Aschwanden, M. J., Holman, G., O’Flannagain, A., Caspi, A., McTiernan, J. M. and Kontar, E. P. (2016) Global energetics of solar flares. III. Nonthermal energies. Astrophysical Journal, 832(1), 27. (doi: 10.3847/0004-637X/832/1/27)
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Abstract
This study entails the third part of a global flare energetics project, in which Ramaty High-Energy Solar Spectroscopic Imager (RHESSI) data of 191 M and X-class flare events from the first 3.5 years of the Solar Dynamics Observatory mission are analyzed. We fit a thermal and a nonthermal component to RHESSI spectra, yielding the temperature of the differential emission measure (DEM) tail, the nonthermal power-law slope and flux, and the thermal/nonthermal cross-over energy eco. From these parameters, we calculate the total nonthermal energy Ent in electrons with two different methods: (1) using the observed cross-over energy eco as low-energy cutoff, and (2) using the low-energy cutoff ewt predicted by the warm thick-target bremsstrahlung model of Kontar et al. Based on a mean temperature of Te = 8.6 MK in active regions, we find low-energy cutoff energies of ewt = 6.2 1.6 keV for the warm-target model, which is significantly lower than the cross-over energies eco = 21 6 keV. Comparing with the statistics of magnetically dissipated energies Emag and thermal energies Eth from the two previous studies, we find the following mean (logarithmic) energy ratios with the warm-target model: Ent mag = 0.41 E , Eth mag = 0.08 E , and Eth n = 0.15 E t. The total dissipated magnetic energy exceeds the thermal energy in 95% and the nonthermal energy in 71% of the flare events, which confirms that magnetic reconnection processes are sufficient to explain flare energies. The nonthermal energy exceeds the thermal energy in 85% of the events, which largely confirms the warm thick-target model.
Item Type: | Articles |
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Status: | Published |
Refereed: | Yes |
Glasgow Author(s) Enlighten ID: | Kontar, Professor Eduard |
Authors: | Aschwanden, M. J., Holman, G., O’Flannagain, A., Caspi, A., McTiernan, J. M., and Kontar, E. P. |
College/School: | College of Science and Engineering > School of Physics and Astronomy |
Journal Name: | Astrophysical Journal |
Publisher: | IOP Publishing |
ISSN: | 0004-637X |
ISSN (Online): | 1538-4357 |
Published Online: | 14 November 2016 |
Copyright Holders: | Copyright © 2016 The American Astronomical Society |
First Published: | First published in Astrophysical Journal 832(1): 27 |
Publisher Policy: | Reproduced in accordance with the publisher copyright policy |
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