Combining MHD and kinetic modelling of solar flares

TL;DR

This paper reviews approaches that combine magnetohydrodynamic and kinetic models to better understand the complex processes of solar flares, focusing on bridging the gap between fluid and particle-based simulations.

Contribution

It discusses combined MHD/test-particle and hybrid fluid-kinetic models as new methods for simulating solar flares more accurately.

Findings

MHDTP models effectively simulate magnetic reconnection and particle acceleration.

Hybrid models enable the study of stronger flares with more energetic particles.

A novel reduced-kinetic model improves particle transport simulations.

Abstract

Solar flares are explosive events in the solar corona, representing fast conversion of magnetic energy into thermal and kinetic energy, and hence radiation, due to magnetic reconnection. Modelling is essential for understanding and predicting these events. However, self-consistent modelling is extremely difficult due to the vast spatial and temporal scale separation between processes involving thermal plasma (normally considered using magnetohydrodynamic (MHD) approach) and non-thermal plasma (requiring a kinetic approach). In this mini-review we consider different approaches aimed at bridging the gap between fluid and kinetic modelling of solar flares. Two types of approaches are discussed: combined MHD/test-particle (MHDTP) models, which can be used for modelling the flaring corona with relatively small numbers of energetic particles, and hybrid fluid-kinetic methods, which can be used for modelling stronger events with higher numbers of energetic particles. Two specific examples are discussed in more detail: MHDTP models of magnetic reconnection and particle acceleration in kink-unstable twisted coronal loops, and a novel reduced-kinetic model of particle transport.