Spatially inhomogeneous acceleration of electrons in solar flares

TL;DR

This paper introduces a spatially distributed acceleration model for electrons in solar flares, demonstrating that inhomogeneous acceleration regions significantly influence observed X-ray spectra and differ from traditional leaky-box predictions.

Contribution

It presents the first spatially distributed acceleration model for solar flare electrons, highlighting the impact of inhomogeneous acceleration regions on spectral properties.

Findings

Inhomogeneous acceleration regions produce softer spectral indices.

Spatial variation significantly affects electron acceleration modeling.

Results differ from traditional leaky-box solutions.

Abstract

The imaging spectroscopy capabilities of the Reuven Ramaty high energy solar spectroscopic imager (RHESSI) enable the examination of the accelerated electron distribution throughout a solar flare region. In particular, it has been revealed that the energisation of these particles takes place over a region of finite size, sometimes resolved by RHESSI observations. In this paper, we present, for the first time, a spatially distributed acceleration model and investigate the role of inhomogeneous acceleration on the observed X-ray emission properties. We have modelled transport explicitly examining scatter-free and diffusive transport within the acceleration region and compare with the analytic leaky-box solution. The results show the importance of including this spatial variation when modelling electron acceleration in solar flares. The presence of an inhomogeneous, extended acceleration region produces a spectral index that is, in most cases, different from the simple leaky-box prediction. In particular, it results in a generally softer spectral index than predicted by the leaky-box solution, for both scatter-free and diffusive transport, and thus should be taken into account when modelling stochastic acceleration in solar flares.