Derivation of Stochastic Acceleration Model Characteristics for Solar Flares From RHESSI Hard X-Ray Observations

TL;DR

This paper introduces a new method to derive electron spectra and key parameters of stochastic acceleration models from RHESSI hard X-ray data, providing insights into turbulence and scattering in solar flare regions.

Contribution

The paper presents a novel approach to extract acceleration model parameters directly from high-resolution X-ray observations, advancing understanding of particle acceleration in solar flares.

Findings

Evidence of strong scattering and turbulence in the acceleration region.

High-density turbulence energy with a steep spectrum detected.

Electron spectra consistent with stochastic acceleration models.

Abstract

The model of stochastic acceleration of particles by turbulence has been successful in explaining many observed features of solar flares. Here we demonstrate a new method to obtain the accelerated electron spectrum and important acceleration model parameters from the high resolution hard X-ray observations provided by the Reuven Ramaty High Energy Solar Spectroscopic Imager (RHESSI). In our model, electrons accelerated at or very near the loop top produce thin target bremsstrahlung emission there and then escape downward producing thick target emission at the loop footpoints. Based on the electron flux spectral images obtained by the regularized inversion of the RHESSI count visibilities, we derive several important parameters for the acceleration model. We apply this procedure to the 2003 November 03 solar flare, which shows a loop top source up to 100--150 keV in hard X-ray with a relatively flat spectrum in addition to two footpoint sources. The results imply presence of strong scattering and a high density of turbulence energy with a steep spectrum in the acceleration region.