Combined Modeling of Acceleration, Transport, and Hydrodynamic Response in Solar Flares: I. The Numerical Model

TL;DR

This paper presents a self-consistent numerical model combining particle acceleration, transport, and plasma hydrodynamics in solar flares, revealing how low-energy electrons influence heating and X-ray emissions.

Contribution

It introduces a novel integrated modeling approach that accurately simulates particle transport and plasma response in solar flares, including realistic electron spectra.

Findings

More heating occurs in the corona due to low-energy electrons.

Enhanced X-ray emission is linked to density jumps at evaporation fronts.

The model predicts stronger chromospheric evaporation than previous studies.

Abstract

Acceleration and transport of high-energy particles and fluid dynamics of atmospheric plasma are interrelated aspects of solar flares. We present here self-consistently combined Fokker-Planck modeling of particles and hydrodynamic simulation of flare plasma. Energetic electrons are modeled with the Stanford unified code of acceleration, transport, and radiation, while plasma is modeled with the NRL flux tube code. We calculated the collisional heating rate from the particle transport code, which is more accurate than those based on approximate analytical solutions. We used a realistic spectrum of injected electrons provided by the stochastic acceleration model, which has a smooth transition from a quasi-thermal background at low energies to a nonthermal tail at high energies. The inclusion of low-energy electrons results in relatively more heating in the corona (vs. chromosphere), a larger downward conductive flux, and thus a stronger chromospheric evaporation than obtained in previous studies, which had a deficit in low-energy electrons due to an arbitrarily assumed low-energy cutoff. The energy and spatial distributions of energetic electrons and bremsstrahlung photons bear signatures of the changing density distribution caused by chromospheric evaporation. In particular, the density jump at the evaporation front gives rise to enhanced X-ray emission.