Elementary Energy Release Events in Solar Flares

TL;DR

This paper introduces a phenomenological model linking turbulence evolution to particle acceleration in solar flares, explaining observed X-ray pulse patterns and their spectral changes.

Contribution

It presents a new stochastic acceleration model that connects turbulence intensity with electron acceleration and reproduces observed X-ray spectral patterns.

Findings

Electron acceleration depends on small-scale turbulence intensity.

The model reproduces the soft-hard-soft X-ray pulse pattern.

Flux and spectral index correlations change during pulse phases.

Abstract

Most theoretical investigations of particle acceleration during solar flares cannot be applied to observations for detailed study of the time evolution. We propose a phenomenological model for turbulence evolution and stochastic particle acceleration that links observations to the energy release and particle acceleration through two coefficients characterizing particle interactions with turbulent electromagnetic fields. In the linear regime the particle distribution does not affect the turbulence energy cascade. It is shown that electron acceleration critically depends on the intensity of small-scale turbulence and an impulsive non-thermal component only appears near the peak of the gradually evolving turbulence intensity. The model naturally reproduces the soft-hard-soft pattern of hard X-ray pulses, and we attribute the observed change in flux and spectral index correlation from the rise to decay phase of some pulses to changes in the background plasma. Detailed modeling of well-observed individual events will probe the energy release processes.