Constraining turbulent solar flare acceleration regions by connecting kinetic modeling and X-ray observations

TL;DR

This study integrates kinetic modeling with X-ray observations to constrain the properties of turbulence-driven electron acceleration in solar flares, revealing large acceleration regions and specific timescales.

Contribution

It is the first to connect inhomogeneous turbulence acceleration with X-ray data and kinetic models to constrain flare acceleration properties.

Findings

Extended turbulence regions (~25% of flare loop) are necessary for matching X-ray data.

Acceleration timescales range from 7 to 22 seconds, aiding model constraints.

Large-scale turbulence is crucial for efficient electron acceleration in flares.

Abstract

Spatially-resolved X-ray observations are the key to understanding electron acceleration in solar flares. Currently, the underlying processes that efficiently energize solar flare particles are poorly constrained. Abundant flare observations suggest that turbulence plays a crucial role in transferring energy between the magnetic field and energetic electrons. For the first time, we connect inhomogeneous acceleration from turbulence and hard X-ray spectroscopy and imaging observations with kinetic modeling to constrain the properties of flare acceleration. Observing three large flares with RHESSI, or Solar Orbiter/STIX, we extract X-ray imaging and spectroscopy observables. We compare with modeling results, mapping observables to electron acceleration and turbulent properties. We determine that extended regions of turbulence are required to match multiple X-ray observables, suggesting electrons are accelerated over a large fraction (~25%) of the flare loop; a property that is usually unconstrained from X-ray observations alone. Additionally, we determine acceleration timescales that vary between 7 and 22s by using fixed values for the turbulent scattering timescale and the velocity dependence of the acceleration diffusion coefficient. These fixed values are effectively unconstrained, but yield acceleration timescales that will help to restrict possible viable stochastic models.