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Low-Energy Cutoffs in Electron Spectra of Solar Flares: Statistical Survey.
- Source :
-
Solar Physics . Oct2008, Vol. 252 Issue 1, p139-147. 9p. 1 Chart, 5 Graphs. - Publication Year :
- 2008
-
Abstract
- The Reuven Ramaty High Energy Spectroscopic Imager (RHESSI) X-ray data base (February 2002 – May 2006) has been searched to find solar flares with weak thermal components and flat photon spectra. Using a regularized inversion technique, we determine the mean electron flux distribution from count spectra for a selection of events with flat photon spectra in the 15 – 20 keV energy range. Such spectral behavior is expected for photon spectra either affected by photospheric albedo or produced by electron spectra with an absence of electrons in a given energy range ( e.g., a low-energy cutoff in the mean electron spectra of nonthemal particles). We have found 18 cases that exhibit a statistically significant local minimum (a dip) in the range of 13 – 19 keV. The positions and spectral indices of events with low-energy cutoff indicate that such features are likely to be the result of photospheric albedo. It is shown that if the isotropic albedo correction is applied, all low-energy cutoffs in the mean electron spectrum are removed, and hence the low-energy cutoffs in the mean electron spectrum of solar flares above ∼ 12 keV cannot be viewed as real features. If low-energy cutoffs exist in the mean electron spectra, their energies should be less than ∼ 12 keV. [ABSTRACT FROM AUTHOR]
- Subjects :
- *SOLAR flares
*SPECTRUM analysis
*X-rays
*PHOTONS
*SURVEYS
Subjects
Details
- Language :
- English
- ISSN :
- 00380938
- Volume :
- 252
- Issue :
- 1
- Database :
- Academic Search Index
- Journal :
- Solar Physics
- Publication Type :
- Academic Journal
- Accession number :
- 34561035
- Full Text :
- https://doi.org/10.1007/s11207-008-9249-x