Plasma heating in solar flares and their soft and hard X-ray emissions

TL;DR

This study models plasma heating in solar flares using non-thermal electrons and hydrodynamic simulations, successfully explaining observed X-ray emissions with electron beam-driven evaporation, highlighting the model's strengths and limitations.

Contribution

It introduces a detailed 1D hydrodynamic model incorporating Fokker-Planck formalism to simulate X-ray emissions in solar flares, demonstrating electron beams as the primary heating mechanism.

Findings

Model aligns well with observations for the June 2002 flare.

Synthesized emissions are within 30% of observed values.

Soft and hard X-ray emissions can be explained by electron beam-driven evaporation.

Abstract

In this paper, the energy budgets of two single-loop like flares observed in X- ray are analysed under the assumption that non-thermal electrons (NTEs) are the only source of plasma heating during all phases of both events. The flares were observed by RHESSI and GOES on February 20th, 2002 and June 2nd, 2002, respectively. Using a 1D hydrodynamic code for both flares the energy deposited in the chromosphere was derived applying RHESSI observational data. The use of the Fokker-Planck formalism permits the calculation of distributions of the NTEs in flaring loops, thus spatial distributions of the X-ray non-thermal emissions and integral fluxes for the selected energy ranges which were compared with the observed ones. The best compatibility of the model with the observations was obtained for the June 2nd, 2002 event in both the 0.5-4 A GOES range and total fluxes in the 6-12 keV, 12-25 keV, 20-25 keV and 50- 100 keV energy bands. Results of photometry of the individual flaring structures in a high energy range shows that the best compliance occurred for the June 2nd, 2002 flare, where the synthesized emissions were 30% or more higher than the observed emissions. Some part of these differences may be caused by inevitable flaws of the applied methodology, like by an assumption that the model of the flare is symmetric and there are no differences in the emissions originating from the feet of the flare's loop and by relative simplicity of the applied numerical 1D code and procedures. Despite these problems, a collation of modelled results with observations shows that soft and hard X-ray emissions observed for analysed single-loop like events may be fully explained by electron beam-driven evaporation only.