An overview of flux braiding experiments

TL;DR

This paper reviews numerical simulations of magnetic flux braiding in the solar corona, highlighting the formation of thin current layers and their role in energy release, with implications for coronal heating.

Contribution

It provides a comprehensive overview of flux braiding experiments, emphasizing the formation of finite-thickness current layers and their significance in coronal energy dissipation.

Findings

Current layers tend to form with exponentially decreasing thickness.

The coronal volume reaches a statistically steady state with intermittent energy flux.

Magnetic braiding remains a promising but unconfirmed mechanism for coronal heating.

Abstract

Parker has hypothesised that, in a perfectly ideal environment, complex photospheric motions acting on a continuous magnetic field will result in the formation of tangential discontinuities corresponding to singular currents. We review direct numerical simulations of the problem and find the evidence points to a tendency for thin but finite thickness current layers to form, with thickness exponentially decreasing in time. Given a finite resistivity these layers will eventually become important and cause the dynamical process of energy release. Accordingly, a body of work focusses on evolution under continual boundary driving. The coronal volume evolves into a highly dynamic but statistically steady state where quantities have a temporally and spatially intermittent nature and where the Poynting flux and dissipation are decoupled on short timescales. Although magnetic braiding is found to be a promising coronal heating mechanism much work remains to determine its true viability. Some suggestions for future study are offered.