Electron Energy Spectra and e-e Bremsstrahlung from Anisotropic Electron Distributions in Extreme Solar Flares

• Published in: arXiv.org 2020-12
• Main Authors: Oparin, I D, Charikov, Yu E, Ovchinnikova, E P, Shabalin, A N
• Format: Article
• Language: English
• Subjects: Anisotropy; Bremsstrahlung; Electron energy; Electron transport; Energy spectra; Gamma rays; Pitch (inclination); Power law; Solar flares; X ray spectra
• ISSN: 2331-8422
• DOI: 10.48550/arxiv.2012.07908

We study the electron energy spectra of two powerful solar flares SOL2003-10-28T 11:06:16 (GOES class X17.2) and SOL2002-07-23T00:18:16 (X4.8) on the basis of HXR and gamma-ray spectra obtained from RHESSI data. Electron-electron (e-e) bremsstrahlung makes a significant contribution to the X-ray flux at energies above 500 keV. In X-ray flux calculations different electron pitch-angle distributions were considered: quasi-transverse and quasi-longitudinal. It was shown that breaks in hard X-ray spectra occur on energies \(\epsilon\approx100\) keV with photon spectral-index difference \(\Delta\gamma\ge 1\) in the case of quasi-longitudinal anisotropy and hard power-law electron energy spectra. We deduce the parameters of non-thermal electrons energy spectra from RHESSI data for the extreme solar flares of 2003 October 28 and 2002 July 23. After including e-e bremsstrahlung, the non-thermal electrons energy spectra obtained in the thick-target model can be fitted using power-law with spectral index \(\delta\approx 5\). For the 2002 July 23 flare, there is a pronounced asymmetry towards the southern footpoint, starting from energies above 100 keV. The separation of HXR sources at energies above 100 keV may be related to a feature of relativistic electron transport in flaring loops.