Particle acceleration by strong turbulence in solar flares: theory of spectrum evolution

TL;DR

This paper develops a nonlinear model for particle acceleration in solar flares, showing how the interaction with turbulence leads to evolving energy spectra that match observed X-ray and gamma-ray emissions.

Contribution

It introduces a self-consistent simulation of particle-turbulence interaction, revealing spectrum evolution patterns dependent on injection efficiency.

Findings

Spectra evolve from soft-hard-soft or soft-hard-harder patterns.

Nonlinear coupling significantly influences particle energy distribution.

Model aligns with observed emission patterns in solar flares.

Abstract

We propose a nonlinear self-consistent model of the turbulent non-resonant particle acceleration in solar flares. We simulate temporal evolution of the spectra of charged particles accelerated by strong long-wavelength MHD turbulence taking into account back reaction of the accelerated particles on the turbulence. The main finding is that the nonlinear coupling of accelerated particles and MHD turbulence result in prominent evolution of the spectra of accelerated particles, which can be either soft-hard-soft or soft-hard-harder depending on the particle injection efficiency. Such evolution patterns are widely observed in hard X-ray and gamma-ray emission from solar flares.