Turbulent cross-field transport of non-thermal electrons in coronal loops: theory and observations

TL;DR

This paper combines theoretical models and observations from RHESSI to analyze how magnetic turbulence influences the cross-field transport of non-thermal electrons in coronal loops, providing insights into magnetic field fluctuations during solar flares.

Contribution

It develops a comprehensive framework linking magnetic turbulence regimes with observational data to estimate magnetic field line diffusion in solar coronal loops.

Findings

Magnetic fluctuations of about 1% of the background field are inferred from X-ray data.

The study constrains correlation lengths and Kubo numbers relevant to turbulence regimes.

A unified approach to interpret hard X-ray imaging data in the context of magnetic turbulence.

Abstract

A fundamental problem in astrophysics is the interaction between magnetic turbulence and charged particles. It is now possible to use \emph{Ramaty High Energy Solar Spectroscopic Imager (RHESSI)} observations of hard X-rays (HXR) emitted by electrons to identify the presence of turbulence and to estimate the magnitude of the magnetic field line diffusion coefficient at least in dense coronal flaring loops.} {We discuss the various possible regimes of cross-field transport of non-thermal electrons resulting from broadband magnetic turbulence in coronal loops. The importance of the Kubo number $K$ as a governing parameter is emphasized and results applicable in both the large and small Kubo number limits are collected.} {Generic models, based on concepts and insights developed in the statistical theory of transport, are applied to the coronal loops and to the interpretation of hard X-ray imaging data in solar flares. The role of trapping effects, which become important in the non-linear regime of transport, is taken into account in the interpretation of the data.} For this flaring solar loop, we constrain the ranges of parallel and perpendicular correlation lengths of turbulent magnetic fields and possible Kubo numbers. We show that a substantial amount of magnetic fluctuations with energy $\sim 1%$ (or more) of the background field can be inferred from the measurements of the magnetic diffusion coefficient inside thick-target coronal loops.