Diagnostics of electron beam properties from the simultaneous hard X-ray and microwave emission in the 10 March 2001 flare

TL;DR

This study models and interprets simultaneous hard X-ray and microwave emissions from a solar flare using a kinetic electron beam model, achieving close fits to observed data and revealing the effects of electric fields and magnetic convergence.

Contribution

The paper applies a time-dependent Fokker-Planck model to interpret simultaneous HXR and MW emissions in a solar flare, incorporating electric fields and magnetic convergence effects for the first time.

Findings

Double power law HXR spectrum fitted by models with electric field effects.

MW emission simulations closely match observed high-frequency features.

Moderate magnetic convergence improves fit to microwave data.

Abstract

Simultaneous simulation of HXR and MW emission with the same populations of electrons is still a great challenge for interpretation of observations in real events. In this paper we apply the FP kinetic model of precipitation of electron beam with energy range from 12 keV to 1.2 MeV to the interpretation of X-ray and microwave emissions observed in the flare of 10 March 2001. Methods. The theoretical HXR and MW emissions were calculated by using the distribution functions of electron beams found by solving time-dependent Fokker-Planck approach in a converging magnetic field (Zharkova at al., 2010; Kuznetsov and Zharkova, 2010) for anisotropic scattering of beam electrons on the ambient particles in Coloumb collisions and Ohmic losses. The simultaneous observed HXR photon spectra and frequency distribution of MW emission and polarization were fit by those simulated from FP models which include the effects of electric field induced by beam electrons and precipitation into a converging magnetic loop. Magnetic field strengths in the footpoints on the photosphere were updated with newly calibrated SOHO/MDI data. The observed HXR energy spectrum above 10 keV is shown to be a double power law which was fit precisely by the photon HXR spectrum simulated for the model including the self-induced electric field but without magnetic convergence. The MW emission simulated for different models of electron precipitation revealed a better fit to the observed distribution at higher frequencies for the models combining collisions and electric field effects with a moderate magnetic field convergence of 2. The MW simulations were able to reproduce closely the main features of the MW emission observed at higher frequencies.