A Unified Computational Model for Solar and Stellar Flares

TL;DR

This paper introduces a unified computational model for solar and stellar flares, simulating how accelerated charged particles heat stellar atmospheres and produce observable brightening, with detailed physics and parameter studies.

Contribution

The work presents a novel unified framework that models impulsive flares on both the Sun and dMe stars using particle beam propagation and radiative transfer, incorporating return currents.

Findings

Atmospheric response depends strongly on particle cutoff energy.

Spectral index significantly influences flare heating.

Model predictions align with observational data.

Abstract

We present a unified computational framework which can be used to describe impulsive flares on the Sun and on dMe stars. The models assume that the flare impulsive phase is caused by a beam of charged particles that is accelerated in the corona and propagates downward depositing energy and momentum along the way. This rapidly heats the lower stellar atmosphere causing it to explosively expand and dramatically brighten. Our models consist of flux tubes that extend from the sub-photosphere into the corona. We simulate how flare-accelerated charged particles propagate down one-dimensional flux tubes and heat the stellar atmosphere using the Fokker-Planck kinetic theory. Detailed radiative transfer is included so that model predictions can be directly compared with observations. The flux of flare-accelerated particles drives return currents which additionally heat the stellar atmosphere. These effects are also included in our models. We examine the impact of the flare-accelerated particle beams on model solar and dMe stellar atmospheres and perform parameter studies varying the injected particle energy spectra. We find the atmospheric response is strongly dependent on the accelerated particle cutoff energy and spectral index.