Drift-Kinetic Modeling of Particle Acceleration and Transport in Solar Flares

TL;DR

This paper presents a drift-kinetic model for simulating particle acceleration and transport in solar flares, revealing two main acceleration mechanisms and their observational implications.

Contribution

The study introduces a numerical drift-kinetic simulation approach to directly compare particle dynamics in solar flares with observations, highlighting two key acceleration processes.

Findings

Betatron acceleration at loop tops enhances perpendicular electron velocities.

Inertia drift acceleration in open fields produces antisunward electrons.

Electron velocity distributions deviate from isotropy, affecting emissions and in-situ observations.

Abstract

Based on the drift-kinetic theory, we develop a model for particle acceleration and transport in solar flares. The model describes the evolution of the particle distribution function by means of a numerical simulation of the drift-kinetic Vlasov equation, which allows us to directly compare simulation results with observations within an actual parameter range of the solar corona. Using this model, we investigate the time evolution of the electron distribution in a flaring region. The simulation identifies two dominant mechanisms of electron acceleration. One is the betatron acceleration at the top of closed loops, which enhances the electron velocity perpendicular to the magnetic field line. The other is the inertia drift acceleration in open magnetic field lines, which produces antisunward electrons. The resulting velocity space distribution significantly deviates from an isotropic distribution. The former acceleration can be a generation mechanism of electrons that radiate loop-top nonthermal emissions, and the latter be of escaping electrons from the Sun that should be observed by in-situ measurements in interplanetary space and resulting radio bursts through plasma instabilities.