Helicity-conserving relaxation in unstable and merging magnetic flux ropes

TL;DR

This paper investigates how helicity-conserving relaxation processes in magnetic flux ropes explain energy release in solar flares and flux rope mergers, supported by simulations and theoretical models.

Contribution

It extends relaxation theory to realistic coronal loop models and demonstrates its application to solar flare phenomena and flux rope interactions.

Findings

Helicity-conserving relaxation explains confined solar flares.

Simulations predict observational signatures of flares.

Flux rope mergers release magnetic energy via relaxation processes.

Abstract

Twisted magnetic flux ropes are reservoirs of free magnetic energy. In a highly-conducting plasma such as the solar corona, energy release through multiple magnetic reconnections can be modelled as a helicity-conserving relaxation to a minimum energy state. One possible trigger for this relaxation is the ideal kink instability in a twisted flux rope. We show that this provides a good description for confined solar flares, and develop from idealised cylindrical models to realistic models of coronal loops. Using 3D magnetohydrodynamic simulations combined with test-particle simulations of non-thermal electrons and ions, we predict multiple observational signatures of such flares. We then show how interactions and mergers of flux ropes can release free magnetic energy, using relaxation theory to complement simulations of merging-compression formation in spherical tokamaks and heating avalanches in the solar corona.