Energy release in driven twisted coronal loops

TL;DR

This study explores how magnetic field topology and thermodynamic effects influence energy release during kink instabilities in twisted coronal loops, revealing the roles of footpoint convergence, curvature, and atmospheric stratification.

Contribution

It systematically analyzes the impact of field topology and thermodynamics on energy release in driven twisted coronal loops, highlighting stabilizing and destabilizing factors.

Findings

Footpoint convergence stabilizes loops, requiring more energy for instability.

Large-scale curvature reduces the energy released during instability.

Stratified atmospheres induce decaying wave phenomena and decrease loop stability.

Abstract

In the present study we investigate magnetic reconnection in twisted magnetic fluxtubes with different initial configurations. In all considered cases, energy release is triggered by the ideal kink instability, which is itself the result of applying footpoint rotation to an initially potential field. The main goal of this work is to establish the influence of the field topology and various thermodynamic effects on the energy release process. Specifically, we investigate convergence of the magnetic field at the loop footpoints, atmospheric stratification, as well as thermal conduction. In all cases, the application of vortical driving at the footpoints of an initally potential field leads to an internal kink instability. With the exception of the curved loop with high footpoint convergence, the global geometry of the loop change little during the simulation. Footpoint convergence, curvature and atmospheric structure clearly influences the rapidity with which a loop achieves instability as well as the size of the subsequent energy release. Footpoint convergence has a stabilising influence and thus the loop requires more energy for instability, which means that the subsequent relaxation has a larger heating effect. Large-scale curvature has the opposite result: less energy is needed for instability and so the amount of energy released from the field is reduced. Introducing a stratified atmosphere gives rise to decaying wave phenomena during the driving phase, and also results in a loop that is less stable.