Hybrid simulations of chromospheric HXR flare sources

TL;DR

This study uses a hybrid simulation code to model electron beam propagation and chromospheric response during solar flares, aiming to reconcile observed HXR source sizes and positions with theoretical predictions.

Contribution

It introduces a self-consistent hybrid modeling approach that combines electron transport and chromospheric dynamics to better match RHESSI observations.

Findings

Simulated HXR source sizes and positions align more closely with observations.

The model reveals the importance of dynamic chromospheric response in HXR source morphology.

Results suggest modifications to the standard collisional thick target model are needed.

Abstract

Recent measurements of vertical extents and positions of the chromospheric hard X-ray (HXR) flare sources based on Ramaty High-Energy Spectroscopic Imager (RHESSI) observations show a significant inconsistency with the theoretical predictions based on the standard collisional thick target model (CTTM). Using a hybrid flare code Flarix, we model simultaneously and self-consistently the propagation, scattering and energy losses of electron beams with power-law energy spectra and various initial pitch-angle distributions in a purely collisional approximation and concurrently the dynamic response of the heated chromosphere on timescales typical for RHESSI image reconstruction. The results of the simulations are used to model the time evolution of the vertical distribution of chromospheric HXR source within a singular (compact) loop. Adopting the typical RHESSI imaging times scales, energy dependent vertical sizes and positions as could be observed by RHESSI are presented.