Mars Odyssey/HEND and RHESSI
| Nugget | |
|---|---|
| Number: | 200 |
| 1st Author: | V. Vybornov |
| 2nd Author: | M. Livshits |
| Published: | June 10, 2013 |
| Next Nugget: | |
| Previous Nugget: | Hard X-rays in Descent |
Introduction
Mars Odyssey may be little-known to solar physicists, but its HEND (High-Energy Neutron Detector) readily detects solar flares. Generally, flare observations are performed from the Earth or near-Earth orbits. However, there are space missions that operate at various ecliptic longitudes and latitudes in interplanetary space; these can provide different vantage points for solar observations. HEND recorded hard X-ray and gamma-radiation from 40 keV to 2 MeV (Ref. [1]), as a part of the Mars Odyssey mission, and observed solar flares from the middle of 2001 up to 2011. The main working parts of HEND comprise an outer scintillation counter of CsI (energy band from 40 to 1000 keV) plus an inner plastic one, (Stilbene) for the range 300 – 2000 keV. Two types of data are available: the time profiles from the outer and inner scintillators with a resolution of 0.25 s (near 80 keV) and 1 s (near 330 keV) respectively, and spectral data with a resolution of 20 s in 15 energy channels from both scintillators.
In this Nugget we discuss observations of flares visible from the Earth, as a check on the HEND calibrations, and then show observations from the solar hemisphere (the "backside") invisible from Earth.
Simultaneous HEND and RHESSI observations
The HEND observations of flares on the visible hemisphere basically just supplement the data obtained by other missions on near-Earth orbits, but they may fill in vital gaps in these data.
Particularly, it concerns the data on large solar flares, when some satellites were disabled. For instance, fig. 1 illustrates a good agreement between the profiles obtained by HEND and RHESSI. Interesting are also observations from various directions, as well as observations of events that are seen wholly from one spacecraft, while the other can only record the associated effects. One of such events was the flare of 27 October 2002, which was fully on the invisible side of the Sun.
References
[1] Maps of Subsurface Hydrogen from the High Energy Neutron Detector, Mars Odyssey