variance. For the 8-year
sample, with no data selection at all, we find α = 3.06 ±. 0.05.
There is no obvious dependence on the solar cycle (Figure 2).

[[File:533f2.png|center|thumb|400px|caption|Figure 1: 
Annual values of the slope parameter α.
]]

The fact that the same power law fits the quiet Sun as well as the flaring Sun suggests
that the flare mechanism is all that one needs to explain.
This result helps to exclude the nanoflare idea for coronal heating (see Ref. [3]).

== Taylor's law ==

This kind of relationship is known as Taylor's law, and I am grateful
to ChatGPT for pointing me to Ref. [2].
It is empirical and describes many natural populations (this particular Taylor studied
ecology), but also many physical systems and even some distributions of
a purely mathematical nature.
The index α follows the physical origin of the distribution:
α > 1 implies correlations or bunching of events, α = 1 implies random
occurrence, and α < 1 implies the suppression of occurrence by an event.
Interestingly the lowest GOES flux levels (2018 in Figure 1) show a
piling-up at the bottom of the scale with this property, probably produced
by the necessarily finite digital levels at the background detection limit.

== Conclusion ==

This Nugget is based on Ref. [3], and there is just a question about this: do stellar X-ray time series have the same exponent?

== References ==

[1] [http://adsabs.harvard.edu/abs/1991SoPh..133..357H "Solar flares, microflares, nanoflares, and coronal heating"]

[2] [https://ui.adsabs.harvard.edu/abs/1961Natur.189..732T "Aggregation, Variance and the Mean"]

[3] Solar Physics, in review 2026

The Variance of Solar X-ray Flux

2026-08-27T15:00:19Z

Hhudson:

{{Infobox Nugget |name = Nugget
|title = Variance of solar X-ray flux
|first_author = Hugh HUDSON
|publish_date = August 17, 2026
|next_nugget =
|previous_nugget = {{#ask: [[Category:Nugget]] [[RHESSI Nugget Index::532]]}}
}}

== Introduction ==

The time series of solar soft X-ray fluxes has been measured almost
continously since the 1970s, famously by the
[https://www.spaceweather.gov/products/goes-x-ray-flux GOES]
satellite series.
We analyze the timeseries from its 1-8 Å photometers from
the modern GOES-R data, covering the years 2017-2025.

The basic tool used in the analysis is the
[https://mathworld.wolfram.com/PowerSpectrum.html power spectrum],
as inspired by Ref. [1] and a great deal of staring at the timeseries.
These show a somewhat subtle property of the data: the RMS fluctuation,
normalized to the median, tends to be smaller for lower flux levels.
This can be seen real-time (currently) at the
[https://www.astro.gla.ac.uk/users/hsh3f/scratch/fai.html FAI]
("flare anticipation index") link, which shows one-hour intervals.
Note that the variance (and RMS) of this time series is undefined
for long intervals because of the flat power-law occurrence
distribution function of
[https://en.wikipedia.org/wiki/Solar_flare flares] (Ref. [2]),
the dominant source of solar X-ray fluctuations.

== Correlation of variance and mean ==

It turns out that these quantities have a tight correlation, if
assessed over finite time intervals. Figure 1 shows this correlation
for 8 years of recent GOES data, using one-day intervals.

[[File:533_f1.png|center|thumb|600px|caption|Figure 1: 
Variance vs. mean for one-day intervals over 8 years of GOES
soft X-ray (1-8 Å) timeseries, using standard one-minute
sampling.
The diagonal lines show direct proportionality, as would be
expected from
[https://en.wikipedia.org/wiki/Poisson_distribution Poisson statistics].
The X-axis (the means) covers fluxes equivalent to GOES flare classes
AO.1 to X1.
]]

The figure shows clear and systematic deviations from Poisson statistics,
and the correlations fit a power law over the entire dynamic range of
a solar cycle:

var(S) = mean(S)α

where S is the flux and var(S) is its variance. For the 8-year
sample, with no data selection at all, we find α = 3.06 ±. 0.05.
There is no obvious dependence on the solar cycle (Figure 2).

[[File:533f2.png|center|thumb|400px|caption|Figure 1: 
Annual values of the slope parameter α.
]]

The fact that the same power law fits the quiet Sun as well as the flaring Sun suggests
that the flare mechanism is all that one needs to explain.
This result helps to exclude the nanoflare idea for coronal heating (see Ref. [3]).

== Taylor's law ==

This kind of relationship is known as Taylor's law, and I am grateful
to ChatGPT for pointing me to Ref. [2].
It is empirical and describes many natural populations (this Taylor studied
ecology), but also many physical systems and even some distributions of
a purely mathematical nature.
The index α follows the physical origin of the distribution:
α > 1 implies correlations or bunching of events, α = 1 implies random
occurrence, and α < 1 implies the suppression of occurrence by an event.
Interestingly the lowest GOES flux levels (2018 in Figure 1) show a
piling-up at the bottom of the scale with this property, probably produced
by the necessarily finite digital levels at the background detection limit.

== Conclusion ==

This Nugget is based on Ref. [3], and there is just a question about this: do stellar X-ray time series have the same exponent?

== References ==

[1] [http://adsabs.harvard.edu/abs/1991SoPh..133..357H "Solar flares, microflares, nanoflares, and coronal heating"]

[2] [https://ui.adsabs.harvard.edu/abs/1961Natur.189..732T "Aggregation, Variance and the Mean"]

[3] Solar Physics, in review 2026

Electron-Ion equilibration in CME-driven shocks

2026-08-27T14:59:58Z

Hhudson:

{{Infobox Nugget |name = Nugget
|title = Electron-Ion equilibration in CME-driven shocks
|first_author = John RAYMOND
|publish_date = August 3, 2026\
|number = 532
|next_nugget =
|previous_nugget = {{#ask: [[Category:Nugget]] [[RHESSI Nugget Index::531]]}}
}}

== Introduction ==

Coronal mass ejections
[https://en.wikipedia.org/wiki/Coronal_mass_ejection (CMEs)]
drive shock waves into regions of very low collisionality.
The jumps in density, pressure and temperature at a shock wave in dense
gas are mediated by particle collisions, and that leads to thermal
equilibrium: equal temperatures of all particle species and a Maxwellian
velocity distribution for each species.
In a low density plasma,
on the other hand, the collision lengths are large, and the shock
jump must therefore be mediated by electromagnetic fields and plasma waves.
That can lead to non-Maxwellian velocity distributions, such as Solar
Energetic Particles (SEPs), and to differing electron and ion
temperatures.

In the solar wind, postshock electron temperatures are generally
less than proton temperatures (e.g., Ref. [1])
though there is considerable scatter.
Shocks in supernova
remnants reach higher Mach numbers, and they show a trend
of decreasing electron-to-ion temperature ratio with increasing
shock speed or Mach number (Ref. [2]). CME-driven shocks
In the solar corona are more difficult to study, but they are
observed as type II radio bursts and as faint emission in UV, EUV
and white light coronagraph spectra and images (e.g., Ref. [3]).

== How do we infer plasma temperatures? ==

In some cases, it is possible to infer the electron temperature
behind a coronal shock by comparing extreme ultraviolet images from
[https://aia.lmsal.com AIA] in different bands.
When the electrons are suddenly heated in a shock, the iron ions
are successively ionized from Fe X to Fe XII to Fe XIV to Fe XVI
(The AIA 171, 193, 211 and 335 Å bands).
If the density is known from
[https://en.wikipedia.org/wiki/Solar_radio_emission type II]
radio emission or from a global MHD model of the corona, the lags
between the appearance of the shock in the
different bands indicate the electron temperature (Refs. [4,5]).
Figure 1 shows a CME-driven shock observed
on 2010 June 13, with the 3D structure inferred from AIA and STEREO
images (Ref. [5]).
Figure 2 shows the dimensionless
parameter ΔTe at different positions along the shock front,
where ΔTe = 0 corresponds to equal electron and proton
temperatures and ΔTe = 1 corresponds to no electron heating.
The intermediate values seen in Figure 2 show that these 500-700 km/s
shocks heat the electrons about half as efficiently as the ions.

[[File:532f1.png|center|thumb|600px|caption|Figure 1: 
SDO/AIA 193 Å running difference images at three different times of
the 13 June 2010 CME-driven shock wave. The blue line shows the
outline of the geometric model - here, the data were binned by a
factor of 8 to increase the S/N when fitting the model to the data.
The software captures the irregular shape of the shock, accounting
for angle-dependent acceleration. The shock can be identified as
the bright outer ring of the structure, while the erupting prominence
driving the shock is clearly identified as the bright inner ring
structure. Bottom: Corresponding STEREO-A EUVI 195 Å difference
images, with the geometric model plotted in blue. Right: Labeled
reference of different portions of the shock structure.
]]

[[File:532f2.png|center|thumb|600px|caption|Figure 2: 

A schematic map of the shock, with separate regions highlighted in yellow, magenta, and/or cyan
based on the performance of each model based on the time of the
peaks and the intensities of the peaks. Panels showing the combined
color maps use a CMY subtractive color model to accurately reflect
where the data is unable to differentiate between the models. The
color wheel at the top-right serves as an approximate guide, where
the color changes depending on the separation from the loci for
each model. The solid blue hexagon, for instance, represents good
agreement with both ΔTe = 0.5 (cyan) and
ΔTe = 0.25 (magenta) models
where ΔTe = 0 for complete equilibration and 1 for no
equilibration.
]]

== Conclusion ==

Non-equilibrium plasmas probably dominate the Universe, but they are hard to diagnose via remote-sensing
techniques.
A wealth of plasma physics results from Te ≠ Ti and anisotropic distribution functions,
and large-scale shock waves in the solar corona provide an excellent opportunity to study such effects.

== References ==

[1] [https://ui.adsabs.harvard.edu/abs/2013SSRv..178..633G "Electron-Ion Temperature Equilibration in Collisionless Shocks: The Supernova Remnant-Solar Wind Connection"]

[2] [https://ui.adsabs.harvard.edu/abs/2023ApJ...949...50R "Electron-Ion Temperature Ratio in Astrophysical Shocks"]

[3] [http://adsabs.harvard.edu/abs/2004A%26A...413..363M "Coronal transients and metric type II radio bursts. I. Effects of geometry"]

[4] [https://ui.adsabs.harvard.edu/abs/2011ApJ...738..160M "Observations and Interpretation of a Low Coronal Shock Wave Observed in the EUV by the SDO/AIA"]

[5] [https://ui.adsabs.harvard.edu/abs/2025ApJ...989..175T "A 3D Nonequilibrium Ionization Model of a Shock Wave in the Low Corona. I. Extreme-ultraviolet Emission and Inefficient Electron Heating"]

The Variance of Solar X-ray Flux

2026-08-27T14:58:48Z

Hhudson:

{{Infobox Nugget |name = Nugget
|title = Variance of solar X-ray flux
|first_author = Hugh HUDSON
|publish_date = August 17, 2026
|next_nugget =
|previous_nugget = {{#ask: [[Category:Nugget]] [[RHESSI Nugget Index::531]]}}
}}

== Introduction ==

The time series of solar soft X-ray fluxes has been measured almost
continously since the 1970s, famously by the
[https://www.spaceweather.gov/products/goes-x-ray-flux GOES]
satellite series.
We analyze the timeseries from its 1-8 Å photometers from
the modern GOES-R data, covering the years 2017-2025.

The basic tool used in the analysis is the
[https://mathworld.wolfram.com/PowerSpectrum.html power spectrum],
as inspired by Ref. [1] and a great deal of staring at the timeseries.
These show a somewhat subtle property of the data: the RMS fluctuation,
normalized to the median, tends to be smaller for lower flux levels.
This can be seen real-time (currently) at the
[https://www.astro.gla.ac.uk/users/hsh3f/scratch/fai.html FAI]
("flare anticipation index") link, which shows one-hour intervals.
Note that the variance (and RMS) of this time series is undefined
for long intervals because of the flat power-law occurrence
distribution function of
[https://en.wikipedia.org/wiki/Solar_flare flares] (Ref. [2]),
the dominant source of solar X-ray fluctuations.

== Correlation of variance and mean ==

It turns out that these quantities have a tight correlation, if
assessed over finite time intervals. Figure 1 shows this correlation
for 8 years of recent GOES data, using one-day intervals.

[[File:533_f1.png|center|thumb|600px|caption|Figure 1: 
Variance vs. mean for one-day intervals over 8 years of GOES
soft X-ray (1-8 Å) timeseries, using standard one-minute
sampling.
The diagonal lines show direct proportionality, as would be
expected from
[https://en.wikipedia.org/wiki/Poisson_distribution Poisson statistics].
The X-axis (the means) covers fluxes equivalent to GOES flare classes
AO.1 to X1.
]]

The figure shows clear and systematic deviations from Poisson statistics,
and the correlations fit a power law over the entire dynamic range of
a solar cycle:

var(S) = mean(S)α

where S is the flux and var(S) is its variance. For the 8-year
sample, with no data selection at all, we find α = 3.06 ±. 0.05.
There is no obvious dependence on the solar cycle (Figure 2).

[[File:533f2.png|center|thumb|400px|caption|Figure 1: 
Annual values of the slope parameter α.
]]

The fact that the same power law fits the quiet Sun as well as the flaring Sun suggests
that the flare mechanism is all that one needs to explain.
This result helps to exclude the nanoflare idea for coronal heating (see Ref. [3]).

== Taylor's law ==

This kind of relationship is known as Taylor's law, and I am grateful
to ChatGPT for pointing me to Ref. [2].
It is empirical and describes many natural populations (this Taylor studied
ecology), but also many physical systems and even some distributions of
a purely mathematical nature.
The index α follows the physical origin of the distribution:
α > 1 implies correlations or bunching of events, α = 1 implies random
occurrence, and α < 1 implies the suppression of occurrence by an event.
Interestingly the lowest GOES flux levels (2018 in Figure 1) show a
piling-up at the bottom of the scale with this property, probably produced
by the necessarily finite digital levels at the background detection limit.

== Conclusion ==

This Nugget is based on Ref. [3], and there is just a question about this: do stellar X-ray time series have the same exponent?

== References ==

[1] [http://adsabs.harvard.edu/abs/1991SoPh..133..357H "Solar flares, microflares, nanoflares, and coronal heating"]

[2] [https://ui.adsabs.harvard.edu/abs/1961Natur.189..732T "Aggregation, Variance and the Mean"]

[3] Solar Physics, in review 2026

The Variance of Solar X-ray Flux

2026-08-24T16:01:20Z

Hhudson: /* Correlation of variance and mean */

{{Infobox Nugget |name = Nugget
|title = Variance of solar X-ray flux
|first_author = Hugh HUDSON
|publish_date = August 17, 2026
|next_nugget =
|previous_nugget = {{#ask: [[Category:Nugget]] [[RHESSI Nugget Index::532]]}}
}}

== Introduction ==

The time series of solar soft X-ray fluxes has been measured almost
continously since the 1970s, famously by the
[https://www.spaceweather.gov/products/goes-x-ray-flux GOES]
satellite series.
We analyze the timeseries from its 1-8 Å photometers from
the modern GOES-R data, covering the years 2017-2025.

The basic tool used in the analysis is the
[https://mathworld.wolfram.com/PowerSpectrum.html power spectrum],
as inspired by Ref. [1] and a great deal of staring at the timeseries.
These show a somewhat subtle property of the data: the RMS fluctuation,
normalized to the median, tends to be smaller for lower flux levels.
This can be seen real-time (currently) at the
[https://www.astro.gla.ac.uk/users/hsh3f/scratch/fai.html FAI]
("flare anticipation index") link, which shows one-hour intervals.
Note that the variance (and RMS) of this time series is undefined
for long intervals because of the flat power-law occurrence
distribution function of
[https://en.wikipedia.org/wiki/Solar_flare flares] (Ref. [2]),
the dominant source of solar X-ray fluctuations.

== Correlation of variance and mean ==

It turns out that these quantities have a tight correlation, if
assessed over finite time intervals. Figure 1 shows this correlation
for 8 years of recent GOES data, using one-day intervals.

[[File:533_f1.png|center|thumb|600px|caption|Figure 1: 
Variance vs. mean for one-day intervals over 8 years of GOES
soft X-ray (1-8 Å) timeseries, using standard one-minute
sampling.
The diagonal lines show direct proportionality, as would be
expected from
[https://en.wikipedia.org/wiki/Poisson_distribution Poisson statistics].
The X-axis (the means) covers fluxes equivalent to GOES flare classes
AO.1 to X1.
]]

The figure shows clear and systematic deviations from Poisson statistics,
and the correlations fit a power law over the entire dynamic range of
a solar cycle:

var(S) = mean(S)α

where S is the flux and var(S) is its variance. For the 8-year
sample, with no data selection at all, we find α = 3.06 ±. 0.05.
There is no obvious dependence on the solar cycle (Figure 2).

[[File:533f2.png|center|thumb|400px|caption|Figure 1: 
Annual values of the slope parameter α.
]]

The fact that the same power law fits the quiet Sun as well as the flaring Sun suggests
that the flare mechanism is all that one needs to explain.
This result helps to exclude the nanoflare idea for coronal heating (see Ref. [3]).

== Taylor's law ==

This kind of relationship is known as Taylor's law, and I am grateful
to ChatGPT for pointing me to Ref. [2].
It is empirical and describes many natural populations (this Taylor studied
ecology), but also many physical systems and even some distributions of
a purely mathematical nature.
The index α follows the physical origin of the distribution:
α > 1 implies correlations or bunching of events, α = 1 implies random
occurrence, and α < 1 implies the suppression of occurrence by an event.
Interestingly the lowest GOES flux levels (2018 in Figure 1) show a
piling-up at the bottom of the scale with this property, probably produced
by the necessarily finite digital levels at the background detection limit.

== Conclusion ==

This Nugget is based on Ref. [3], and there is just a question about this: do stellar X-ray time series have the same exponent?

== References ==

[1] [http://adsabs.harvard.edu/abs/1991SoPh..133..357H "Solar flares, microflares, nanoflares, and coronal heating"]

[2] [https://ui.adsabs.harvard.edu/abs/1961Natur.189..732T "Aggregation, Variance and the Mean"]

[3] Solar Physics, in review 2026

File:534f3.png

2026-08-22T15:52:41Z

Hhudson:

File:534f2.png

2026-08-22T15:52:23Z

Hhudson:

File:534f1.png

2026-08-22T15:51:58Z

Hhudson:

The Variance of Solar X-ray Flux

2026-08-22T07:36:47Z

Hhudson: /* Taylor's law */

{{Infobox Nugget |name = Nugget
|title = Variance of solar X-ray flux
|first_author = Hugh HUDSON
|publish_date = August 17, 2026
|next_nugget =
|previous_nugget = {{#ask: [[Category:Nugget]] [[RHESSI Nugget Index::532]]}}
}}

== Introduction ==

The time series of solar soft X-ray fluxes has been measured almost
continously since the 1970s, famously by the
[https://www.spaceweather.gov/products/goes-x-ray-flux GOES]
satellite series.
We analyze the timeseries from its 1-8 Å photometers from
the modern GOES-R data, covering the years 2017-2025.

The basic tool used in the analysis is the
[https://mathworld.wolfram.com/PowerSpectrum.html power spectrum],
as inspired by Ref. [1] and a great deal of staring at the timeseries.
These show a somewhat subtle property of the data: the RMS fluctuation,
normalized to the median, tends to be smaller for lower flux levels.
This can be seen real-time (currently) at the
[https://www.astro.gla.ac.uk/users/hsh3f/scratch/fai.html FAI]
("flare anticipation index") link, which shows one-hour intervals.
Note that the variance (and RMS) of this time series is undefined
for long intervals because of the flat power-law occurrence
distribution function of
[https://en.wikipedia.org/wiki/Solar_flare flares] (Ref. [2]),
the dominant source of solar X-ray fluctuations.

== Correlation of variance and mean ==

It turns out that these quantities have a tight correlation, if
assessed over finite time intervals. Figure 1 shows this correlation
for 8 years of recent GOES data, using one-day intervals.

[[File:533_f1.png|center|thumb|600px|caption|Figure 1: 
Variance vs. mean for one-day intervals over 8 years of GOES
soft X-ray (1-8 Å) timeseries, using standard one-minute
sampling.
The diagonal lines show direct proportionality, as would be
expected from
[https://en.wikipedia.org/wiki/Poisson_distribution Poisson statistics].
The X-axis (the means) covers fluxes equivalent to GOES flare classes
AO.1 to X1.
]]

The figure shows clear and systematic deviations from Poisson statistics,
and the correlations fit a power law over the entire dynamic range of
a solar cycle:

var(S) = mean(S)α

where S is the flux and var(S) is its variance. For the entire 8-year
sample, with no data selection at all, we find α = 3.06 ±. 0.05.
There is no obvious dependence on the solar cycle (Figure 2).

[[File:533f2.png|center|thumb|400px|caption|Figure 1: 
Annual values of the slope parameter α.
]]

The fact that the same power law fits the quiet Sun as well as the flaring Sun suggests
that the flare mechanism is all that one needs to explain.
This result helps to exclude the nanoflare idea for coronal heating (see Ref. [3]).

== Taylor's law ==

This kind of relationship is known as Taylor's law, and I am grateful
to ChatGPT for pointing me to Ref. [2].
It is empirical and describes many natural populations (this Taylor studied
ecology), but also many physical systems and even some distributions of
a purely mathematical nature.
The index α follows the physical origin of the distribution:
α > 1 implies correlations or bunching of events, α = 1 implies random
occurrence, and α < 1 implies the suppression of occurrence by an event.
Interestingly the lowest GOES flux levels (2018 in Figure 1) show a
piling-up at the bottom of the scale with this property, probably produced
by the necessarily finite digital levels at the background detection limit.

== Conclusion ==

This Nugget is based on Ref. [3], and there is just a question about this: do stellar X-ray time series have the same exponent?

== References ==

[1] [http://adsabs.harvard.edu/abs/1991SoPh..133..357H "Solar flares, microflares, nanoflares, and coronal heating"]

[2] [https://ui.adsabs.harvard.edu/abs/1961Natur.189..732T "Aggregation, Variance and the Mean"]

[3] Solar Physics, in review 2026

The Variance of Solar X-ray Flux

2026-08-21T20:27:33Z

Hhudson: /* Correlation of variance and mean */

{{Infobox Nugget |name = Nugget
|title = Variance of solar X-ray flux
|first_author = Hugh HUDSON
|publish_date = August 17, 2026
|next_nugget =
|previous_nugget = {{#ask: [[Category:Nugget]] [[RHESSI Nugget Index::532]]}}
}}

== Introduction ==

The time series of solar soft X-ray fluxes has been measured almost
continously since the 1970s, famously by the
[https://www.spaceweather.gov/products/goes-x-ray-flux GOES]
satellite series.
We analyze the timeseries from its 1-8 Å photometers from
the modern GOES-R data, covering the years 2017-2025.

The basic tool used in the analysis is the
[https://mathworld.wolfram.com/PowerSpectrum.html power spectrum],
as inspired by Ref. [1] and a great deal of staring at the timeseries.
These show a somewhat subtle property of the data: the RMS fluctuation,
normalized to the median, tends to be smaller for lower flux levels.
This can be seen real-time (currently) at the
[https://www.astro.gla.ac.uk/users/hsh3f/scratch/fai.html FAI]
("flare anticipation index") link, which shows one-hour intervals.
Note that the variance (and RMS) of this time series is undefined
for long intervals because of the flat power-law occurrence
distribution function of
[https://en.wikipedia.org/wiki/Solar_flare flares] (Ref. [2]),
the dominant source of solar X-ray fluctuations.

== Correlation of variance and mean ==

It turns out that these quantities have a tight correlation, if
assessed over finite time intervals. Figure 1 shows this correlation
for 8 years of recent GOES data, using one-day intervals.

[[File:533_f1.png|center|thumb|600px|caption|Figure 1: 
Variance vs. mean for one-day intervals over 8 years of GOES
soft X-ray (1-8 Å) timeseries, using standard one-minute
sampling.
The diagonal lines show direct proportionality, as would be
expected from
[https://en.wikipedia.org/wiki/Poisson_distribution Poisson statistics].
The X-axis (the means) covers fluxes equivalent to GOES flare classes
AO.1 to X1.
]]

The figure shows clear and systematic deviations from Poisson statistics,
and the correlations fit a power law over the entire dynamic range of
a solar cycle:

var(S) = mean(S)α

where S is the flux and var(S) is its variance. For the entire 8-year
sample, with no data selection at all, we find α = 3.06 ±. 0.05.
There is no obvious dependence on the solar cycle (Figure 2).

[[File:533f2.png|center|thumb|400px|caption|Figure 1: 
Annual values of the slope parameter α.
]]

The fact that the same power law fits the quiet Sun as well as the flaring Sun suggests
that the flare mechanism is all that one needs to explain.
This result helps to exclude the nanoflare idea for coronal heating (see Ref. [3]).

== Taylor's law ==

This kind of relationship is known as Taylor's law, and I am grateful
to ChatGPT for pointing me to Ref. [2].
It is empirical and describes many natural populations (this Taylor studied
ecology), but also many physical systems and even some distributions of
a purely mathematical nature.
The index α follows the physical nature of the distribution:
α > 1 implies correlations or bunching of events, α = 1 random
occurrence, and α < 1 the suppression of occurrence by an event.
Interestingly the lowest GOES flux levels (2018 in Figure 1) show a
piling-up at the bottom of the scale with this property, probably produced
by finite digital levels.

== Conclusion ==

This Nugget is based on Ref. [3], and there is just a question about this: do stellar X-ray time series have the same exponent?

== References ==

[1] [http://adsabs.harvard.edu/abs/1991SoPh..133..357H "Solar flares, microflares, nanoflares, and coronal heating"]

[2] [https://ui.adsabs.harvard.edu/abs/1961Natur.189..732T "Aggregation, Variance and the Mean"]

[3] Solar Physics, in review 2026

The Variance of Solar X-ray Flux

2026-08-21T20:03:29Z

Hhudson: /* Correlation of variance and mean */

{{Infobox Nugget |name = Nugget
|title = Variance of solar X-ray flux
|first_author = Hugh HUDSON
|publish_date = August 17, 2026
|next_nugget =
|previous_nugget = {{#ask: [[Category:Nugget]] [[RHESSI Nugget Index::532]]}}
}}

== Introduction ==

The time series of solar soft X-ray fluxes has been measured almost
continously since the 1970s, famously by the
[https://www.spaceweather.gov/products/goes-x-ray-flux GOES]
satellite series.
We analyze the timeseries from its 1-8 Å photometers from
the modern GOES-R data, covering the years 2017-2025.

The basic tool used in the analysis is the
[https://mathworld.wolfram.com/PowerSpectrum.html power spectrum],
as inspired by Ref. [1] and a great deal of staring at the timeseries.
These show a somewhat subtle property of the data: the RMS fluctuation,
normalized to the median, tends to be smaller for lower flux levels.
This can be seen real-time (currently) at the
[https://www.astro.gla.ac.uk/users/hsh3f/scratch/fai.html FAI]
("flare anticipation index") link, which shows one-hour intervals.
Note that the variance (and RMS) of this time series is undefined
for long intervals because of the flat power-law occurrence
distribution function of
[https://en.wikipedia.org/wiki/Solar_flare flares] (Ref. [2]),
the dominant source of solar X-ray fluctuations.

== Correlation of variance and mean ==

It turns out that these quantities have a tight correlation, if
assessed over finite time intervals. Figure 1 shows this correlation
for 8 years of recent GOES data, using one-day intervals.

[[File:533_f1.png|center|thumb|600px|caption|Figure 1: 
Variance vs. mean for one-day intervals over 8 years of GOES
soft X-ray (1-8 Å) timeseries, using standard one-minute
sampling.
The diagonal lines show direct proportionality, as would be
expected from
[https://en.wikipedia.org/wiki/Poisson_distribution Poisson statistics].
]]

The figure shows clear and systematic deviations from Poisson statistics,
and the correlations fit a power law over the entire dynamic range of
a solar cycle:

var(S) = mean(S)α

where S is the flux and var(S) is its variance. For the entire 8-year
sample, with no data selection at all, we find α = 3.06 ±. 0.05.
There is no obvious dependence on the solar cycle (Figure 2).

[[File:533f2.png|center|thumb|400px|caption|Figure 1: 
Annual values of the slope parameter α.
]]

The fact that the same power law fits the quiet Sun as well as the flaring Sun suggests
that the flare mechanism is all that one needs to explain.
This result helps to exclude the nanoflare idea for coronal heating (see Ref. [3]).

== Taylor's law ==

This kind of relationship is known as Taylor's law, and I am grateful
to ChatGPT for pointing me to Ref. [2].
It is empirical and describes many natural populations (this Taylor studied
ecology), but also many physical systems and even some distributions of
a purely mathematical nature.
The index α follows the physical nature of the distribution:
α > 1 implies correlations or bunching of events, α = 1 random
occurrence, and α < 1 the suppression of occurrence by an event.
Interestingly the lowest GOES flux levels (2018 in Figure 1) show a
piling-up at the bottom of the scale with this property, probably produced
by finite digital levels.

== Conclusion ==

This Nugget is based on Ref. [3], and there is just a question about this: do stellar X-ray time series have the same exponent?

== References ==

[1] [http://adsabs.harvard.edu/abs/1991SoPh..133..357H "Solar flares, microflares, nanoflares, and coronal heating"]

[2] [https://ui.adsabs.harvard.edu/abs/1961Natur.189..732T "Aggregation, Variance and the Mean"]

[3] Solar Physics, in review 2026

SolarNuggets

2026-08-21T19:59:42Z

Hhudson: Added No. 533

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 = The Variance of Solar X-ray Flux
|number = 533
|first_author = Hugh HUDSON
|publish_date = 17 August 2026
|description = Taylor's law describes solar X-ray variability all the way
|image=Icon533.png}}

{{Nugget Badge
|title = Electron-Ion equilibration in CME-driven shocks
|number = 532
|first_author = John RAYMOND
|publish_date = 3 August 2026
|description = Signatures of heliospheric plasmas not in thermal equilibrium
|image=Icon532.png}}

{{Nugget Badge
|title = The Source Surface Height Through the Solar Cycle: A Path to Better Solar Wind Forecasts
|number = 531
|first_author = Sandeep KUMAR
|second_author = and Nandita SRIVASTAVA
||publish_date = 20 July 2026
|description = Following the solar cycle with optimized PFSS modeling
|image=Icon531.png}}

{{Nugget Badge
|title = Filament Eruptions as seen in the Sun-as-a-star H-alpha Spectrum
|number = 530
|first_author = Junyi ZHANG
|second_author = and Yijun HOU
||publish_date = 6 July 2026
|description = H-alpha from a space platform shows Sun-as-a-star signatures of ejecta
|image=Icon530.png}}

{{Nugget Badge
|title = Particle Pressure and CMEs
|number = 529
|first_author = Hugh HUDSON
|second_author = and Ed CLIVER
||publish_date = 22 June 2026
|description = High-energy particles can exert substantial pressure and affect eruption dynamics
|image=Icon529.png}}

{{Nugget Badge
|title = White-Light and Lyman-alpha Emissions in Solar Flares: Timing, Timescale, Energy, and Scaling‎‎
|number = 528
|first_author = Dechao SONG
||publish_date = 8 June 2026
|description = A new catalog of white-light flares including novel Lyman-alpha data
|image=Icon528.png}}

{{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:Icon533.png

2026-08-21T19:58:53Z

Hhudson:

The Variance of Solar X-ray Flux

2026-08-21T19:46:14Z

Hhudson: /* Correlation of variance and mean */

{{Infobox Nugget |name = Nugget
|title = Variance of solar X-ray flux
|first_author = Hugh HUDSON
|publish_date = August 17, 2026
|next_nugget =
|previous_nugget = {{#ask: [[Category:Nugget]] [[RHESSI Nugget Index::532]]}}
}}

== Introduction ==

The time series of solar soft X-ray fluxes has been measured almost
continously since the 1970s, famously by the
[https://www.spaceweather.gov/products/goes-x-ray-flux GOES]
satellite series.
We analyze the timeseries from its 1-8 Å photometers from
the modern GOES-R data, covering the years 2017-2025.

The basic tool used in the analysis is the
[https://mathworld.wolfram.com/PowerSpectrum.html power spectrum],
as inspired by Ref. [1] and a great deal of staring at the timeseries.
These show a somewhat subtle property of the data: the RMS fluctuation,
normalized to the median, tends to be smaller for lower flux levels.
This can be seen real-time (currently) at the
[https://www.astro.gla.ac.uk/users/hsh3f/scratch/fai.html FAI]
("flare anticipation index") link, which shows one-hour intervals.
Note that the variance (and RMS) of this time series is undefined
for long intervals because of the flat power-law occurrence
distribution function of
[https://en.wikipedia.org/wiki/Solar_flare flares] (Ref. [2]),
the dominant source of solar X-ray fluctuations.

== Correlation of variance and mean ==

It turns out that these quantities have a tight correlation, if
assessed over finite time intervals. Figure 1 shows this correlation
for 8 years of recent GOES data, using one-day intervals.

[[File:533_f1.png|center|thumb|600px|caption|Figure 1: 
Variance vs. mean for one-day intervals over 8 years of GOES
soft X-ray (1-8 Å) timeseries, using standard one-minute
sampling.
The diagonal lines show direct proportionality, as would be
expected from
[https://en.wikipedia.org/wiki/Poisson_distribution Poisson statistics].
]]

The figure shows clear and systematic deviations from Poisson statistics,
and the correlations fit a power law over the entire dynamic range of
a solar cycle:

var(S) = mean(S)α

where S is the flux and var(S) is its variance. For the entire 8-year
sample, with no data selection at all, we find α = 3.06 ±. 0.05.
There is no obvious dependence on the solar cycle (Figure 2).

[[File:533f2.png|center|thumb|400px|caption|Figure 1: 
Annual values of the slope parameter α.
]]

== Taylor's law ==

This kind of relationship is known as Taylor's law, and I am grateful
to ChatGPT for pointing me to Ref. [2].
It is empirical and describes many natural populations (this Taylor studied
ecology), but also many physical systems and even some distributions of
a purely mathematical nature.
The index α follows the physical nature of the distribution:
α > 1 implies correlations or bunching of events, α = 1 random
occurrence, and α < 1 the suppression of occurrence by an event.
Interestingly the lowest GOES flux levels (2018 in Figure 1) show a
piling-up at the bottom of the scale with this property, probably produced
by finite digital levels.

== Conclusion ==

This Nugget is based on Ref. [3], and there is just a question about this: do stellar X-ray time series have the same exponent?

== References ==

[1] [http://adsabs.harvard.edu/abs/1991SoPh..133..357H "Solar flares, microflares, nanoflares, and coronal heating"]

[2] [https://ui.adsabs.harvard.edu/abs/1961Natur.189..732T "Aggregation, Variance and the Mean"]

[3] Solar Physics, in review 2026

File:533f2.png

2026-08-21T19:45:51Z

Hhudson:

The Variance of Solar X-ray Flux

2026-08-21T19:45:25Z

Hhudson: /* Correlation of variance and mean */

{{Infobox Nugget |name = Nugget
|title = Variance of solar X-ray flux
|first_author = Hugh HUDSON
|publish_date = August 17, 2026
|next_nugget =
|previous_nugget = {{#ask: [[Category:Nugget]] [[RHESSI Nugget Index::532]]}}
}}

== Introduction ==

The time series of solar soft X-ray fluxes has been measured almost
continously since the 1970s, famously by the
[https://www.spaceweather.gov/products/goes-x-ray-flux GOES]
satellite series.
We analyze the timeseries from its 1-8 Å photometers from
the modern GOES-R data, covering the years 2017-2025.

The basic tool used in the analysis is the
[https://mathworld.wolfram.com/PowerSpectrum.html power spectrum],
as inspired by Ref. [1] and a great deal of staring at the timeseries.
These show a somewhat subtle property of the data: the RMS fluctuation,
normalized to the median, tends to be smaller for lower flux levels.
This can be seen real-time (currently) at the
[https://www.astro.gla.ac.uk/users/hsh3f/scratch/fai.html FAI]
("flare anticipation index") link, which shows one-hour intervals.
Note that the variance (and RMS) of this time series is undefined
for long intervals because of the flat power-law occurrence
distribution function of
[https://en.wikipedia.org/wiki/Solar_flare flares] (Ref. [2]),
the dominant source of solar X-ray fluctuations.

== Correlation of variance and mean ==

It turns out that these quantities have a tight correlation, if
assessed over finite time intervals. Figure 1 shows this correlation
for 8 years of recent GOES data, using one-day intervals.

[[File:533_f1.png|center|thumb|600px|caption|Figure 1: 
Variance vs. mean for one-day intervals over 8 years of GOES
soft X-ray (1-8 Å) timeseries, using standard one-minute
sampling.
The diagonal lines show direct proportionality, as would be
expected from
[https://en.wikipedia.org/wiki/Poisson_distribution Poisson statistics].
]]

The figure shows clear and systematic deviations from Poisson statistics,
and the correlations fit a power law over the entire dynamic range of
a solar cycle:

var(S) = mean(S)α

where S is the flux and var(S) is its variance. For the entire 8-year
sample, with no data selection at all, we find α = 3.06 ±. 0.05.
There is no obvious dependence on the solar cycle (Figure 2).

[[File:533f2.png|center|thumb|600px|caption|Figure 1: 
Annual values of the slope parameter α.
]]

== Taylor's law ==

This kind of relationship is known as Taylor's law, and I am grateful
to ChatGPT for pointing me to Ref. [2].
It is empirical and describes many natural populations (this Taylor studied
ecology), but also many physical systems and even some distributions of
a purely mathematical nature.
The index α follows the physical nature of the distribution:
α > 1 implies correlations or bunching of events, α = 1 random
occurrence, and α < 1 the suppression of occurrence by an event.
Interestingly the lowest GOES flux levels (2018 in Figure 1) show a
piling-up at the bottom of the scale with this property, probably produced
by finite digital levels.

== Conclusion ==

This Nugget is based on Ref. [3], and there is just a question about this: do stellar X-ray time series have the same exponent?

== References ==

[1] [http://adsabs.harvard.edu/abs/1991SoPh..133..357H "Solar flares, microflares, nanoflares, and coronal heating"]

[2] [https://ui.adsabs.harvard.edu/abs/1961Natur.189..732T "Aggregation, Variance and the Mean"]

[3] Solar Physics, in review 2026

The Variance of Solar X-ray Flux

2026-08-21T19:40:43Z

Hhudson: /* Introduction */

{{Infobox Nugget |name = Nugget
|title = Variance of solar X-ray flux
|first_author = Hugh HUDSON
|publish_date = August 17, 2026
|next_nugget =
|previous_nugget = {{#ask: [[Category:Nugget]] [[RHESSI Nugget Index::532]]}}
}}

== Introduction ==

The time series of solar soft X-ray fluxes has been measured almost
continously since the 1970s, famously by the
[https://www.spaceweather.gov/products/goes-x-ray-flux GOES]
satellite series.
We analyze the timeseries from its 1-8 Å photometers from
the modern GOES-R data, covering the years 2017-2025.

The basic tool used in the analysis is the
[https://mathworld.wolfram.com/PowerSpectrum.html power spectrum],
as inspired by Ref. [1] and a great deal of staring at the timeseries.
These show a somewhat subtle property of the data: the RMS fluctuation,
normalized to the median, tends to be smaller for lower flux levels.
This can be seen real-time (currently) at the
[https://www.astro.gla.ac.uk/users/hsh3f/scratch/fai.html FAI]
("flare anticipation index") link, which shows one-hour intervals.
Note that the variance (and RMS) of this time series is undefined
for long intervals because of the flat power-law occurrence
distribution function of
[https://en.wikipedia.org/wiki/Solar_flare flares] (Ref. [2]),
the dominant source of solar X-ray fluctuations.

== Correlation of variance and mean ==

It turns out that these quantities have a tight correlation, if
assessed over finite time intervals. Figure 1 shows this correlation
for 8 years of recent GOES data, using one-day intervals.

[[File:533_f1.png|center|thumb|600px|caption|Figure 1: 
Variance vs. mean for one-day intervals over 8 years of GOES
soft X-ray (1-8 Å) timeseries, using standard one-minute
sampling.
The diagonal lines show direct proportionality, as would be
expected from
[https://en.wikipedia.org/wiki/Poisson_distribution Poisson statistics].
]]

The figure shows clear and systematic deviations from Poisson statistics,
and the correlations fit a power law over the entire dynamic range of
a solar cycle:

var(S) = mean(S)α

where S is the flux and var(S) is its variance. For the entire 8-year
sample, with no data selection at all, we find α = 3.06 ±. 0.05.

== Taylor's law ==

This kind of relationship is known as Taylor's law, and I am grateful
to ChatGPT for pointing me to Ref. [2].
It is empirical and describes many natural populations (this Taylor studied
ecology), but also many physical systems and even some distributions of
a purely mathematical nature.
The index α follows the physical nature of the distribution:
α > 1 implies correlations or bunching of events, α = 1 random
occurrence, and α < 1 the suppression of occurrence by an event.
Interestingly the lowest GOES flux levels (2018 in Figure 1) show a
piling-up at the bottom of the scale with this property, probably produced
by finite digital levels.

== Conclusion ==

This Nugget is based on Ref. [3], and there is just a question about this: do stellar X-ray time series have the same exponent?

== References ==

[1] [http://adsabs.harvard.edu/abs/1991SoPh..133..357H "Solar flares, microflares, nanoflares, and coronal heating"]

[2] [https://ui.adsabs.harvard.edu/abs/1961Natur.189..732T "Aggregation, Variance and the Mean"]

[3] Solar Physics, in review 2026

The Variance of Solar X-ray Flux

2026-08-21T19:38:19Z

Hhudson:

{{Infobox Nugget |name = Nugget
|title = Variance of solar X-ray flux
|first_author = Hugh HUDSON
|publish_date = August 17, 2026
|next_nugget =
|previous_nugget = {{#ask: [[Category:Nugget]] [[RHESSI Nugget Index::532]]}}
}}

== Introduction ==

The time series of solar soft X-ray fluxes has been measured almost
continously since the 1970s, famously by the
[https://www.spaceweather.gov/products/goes-x-ray-flux GOES]
satellite series.
We analyze the timeseries from its 1-8 Å photometers from
the modern GOES-R data, covering the years 2017-2025.

The basic tool used in the analysis is the power spectrum,
as inspired by Ref. [1] and a great deal of staring at the timeseries.
These show a somewhat subtle property of the data: the RMS fluctuation,
normalized to the median, tends to be smaller for lower flux levels.
This can be seen real-time (currently) at the
[https://www.astro.gla.ac.uk/users/hsh3f/scratch/fai.html FAI]
("flare anticipation index") link, which shows one-hour intervals.
Note that the variance (and RMS) of this time series is undefined
for long intervals because of the flat power-law occurrence
distribution function of
[https://en.wikipedia.org/wiki/Solar_flare flares] (Ref. [2]),
the dominant source of solar X-ray fluctuations.

== Correlation of variance and mean ==

It turns out that these quantities have a tight correlation, if
assessed over finite time intervals. Figure 1 shows this correlation
for 8 years of recent GOES data, using one-day intervals.

[[File:533_f1.png|center|thumb|600px|caption|Figure 1: 
Variance vs. mean for one-day intervals over 8 years of GOES
soft X-ray (1-8 Å) timeseries, using standard one-minute
sampling.
The diagonal lines show direct proportionality, as would be
expected from
[https://en.wikipedia.org/wiki/Poisson_distribution Poisson statistics].
]]

The figure shows clear and systematic deviations from Poisson statistics,
and the correlations fit a power law over the entire dynamic range of
a solar cycle:

var(S) = mean(S)α

where S is the flux and var(S) is its variance. For the entire 8-year
sample, with no data selection at all, we find α = 3.06 ±. 0.05.

== Taylor's law ==

This kind of relationship is known as Taylor's law, and I am grateful
to ChatGPT for pointing me to Ref. [2].
It is empirical and describes many natural populations (this Taylor studied
ecology), but also many physical systems and even some distributions of
a purely mathematical nature.
The index α follows the physical nature of the distribution:
α > 1 implies correlations or bunching of events, α = 1 random
occurrence, and α < 1 the suppression of occurrence by an event.
Interestingly the lowest GOES flux levels (2018 in Figure 1) show a
piling-up at the bottom of the scale with this property, probably produced
by finite digital levels.

== Conclusion ==

This Nugget is based on Ref. [3], and there is just a question about this: do stellar X-ray time series have the same exponent?

== References ==

[1] [http://adsabs.harvard.edu/abs/1991SoPh..133..357H "Solar flares, microflares, nanoflares, and coronal heating"]

[2] [https://ui.adsabs.harvard.edu/abs/1961Natur.189..732T "Aggregation, Variance and the Mean"]

[3] Solar Physics, in review 2026

File:533f1.png

2026-08-21T19:34:36Z

Hhudson:

The Variance of Solar X-ray Flux

2026-08-21T19:31:28Z

Hhudson: No. 533 initial upload

{{Infobox Nugget |name = Nugget
|title = Variance of solar X-ray flux
|first_author = Hugh HUDSON
|publish_date = August 17, 2026
|next_nugget =
|previous_nugget = {{#ask: [[Category:Nugget]] [[RHESSI Nugget Index::532]]}}
}}

== Introduction ==

The time series of solar soft X-ray fluxes has been measured almost
continously since the 1970s, famously by the
[https://www.spaceweather.gov/products/goes-x-ray-flux GOES]
satellite series.
We analyze the timeseries from its 1-8 Å photometers from
the modern GOES-R data, covering the years 2017-2025.

The basic tool used in the analysis is the power spectrum,
as inspired by Ref. [1] and a great deal of staring at the timeseries.
These show a somewhat subtle property of the data: the RMS fluctuation,
normalized to the median, tends to be smaller for lower flux levels.
This can be seen real-time (currently) at the
[https://www.astro.gla.ac.uk/users/hsh3f/scratch/fai.html FAI]
("flare anticipation index") link, which shows one-hour intervals.
Note that the variance (and RMS) of this time series is undefined
for long intervals because of the flat power-law occurrence
distribution function of
[https://en.wikipedia.org/wiki/Solar_flare flares] (Ref. [2]),
the dominant source of solar X-ray fluctuations.

== Correlation of variance and mean ==

It turns out that these quantities have a tight correlation, if
assessed over finite time intervals. Figure 1 shows this correlation
for 8 years of recent GOES data, using one-day intervals.

[[File:533f1.png|center|thumb|800px|caption|Figure 1: 
Variance vs. mean for one-day intervals over 8 years of GOES
soft X-ray (1-8 Å) timeseries, using standard one-minute
sampling.
The diagonal lines show direct proportionality, as would be
expected from
[https://en.wikipedia.org/wiki/Poisson_distribution Poisson statistics].
]]

The figure shows clear and systematic deviations from Poisson statistics,
and the correlations fit a power law over the entire dynamic range of
a solar cycle:

var(S) = mean(S)α

where S is the flux and var(S) is its variance. For the entire 8-year
sample, with no data selection at all, we find α = 3.06 ±. 0.05.

== Taylor's law ==

This kind of relationship is known as Taylor's law, and I am grateful
to ChatGPT for pointing me to Ref. [2].
It is empirical and describes many natural populations (this Taylor studied
ecology), but also many physical systems and even some distributions of
a purely mathematical nature.
The index α follows the physical nature of the distribution:
α > 1 implies correlations or bunching of events, α = 1 random
occurrence, and α < 1 the suppression of occurrence by an event.
Interestingly the lowest GOES flux levels (2018 in Figure 1) show a
piling-up at the bottom of the scale with this property, probably produced
by finite digital levels.

== Conclusion ==

Just a question: do stellar X-ray time series have the same exponent?

== References ==

[1] [http://adsabs.harvard.edu/abs/1991SoPh..133..357H "Solar flares, microflares, nanoflares, and coronal heating"]

[2] [https://ui.adsabs.harvard.edu/abs/1961Natur.189..732T "Aggregation, Variance and the Mean"]

File:533 f1.png

2026-08-21T19:28:41Z

Hhudson:

SolarNuggets

2026-08-05T19:38:57Z

Hhudson: Added 531 and 532

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).

Filament Eruptions as seen in the Sun-as-a-star H-alpha Spectrum

{{Nugget Badge
|title = Electron-Ion equilibration in CME-driven shocks
|number = 532
|first_author = John RAYMOND
|publish_date = 3 August 2026
|description = Signatures of heliospheric plasmas not in thermal equilibrium
|image=Icon532.png}}

{{Nugget Badge
|title = The Source Surface Height Through the Solar Cycle: A Path to Better Solar Wind Forecasts
|number = 531
|first_author = Sandeep KUMAR
|second_author = and Nandita SRIVASTAVA
||publish_date = 20 July 2026
|description = Following the solar cycle with optimized PFSS modeling
|image=Icon531.png}}

{{Nugget Badge
|title = Filament Eruptions as seen in the Sun-as-a-star H-alpha Spectrum
|number = 530
|first_author = Junyi ZHANG
|second_author = and Yijun HOU
||publish_date = 6 July 2026
|description = H-alpha from a space platform shows Sun-as-a-star signatures of ejecta
|image=Icon530.png}}

{{Nugget Badge
|title = Particle Pressure and CMEs
|number = 529
|first_author = Hugh HUDSON
|second_author = and Ed CLIVER
||publish_date = 22 June 2026
|description = High-energy particles can exert substantial pressure and affect eruption dynamics
|image=Icon529.png}}

{{Nugget Badge
|title = White-Light and Lyman-alpha Emissions in Solar Flares: Timing, Timescale, Energy, and Scaling‎‎
|number = 528
|first_author = Dechao SONG
||publish_date = 8 June 2026
|description = A new catalog of white-light flares including novel Lyman-alpha data
|image=Icon528.png}}

{{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:Icon531.png

2026-08-05T19:32:59Z

Hhudson:

File:Icon532.png

2026-08-05T19:32:32Z

Hhudson:

The Source Surface Height Through the Solar Cycle: A Path to Better Solar Wind Forecasts

2026-08-05T12:59:15Z

Hhudson: Author's fixes

{{Infobox Nugget |name = Nugget
|title = The Source Surface Height Through the Solar Cycle: A Path to Better Solar Wind Forecasts
|number = 531
|first_author = Sandeep KUMAR
|second_author = Nandita SRIVASTAVA
|publish_date = July 20, 2026
|next_nugget =
|previous_nugget = {{#ask: [[Category:Nugget]] [[RHESSI Nugget Index::530]]}}
}}

== Introduction ==

The potential field source surface (PFSS) model serves as the basis
of many state-of-the-art space weather forecasting frameworks,
as described in our Ref. [1].
Essentially PFSS takes the photospheric magnetic field, observable
in detail by [https://en.wikipedia.org/wiki/Zeeman_effect Zeeman effect]
spectroscopy, and uses it to extrapolate into the solar corona.
This requires the assumption of just a single parameter: the radial
distance of the "source surface", a fictitious sphere separating
radial field of the solar wind, from the structured field of the photosphere.
Mathematically any field induced by external sources can be represented by a
fitting
[https://en.wikipedia.org/wiki/Potential_theory spherical harmonic]
functions at its boundaries.
This is tractable but physically it may seem terribly wrong,
since it ignores all coronal field sources (currents) within the volume itself.
But it works surprisingly well, perhaps because the currents that we
know to be present only make a minor perturbation of the basic potential
field.

== The nature of the source surface ==

The PFSS model contains only a single free parameter, the source surface
height, at which magnetic field lines are assumed to be exactly radial.
A value of 2.5 R⊙ for the source-surface height has
traditionally been adopted in most studies.
Optimizing the source-surface value significantly improves model forecasts
of the solar-wind speed as observed at the L1
[https://science.nasa.gov/solar-system/resources/faq/what-are-lagrange-points/ Lagrangian point],
just upstream of Earth in the
[https://en.wikipedia.org/wiki/Solar_wind solar wind] (Ref. [1]).
This study employed two types ("HU STD" and "HU ZPC"] of
([https://en.wikipedia.org/wiki/Global_Oscillations_Network_Group GONG)
synoptic magnetic field maps.
The fidelity of these data
was confirmed by comparing the extrapolated global
magnetic field structures with the large-scale corona observed in
the extended field of view of the PROBA2/SWAP images as shown in
Figure 1.

[[File:531f1.png|center|thumb|600px|caption|Figure 1: 
PFSS-extrapolated magnetic field lines overlaid on the
[https://www.cosmos.esa.int/web/proba-2/swap SWAP]
(top and bottom panel) image of 20 August 2017, 10:45 UT. The middle
panel shows the SWAP mosaic without PFSS extrapolation. The top
left panel shows PFSS extrapolation with HU STD map, and the bottom
left panel with HU ZPC map (on 20 August 2017, 12:14 UT). The right
column shows the zoomed-in version of the white rectangle on the
left panels.
]]

== The solar cycle ==

How must the PFSS model evolve through the
[https://www.spaceweather.gov/products/solar-cycle-progression solar cycle],
during which the solar wind obviously changes substantially?
In Ref. [3] we carried out one of the most comprehensive and
long-term studies of
SS height optimisation for solar wind prediction at L1, analyzing
synoptic magnetograms from both space-based
([http://hmi.stanford.edu SDO/HMI]) and ground-based
([https://gong.nso.edu GONG]) observatories, across nearly three solar cycles, SC23-SC25.
This optimization used the PFSS parameters in the model of Ref. [2] to
compare with the wind-speed observations.
Our main finding is that the optimal SS height varies systematically
with the solar cycle: higher SS heights (≥2.5 R⊙) provide better
solar wind speed predictions during solar minimum, whereas lower
SS heights (<2.5 R⊙) perform better during solar maximum, suggesting
a relationship between SS height and SC phase over long timescales.
We also found that the optimized SS height depends on the choice
of magnetogram, whereas the pattern remains similar for a given
choice of magnetograms. The HMI and GONG "ZPC" magnetograms perform
similarly, and both provide better forecasting than GONG "STD" maps,
as shown in Figure 2. The results provide strong evidence
that solar-cycle-dependent optimization of the PFSS source surface
height is a practical way to improve solar wind forecasting, which
serves as the foundation for heliospheric models.

[[File:531f2.png|center|thumb|600px|caption|Figure 2: 
Top panel: the source-surface radial height, in black for the standard
fixed value of 2.5 R⊙ and in blue and gold for two
alternative optimizations.
The time range covers the 100
[https://en.wikipedia.org/wiki/Solar_rotation Carrington rotations]
from January 2018 (solar minimum) to July 2025 (high activity).
The lower panel shows Pearson correlation coefficients for predictions of
the solar-wind speed.
]]

== Conclusions ==

Our adjusted PFSS radii clearly improve forecasts of the solar-wind speed.
The study highlights an inherent limitation of the PFSS model, which assumes a spherical source surface.
This simplifying assumption restricts further improvement in the correlation coefficient.
We anticipate much greater improvements from future modeling frameworks outside that of spherical symmetry of the source surface.

== References ==

[1] [https://ui.adsabs.harvard.edu/abs/2025JSWSC..15...24K "On the role of source surface height and magnetograms in solar wind forecast accuracy"]

[2] [http://adsabs.harvard.edu/abs/2015SpWea..13..154R "On the role played by magnetic expansion factor in the prediction of solar wind speed"]

[3] [https://ui.adsabs.harvard.edu/abs/2026ApJ..1006...26K "Source Surface Height Optimization for Improved Solar Wind Velocity Forecasting across Solar Cycles 23, 24, and 25"]

Electron-Ion equilibration in CME-driven shocks

2026-08-05T08:19:08Z

Hhudson: /* Conclusion */

{{Infobox Nugget |name = Nugget
|title = Electron-Ion equilibration in CME-driven shocks
|first_author = John RAYMOND
|publish_date = August 3, 2026
|next_nugget =
|previous_nugget = {{#ask: [[Category:Nugget]] [[RHESSI Nugget Index::531]]}}
}}

== Introduction ==

Coronal mass ejections
[https://en.wikipedia.org/wiki/Coronal_mass_ejection (CMEs)]
drive shock waves into regions of very low collisionality.
The jumps in density, pressure and temperature at a shock wave in dense
gas are mediated by particle collisions, and that leads to thermal
equilibrium: equal temperatures of all particle species and a Maxwellian
velocity distribution for each species.
In a low density plasma,
on the other hand, the collision lengths are large, and the shock
jump must therefore be mediated by electromagnetic fields and plasma waves.
That can lead to non-Maxwellian velocity distributions, such as Solar
Energetic Particles (SEPs), and to differing electron and ion
temperatures.

In the solar wind, postshock electron temperatures are generally
less than proton temperatures (e.g., Ref. [1])
though there is considerable scatter.
Shocks in supernova
remnants reach higher Mach numbers, and they show a trend
of decreasing electron-to-ion temperature ratio with increasing
shock speed or Mach number (Ref. [2]). CME-driven shocks
In the solar corona are more difficult to study, but they are
observed as type II radio bursts and as faint emission in UV, EUV
and white light coronagraph spectra and images (e.g., Ref. [3]).

== How do we infer plasma temperatures? ==

In some cases, it is possible to infer the electron temperature
behind a coronal shock by comparing extreme ultraviolet images from
[https://aia.lmsal.com AIA] in different bands.
When the electrons are suddenly heated in a shock, the iron ions
are successively ionized from Fe X to Fe XII to Fe XIV to Fe XVI
(The AIA 171, 193, 211 and 335 Å bands).
If the density is known from
[https://en.wikipedia.org/wiki/Solar_radio_emission type II]
radio emission or from a global MHD model of the corona, the lags
between the appearance of the shock in the
different bands indicate the electron temperature (Refs. [4,5]).
Figure 1 shows a CME-driven shock observed
on 2010 June 13, with the 3D structure inferred from AIA and STEREO
images (Ref. [5]).
Figure 2 shows the dimensionless
parameter ΔTe at different positions along the shock front,
where ΔTe = 0 corresponds to equal electron and proton
temperatures and ΔTe = 1 corresponds to no electron heating.
The intermediate values seen in Figure 2 show that these 500-700 km/s
shocks heat the electrons about half as efficiently as the ions.

[[File:532f1.png|center|thumb|600px|caption|Figure 1: 
SDO/AIA 193 Å running difference images at three different times of
the 13 June 2010 CME-driven shock wave. The blue line shows the
outline of the geometric model - here, the data were binned by a
factor of 8 to increase the S/N when fitting the model to the data.
The software captures the irregular shape of the shock, accounting
for angle-dependent acceleration. The shock can be identified as
the bright outer ring of the structure, while the erupting prominence
driving the shock is clearly identified as the bright inner ring
structure. Bottom: Corresponding STEREO-A EUVI 195 Å difference
images, with the geometric model plotted in blue. Right: Labeled
reference of different portions of the shock structure.
]]

[[File:532f2.png|center|thumb|600px|caption|Figure 2: 

A schematic map of the shock, with separate regions highlighted in yellow, magenta, and/or cyan
based on the performance of each model based on the time of the
peaks and the intensities of the peaks. Panels showing the combined
color maps use a CMY subtractive color model to accurately reflect
where the data is unable to differentiate between the models. The
color wheel at the top-right serves as an approximate guide, where
the color changes depending on the separation from the loci for
each model. The solid blue hexagon, for instance, represents good
agreement with both ΔTe = 0.5 (cyan) and
ΔTe = 0.25 (magenta) models
where ΔTe = 0 for complete equilibration and 1 for no
equilibration.
]]

== Conclusion ==

Non-equilibrium plasmas probably dominate the Universe, but they are hard to diagnose via remote-sensing
techniques.
A wealth of plasma physics results from Te ≠ Ti and anisotropic distribution functions,
and large-scale shock waves in the solar corona provide an excellent opportunity to study such effects.

== References ==

[1] [https://ui.adsabs.harvard.edu/abs/2013SSRv..178..633G "Electron-Ion Temperature Equilibration in Collisionless Shocks: The Supernova Remnant-Solar Wind Connection"]

[2] [https://ui.adsabs.harvard.edu/abs/2023ApJ...949...50R "Electron-Ion Temperature Ratio in Astrophysical Shocks"]

[3] [http://adsabs.harvard.edu/abs/2004A%26A...413..363M "Coronal transients and metric type II radio bursts. I. Effects of geometry"]

[4] [https://ui.adsabs.harvard.edu/abs/2011ApJ...738..160M "Observations and Interpretation of a Low Coronal Shock Wave Observed in the EUV by the SDO/AIA"]

[5] [https://ui.adsabs.harvard.edu/abs/2025ApJ...989..175T "A 3D Nonequilibrium Ionization Model of a Shock Wave in the Low Corona. I. Extreme-ultraviolet Emission and Inefficient Electron Heating"]

Electron-Ion equilibration in CME-driven shocks

2026-08-05T08:14:35Z

Hhudson: /* How do we infer plasma temperatures? */

{{Infobox Nugget |name = Nugget
|title = Electron-Ion equilibration in CME-driven shocks
|first_author = John RAYMOND
|publish_date = August 3, 2026
|next_nugget =
|previous_nugget = {{#ask: [[Category:Nugget]] [[RHESSI Nugget Index::531]]}}
}}

== Introduction ==

Coronal mass ejections
[https://en.wikipedia.org/wiki/Coronal_mass_ejection (CMEs)]
drive shock waves into regions of very low collisionality.
The jumps in density, pressure and temperature at a shock wave in dense
gas are mediated by particle collisions, and that leads to thermal
equilibrium: equal temperatures of all particle species and a Maxwellian
velocity distribution for each species.
In a low density plasma,
on the other hand, the collision lengths are large, and the shock
jump must therefore be mediated by electromagnetic fields and plasma waves.
That can lead to non-Maxwellian velocity distributions, such as Solar
Energetic Particles (SEPs), and to differing electron and ion
temperatures.

In the solar wind, postshock electron temperatures are generally
less than proton temperatures (e.g., Ref. [1])
though there is considerable scatter.
Shocks in supernova
remnants reach higher Mach numbers, and they show a trend
of decreasing electron-to-ion temperature ratio with increasing
shock speed or Mach number (Ref. [2]). CME-driven shocks
In the solar corona are more difficult to study, but they are
observed as type II radio bursts and as faint emission in UV, EUV
and white light coronagraph spectra and images (e.g., Ref. [3]).

== How do we infer plasma temperatures? ==

In some cases, it is possible to infer the electron temperature
behind a coronal shock by comparing extreme ultraviolet images from
[https://aia.lmsal.com AIA] in different bands.
When the electrons are suddenly heated in a shock, the iron ions
are successively ionized from Fe X to Fe XII to Fe XIV to Fe XVI
(The AIA 171, 193, 211 and 335 Å bands).
If the density is known from
[https://en.wikipedia.org/wiki/Solar_radio_emission type II]
radio emission or from a global MHD model of the corona, the lags
between the appearance of the shock in the
different bands indicate the electron temperature (Refs. [4,5]).
Figure 1 shows a CME-driven shock observed
on 2010 June 13, with the 3D structure inferred from AIA and STEREO
images (Ref. [5]).
Figure 2 shows the dimensionless
parameter ΔTe at different positions along the shock front,
where ΔTe = 0 corresponds to equal electron and proton
temperatures and ΔTe = 1 corresponds to no electron heating.
The intermediate values seen in Figure 2 show that these 500-700 km/s
shocks heat the electrons about half as efficiently as the ions.

[[File:532f1.png|center|thumb|600px|caption|Figure 1: 
SDO/AIA 193 Å running difference images at three different times of
the 13 June 2010 CME-driven shock wave. The blue line shows the
outline of the geometric model - here, the data were binned by a
factor of 8 to increase the S/N when fitting the model to the data.
The software captures the irregular shape of the shock, accounting
for angle-dependent acceleration. The shock can be identified as
the bright outer ring of the structure, while the erupting prominence
driving the shock is clearly identified as the bright inner ring
structure. Bottom: Corresponding STEREO-A EUVI 195 Å difference
images, with the geometric model plotted in blue. Right: Labeled
reference of different portions of the shock structure.
]]

[[File:532f2.png|center|thumb|600px|caption|Figure 2: 

A schematic map of the shock, with separate regions highlighted in yellow, magenta, and/or cyan
based on the performance of each model based on the time of the
peaks and the intensities of the peaks. Panels showing the combined
color maps use a CMY subtractive color model to accurately reflect
where the data is unable to differentiate between the models. The
color wheel at the top-right serves as an approximate guide, where
the color changes depending on the separation from the loci for
each model. The solid blue hexagon, for instance, represents good
agreement with both ΔTe = 0.5 (cyan) and
ΔTe = 0.25 (magenta) models
where ΔTe = 0 for complete equilibration and 1 for no
equilibration.
]]

== Conclusion ==

== References ==

[1] [https://ui.adsabs.harvard.edu/abs/2013SSRv..178..633G "Electron-Ion Temperature Equilibration in Collisionless Shocks: The Supernova Remnant-Solar Wind Connection"]

[2] [https://ui.adsabs.harvard.edu/abs/2023ApJ...949...50R "Electron-Ion Temperature Ratio in Astrophysical Shocks"]

[3] [http://adsabs.harvard.edu/abs/2004A%26A...413..363M "Coronal transients and metric type II radio bursts. I. Effects of geometry"]

[4] [https://ui.adsabs.harvard.edu/abs/2011ApJ...738..160M "Observations and Interpretation of a Low Coronal Shock Wave Observed in the EUV by the SDO/AIA"]

[5] [https://ui.adsabs.harvard.edu/abs/2025ApJ...989..175T "A 3D Nonequilibrium Ionization Model of a Shock Wave in the Low Corona. I. Extreme-ultraviolet Emission and Inefficient Electron Heating"]

Electron-Ion equilibration in CME-driven shocks

2026-08-05T08:11:39Z

Hhudson: No. 532 initial upload

{{Infobox Nugget |name = Nugget
|title = Electron-Ion equilibration in CME-driven shocks
|first_author = John RAYMOND
|publish_date = August 3, 2026
|next_nugget =
|previous_nugget = {{#ask: [[Category:Nugget]] [[RHESSI Nugget Index::531]]}}
}}

== Introduction ==

Coronal mass ejections
[https://en.wikipedia.org/wiki/Coronal_mass_ejection (CMEs)]
drive shock waves into regions of very low collisionality.
The jumps in density, pressure and temperature at a shock wave in dense
gas are mediated by particle collisions, and that leads to thermal
equilibrium: equal temperatures of all particle species and a Maxwellian
velocity distribution for each species.
In a low density plasma,
on the other hand, the collision lengths are large, and the shock
jump must therefore be mediated by electromagnetic fields and plasma waves.
That can lead to non-Maxwellian velocity distributions, such as Solar
Energetic Particles (SEPs), and to differing electron and ion
temperatures.

In the solar wind, postshock electron temperatures are generally
less than proton temperatures (e.g., Ref. [1])
though there is considerable scatter.
Shocks in supernova
remnants reach higher Mach numbers, and they show a trend
of decreasing electron-to-ion temperature ratio with increasing
shock speed or Mach number (Ref. [2]). CME-driven shocks
In the solar corona are more difficult to study, but they are
observed as type II radio bursts and as faint emission in UV, EUV
and white light coronagraph spectra and images (e.g., Ref. [3]).

== How do we infer plasma temperatures? ==

In some cases, it is possible to infer the electron temperature
behind a coronal shock by comparing extreme ultraviolet images from
[https://aia.lmsal.com AIA] in different bands.
When the electrons are suddenly heated in a shock, the iron ions
are successively ionized from Fe X to Fe XII to Fe XIV to Fe XVI
(The AIA 171, 193, 211 and 335 Å bands).
If the density is known from
[https://en.wikipedia.org/wiki/Solar_radio_emission type II]
radio emission or from a global MHD model of the corona, the lags
between the appearance of the shock in the
different bands indicate the electron temperature (Refs. [4,5]).
Figure 1 shows a CME-driven shock observed
on 2010 June 13, with the 3D structure inferred from AIA and STEREO
images (Ref. [5]).
Figure 2 shows the dimensionless
parameter ΔTe at different positions along the shock front,
where ΔTe = 0 corresponds to equal electron and proton
temperatures and ΔTe = 1 corresponds to no electron heating.
The intermediate values seen in Figure 2 show that these 500-700 km/s
shocks heat the electrons about half as efficiently as the ions.

[[File:532f1.png|center|thumb|600px|caption|Figure 1: 
SDO/AIA 193 Å running difference images at three different times of
the 13 June 2010 CME-driven shock wave. The blue line shows the
outline of the geometric model - here, the data were binned by a
factor of 8 to increase the S/N when fitting the model to the data.
The software captures the irregular shape of the shock, accounting
for angle-dependent acceleration. The shock can be identified as
the bright outer ring of the structure, while the erupting prominence
driving the shock is clearly identified as the bright inner ring
structure. Bottom: Corresponding STEREO-A EUVI 195 Å difference
images, with the geometric model plotted in blue. Right: Labeled
reference of different portions of the shock structure.
]]

[[File:532f2.png|center|thumb|600px|caption|Figure 2: 

Separate regions are highlighted in yellow, magenta, and/or cyan
based on the performance of each model based on the time of the
peaks and the intensities of the peaks. Panels showing the combined
color maps use a CMY subtractive color model to accurately reflect
where the data is unable to differentiate between the models. The
color wheel at the top-left serves as an approximate guide, where
the color changes depending on the separation from the loci for
each model. The solid blue hexagon, for instance, represents good
agreement with both ΔTe = 0.5 (cyan) and
ΔTe = 0.25 (magenta) models
where ΔTe = 0 for complete equilibration and 1 for no
equilibration.
]]

== Conclusion ==

== References ==

[1] [https://ui.adsabs.harvard.edu/abs/2013SSRv..178..633G "Electron-Ion Temperature Equilibration in Collisionless Shocks: The Supernova Remnant-Solar Wind Connection"]

[2] [https://ui.adsabs.harvard.edu/abs/2023ApJ...949...50R "Electron-Ion Temperature Ratio in Astrophysical Shocks"]

[3] [http://adsabs.harvard.edu/abs/2004A%26A...413..363M "Coronal transients and metric type II radio bursts. I. Effects of geometry"]

[4] [https://ui.adsabs.harvard.edu/abs/2011ApJ...738..160M "Observations and Interpretation of a Low Coronal Shock Wave Observed in the EUV by the SDO/AIA"]

[5] [https://ui.adsabs.harvard.edu/abs/2025ApJ...989..175T "A 3D Nonequilibrium Ionization Model of a Shock Wave in the Low Corona. I. Extreme-ultraviolet Emission and Inefficient Electron Heating"]

The Source Surface Height Through the Solar Cycle: A Path to Better Solar Wind Forecasts

2026-08-03T18:22:04Z

Hhudson: /* The solar cycle */

{{Infobox Nugget |name = Nugget
|title = The Source Surface Height Through the Solar Cycle: A Path to Better Solar Wind Forecasts
|number = 531
|first_author = Sandeep KUMAR
|publish_date = July 20, 2026
|next_nugget =
|previous_nugget = {{#ask: [[Category:Nugget]] [[RHESSI Nugget Index::530]]}}
}}

== Introduction ==

The potential field source surface (PFSS) model serves as the basis
of many state-of-the-art space weather forecasting frameworks,
as described in our Ref. [1].
Essentially PFSS takes the photospheric magnetic field, observable
in detail by [https://en.wikipedia.org/wiki/Zeeman_effect Zeeman effect]
spectroscopy, and uses it to extrapolate into the solar corona.
This requires the assumption of just a single parameter: the radial
distance of the "source surface", a fictitious sphere separating
radial field of the solar wind, from the structured field of the photosphere.
Mathematically any field induced by external sources can be represented by a
fitting
[https://en.wikipedia.org/wiki/Potential_theory spherical harmonic]
functions at its boundaries.
This is tractable but physically it may seem terribly wrong,
since it ignores all coronal field sources (currents) within the volume itself.
But it works surprisingly well, perhaps because the currents that we
know to be present only make a minor perturbation of the basic potential
field.

== The nature of the source surface ==

The PFSS model contains only a single free parameter, the source surface
height, at which magnetic field lines are assumed to be exactly radial.
A value of 2.5 R⊙ for the source-surface height has
traditionally been adopted in most studies.
Optimizing the source-surface value significantly improves model forecasts
of the solar-wind speed as observed at the L1
[https://science.nasa.gov/solar-system/resources/faq/what-are-lagrange-points/ Lagrangian point],
just upstream of Earth in the
[https://en.wikipedia.org/wiki/Solar_wind solar wind] (Ref. [1]).
This study employed two types ("HU STD" and "HU ZPC"] of
([https://en.wikipedia.org/wiki/Global_Oscillations_Network_Group GONG)
synoptic magnetic field maps.
The fidelity of these data
was confirmed by comparing the extrapolated global
magnetic field structures with the large-scale corona observed in
the extended field of view of the PROBA2/SWAP images as shown in
Figure 1.

[[File:531f1.png|center|thumb|600px|caption|Figure 1: 
PFSS-extrapolated magnetic field lines overlaid on the
[https://www.cosmos.esa.int/web/proba-2/swap SWAP]
(top and bottom panel) image of 20 August 2017, 10:45 UT. The middle
panel shows the SWAP mosaic without PFSS extrapolation. The top
left panel shows PFSS extrapolation with HU STD map, and the bottom
left panel with HU ZPC map (on 20 August 2017, 12:14 UT). The right
column shows the zoomed-in version of the white rectangle on the
left panels.
]]

== The solar cycle ==

How must the PFSS model evolve through the
[https://www.spaceweather.gov/products/solar-cycle-progression solar cycle],
during which the solar wind obviously changes substantially?
In Ref. [3] we carried out one of the most comprehensive and
long-term studies of
SS height optimisation for solar wind prediction at L1, analyzing
synoptic magnetograms from both space-based
([http://hmi.stanford.edu SDO/HMI]) and ground-based
([https://gong.nso.edu GONG]) observatories, across nearly three solar cycles, SC23-SC25.
This optimization used the PFSS parameters in the model of Ref. [2] to
compare with the wind-speed observations.
Our main finding is that the optimal SS height varies systematically
with the solar cycle: higher SS heights (≥2.5 R⊙) provide better
solar wind speed predictions during solar minimum, whereas lower
SS heights (<2.5 R⊙) perform better during solar maximum, suggesting
a relationship between SS height and SC phase over long timescales.
We also found that the optimized SS height depends on the choice
of magnetogram, whereas the pattern remains similar for a given
choice of magnetograms. The HMI and GONG "ZPC" magnetograms perform
similarly, and both provide better forecasting than GONG "STD" maps,
as shown in Figure 2. The results provide strong evidence
that solar-cycle-dependent optimization of the PFSS source surface
height is a practical way to improve solar wind forecasting, which
serves as the foundation for heliospheric models.

[[File:531f2.png|center|thumb|600px|caption|Figure 2: 
Top panel: the source-surface radial height, in black for the standard
fixed value of 2.5 RR⊙ and in blue and gold for two
alternative optimizations.
The time range covers the 100
[https://en.wikipedia.org/wiki/Solar_rotation Carrington rotations]
from January 2018 (solar minimum) to July 2025 (high activity).
The lower panel shows Pearson correlation coefficients for predictions of
the solar-wind speed.
]]

== Conclusions ==

Our adjusted PFSS radii clearly improve forecasts of the solar-wind speed.
The solar wind however does not flow in a spherically symmetric manner,
either near the corona or far out in the heliosphere.
Thus it is not surprising that even the optimizations do not yield very
strong correlation coefficients.
We anticipate much greater improvements from future modeling frameworks outside
that of spherical symmetry.

== References ==

[1] [https://ui.adsabs.harvard.edu/abs/2025JSWSC..15...24K "On the role of source surface height and magnetograms in solar wind forecast accuracy"]

[2] [http://adsabs.harvard.edu/abs/2015SpWea..13..154R "On the role played by magnetic expansion factor in the prediction of solar wind speed"]

[3] [https://ui.adsabs.harvard.edu/abs/2026ApJ..1006...26K "Source Surface Height Optimization for Improved Solar Wind Velocity Forecasting across Solar Cycles 23, 24, and 25"]

The Source Surface Height Through the Solar Cycle: A Path to Better Solar Wind Forecasts

2026-08-03T16:55:04Z

Hhudson: /* The solar cycle */

{{Infobox Nugget |name = Nugget
|title = The Source Surface Height Through the Solar Cycle: A Path to Better Solar Wind Forecasts
|number = 531
|first_author = Sandeep KUMAR
|publish_date = July 20, 2026
|next_nugget =
|previous_nugget = {{#ask: [[Category:Nugget]] [[RHESSI Nugget Index::530]]}}
}}

== Introduction ==

The potential field source surface (PFSS) model serves as the basis
of many state-of-the-art space weather forecasting frameworks,
as described in our Ref. [1].
Essentially PFSS takes the photospheric magnetic field, observable
in detail by [https://en.wikipedia.org/wiki/Zeeman_effect Zeeman effect]
spectroscopy, and uses it to extrapolate into the solar corona.
This requires the assumption of just a single parameter: the radial
distance of the "source surface", a fictitious sphere separating
radial field of the solar wind, from the structured field of the photosphere.
Mathematically any field induced by external sources can be represented by a
fitting
[https://en.wikipedia.org/wiki/Potential_theory spherical harmonic]
functions at its boundaries.
This is tractable but physically it may seem terribly wrong,
since it ignores all coronal field sources (currents) within the volume itself.
But it works surprisingly well, perhaps because the currents that we
know to be present only make a minor perturbation of the basic potential
field.

== The nature of the source surface ==

The PFSS model contains only a single free parameter, the source surface
height, at which magnetic field lines are assumed to be exactly radial.
A value of 2.5 R⊙ for the source-surface height has
traditionally been adopted in most studies.
Optimizing the source-surface value significantly improves model forecasts
of the solar-wind speed as observed at the L1
[https://science.nasa.gov/solar-system/resources/faq/what-are-lagrange-points/ Lagrangian point],
just upstream of Earth in the
[https://en.wikipedia.org/wiki/Solar_wind solar wind] (Ref. [1]).
This study employed two types ("HU STD" and "HU ZPC"] of
([https://en.wikipedia.org/wiki/Global_Oscillations_Network_Group GONG)
synoptic magnetic field maps.
The fidelity of these data
was confirmed by comparing the extrapolated global
magnetic field structures with the large-scale corona observed in
the extended field of view of the PROBA2/SWAP images as shown in
Figure 1.

[[File:531f1.png|center|thumb|600px|caption|Figure 1: 
PFSS-extrapolated magnetic field lines overlaid on the
[https://www.cosmos.esa.int/web/proba-2/swap SWAP]
(top and bottom panel) image of 20 August 2017, 10:45 UT. The middle
panel shows the SWAP mosaic without PFSS extrapolation. The top
left panel shows PFSS extrapolation with HU STD map, and the bottom
left panel with HU ZPC map (on 20 August 2017, 12:14 UT). The right
column shows the zoomed-in version of the white rectangle on the
left panels.
]]

== The solar cycle ==

How must the PFSS model evolve through the
[https://www.spaceweather.gov/products/solar-cycle-progression solar cycle],
during which the solar wind obviously changes substantially?
In Ref. [3] we carried out one of the most comprehensive and
long-term studies of
SS height optimisation for solar wind prediction at L1, analyzing
synoptic magnetograms from both space-based
([http://hmi.stanford.edu SDO/HMI]) and ground-based
(GONG) observatories, across nearly three solar cycles, SC23-SC25.
This optimization used the PFSS parameters in the model of Ref. [2] to
compare with the wind-speed observations.
Our main finding is that the optimal SS height varies systematically
with the solar cycle: higher SS heights (≥2.5 R⊙) provide better
solar wind speed predictions during solar minimum, whereas lower
SS heights (<2.5 R⊙) perform better during solar maximum, suggesting
a relationship between SS height and SC phase over long timescales.
We also found that the optimized SS height depends on the choice
of magnetogram, whereas the pattern remains similar for a given
choice of magnetograms. The HMI and GONG ZPC magnetograms perform
similarly, and both provide better forecasting than GONG STD maps,
as shown in Figures 2 and 3. The results provide strong evidence
that solar-cycle-dependent optimization of the PFSS source surface
height is a practical way to improve solar wind forecasting, which
serves as the foundation for heliospheric models.

[[File:531f2.png|center|thumb|600px|caption|Figure 2: 
Top panel: the source-surface radial height, in black for the standard
fixed value of 2.5 RR⊙ and in blue and gold for two
alternative optimizations.
The time range covers the 100
[https://en.wikipedia.org/wiki/Solar_rotation Carrington rotations]
from January 2018 (solar minimum) to July 2025 (high activity).
The lower panel shows Pearson correlation coefficients for predictions of
the solar-wind speed.
]]

== Conclusions ==

Our adjusted PFSS radii clearly improve forecasts of the solar-wind speed.
The solar wind however does not flow in a spherically symmetric manner,
either near the corona or far out in the heliosphere.
Thus it is not surprising that even the optimizations do not yield very
strong correlation coefficients.
We anticipate much greater improvements from future modeling frameworks outside
that of spherical symmetry.

== References ==

[1] [https://ui.adsabs.harvard.edu/abs/2025JSWSC..15...24K "On the role of source surface height and magnetograms in solar wind forecast accuracy"]

[2] [http://adsabs.harvard.edu/abs/2015SpWea..13..154R "On the role played by magnetic expansion factor in the prediction of solar wind speed"]

[3] [https://ui.adsabs.harvard.edu/abs/2026ApJ..1006...26K "Source Surface Height Optimization for Improved Solar Wind Velocity Forecasting across Solar Cycles 23, 24, and 25"]

File:531f2.png

2026-08-03T16:54:01Z

Hhudson: