Analysis of Kinetic Process of Energetic Electron During a Flare on 2004 December 1

Abstract

We analyze the M1.1 flare event peaked at 07:20:00 UT on 2004 December 1 mainly from radio and hard X-ray (HXR) observations. By eliminating the thermal component from the observed total radio emission flux, the non-thermal part of the radio and HXR burst process is investigated in a self-consistent way. The spectral index of energetic electrons deduced from the radio burst evolves as a Soft-Hard-Hard pattern and that from HXR as a Soft-Hard-Soft pattern corresponding to an initial-main-decay phase. The trap-plus-precipitation model is applied in the kinetic process of energetic electrons for this flare event. The radio fluxes at six frequencies selected from the 2.6-7.6 GHz range are fitted with a gyrosynchrotron radiation mechanism. It is found that a linearly increasing electron escape rate can best fit to the observed radio fluxes from 07:00:00 UT to 07:40:00 UT and the slope of the electron escape rate for the six selected frequencies decreases with increasing frequency. During the decay phase from 07:15:00 UT to 07:20:00 UT, the hardened spectrum of the radio burst may be due to the increasing amount of trapped electrons with higher energy by a lower escape rate. Meanwhile, the increasing amount of precipitating electrons with a lower energy band may soften the HXR spectrum. In the decay phase after 07:20:00 UT, thermal emission is the dominating component for the radio burst.