Time-dependent Turbulent Electron Acceleration and Transport in Solar Flares

TL;DR

This paper models time-dependent turbulent electron acceleration in solar flares using a Fokker-Planck approach, revealing how different acceleration profiles influence electron flux and X-ray emissions across energy bands.

Contribution

It introduces a novel time-dependent modeling framework for electron acceleration in solar flares, capturing transient effects and energy-dependent response times.

Findings

Acceleration source signature persists across energy bands.

Response time varies with energy, longer at higher energies.

Different input functions produce distinct temporal behaviors.

Abstract

Solar flares are explosive releases of magnetic energy stored in the solar corona, driven by magnetic reconnection. These events accelerate electrons, generating hard X-ray emissions and often display Quasi Periodic Pulsations (QPPs) across the energy spectra. However, the energy transfer process remains poorly constrained, with competing theories proposing different acceleration mechanisms. We investigate electron acceleration and transport in a flaring coronal loop by solving a time-dependent Fokker-Planck equation. Our model incorporates transient turbulent acceleration, simulating the effects of impulsive energy input to emulate the dynamics of time-dependent reconnection processes. We compute the density-weighted electron flux, a diagnostic directly comparable to observed X-ray emissions, across the energy and spatial domains from the corona to the chromosphere. We investigate different time-dependent functional forms of the turbulent acceleration, finding that the functional form of the acceleration source maintains its signature across energy bands (1 to 100 keV) with a response time that is energy dependent (with higher energy bands displaying a longer response time). In addition, we find that (a) for a square pulse the switch on and off response time is different; (b) for a sinusoidal input the periodicity is preserved; and (c) for a damped sinusoidal the decay rate increases with density and higher energy bands lose energy faster. This work presents a novel methodology for analyzing electron acceleration and transport in flares driven by time-dependent sources.