Non-thermal Electron Energization During the Impulsive Phase of an X9.3 Flare Revealed by Insight-HXMT

• Published in: The Astrophysical journal Vol. 918; no. 2; pp. 42 - 51
• Main Authors: Zhang, P., Wang, W., Su, Y., Song, L. M., Li, C. K., Zhou, D. K., Zhang, S. N., Tian, H., Liu, S. M., Zhao, H. S., Zhang, S.
• Format: Journal Article
• Language: English
• Published: Philadelphia The American Astronomical Society 01-09-2021; IOP Publishing
• Subjects: Astrophysics; Corona; Electron density; Evolution; Field strength; Gamma ray fluxes; Gamma rays; Light curve; Magnetic fields; Magnetic reconnection; Solar flares; Spectra; Spectral analysis; Spectrum analysis; X ray telescopes
• ISSN: 0004-637X; 1538-4357
• DOI: 10.3847/1538-4357/ac0cfb

Abstract
The X9.3 flare SOL20170906T11:55 was observed by the CsI detector aboard the first Chinese X-ray observatory Hard X-ray Modulation telescope (Insight-HXMT). Using the wavelets method, we report 22 s quasiperiodic pulsations during the impulsive phase. The spectra from 100 keV to 800 keV show the evolution with the gamma-ray flux of a power-law photon index from ∼1.8 before the peak, ∼2.0 around the flare peak, to ∼1.8 again. The gyrosynchrotron microwave spectral analysis reveals a 36.″6 ± 0.″6 radius gyrosynchrotron source with mean transverse magnetic field around 608.2 Gauss. The penetrated ≥10 keV non-thermal electron density is about 10
6.7
cm
−3
at peak time. The magnetic field strength followed the evolution of high-frequency radio flux. Further gyrosynchrotron source modeling analysis implies that there exists a quite steady gyrosynchrotron source, and the non-thermal electron density and transverse magnetic field evolution are similar to higher-frequency light curves. The temporal spectral analysis reveals that those non-thermal electrons are accelerated by repeated magnetic reconnection, likely from a lower corona source.