Particle Acceleration by Fast Modes in Solar Flares

TL;DR

This paper investigates how fast magnetosonic modes in solar flares accelerate particles, finding transit time damping as the dominant mechanism and demonstrating potential for electrons to reach GeV energies.

Contribution

It extends previous models by going beyond quasilinear approximation and compares different damping mechanisms in particle acceleration during solar flares.

Findings

Transit time damping dominates particle acceleration.

Protons are confined during acceleration due to scattering.

Electrons can be accelerated to GeV energies in solar flare conditions.

Abstract

We address the problem of particle acceleration in solar flares by fast modes which may be excited during the reconnection and undergo cascade and are subjected to damping. We extend the calculations beyond quasilinear approximation and compare the acceleration and scattering by transit time damping and gyroresonance interactions. We find that the acceleration is dominated by the so called transit time damping mechanism. We estimate the total energy transferred into particles, and show that our approach provides sufficiently accurate results We compare this rate with energy loss rate. Scattering by fast modes appears to be sufficient to prevent the protons from escaping the system during the acceleration. Confinement of electrons, on the other hand, requires the existence of plasma waves. Electrons can be accelerated to GeV energies through the process described here for solar flare conditions.