An MHD avalanche model of multi-threaded coronal loop

TL;DR

This paper demonstrates through 3D MHD simulations that a single unstable thread in a multi-threaded coronal loop can trigger an avalanche, leading to energy release resembling nanoflares, with implications for coronal heating.

Contribution

First demonstration of an MHD avalanche in a multi-threaded coronal loop using 3D simulations, showing how one unstable thread can trigger widespread disruption.

Findings

An unstable thread can initiate an avalanche affecting multiple threads.

Energy release occurs in discrete bursts similar to nanoflares.

The process provides a potential trigger mechanism for coronal heating.

Abstract

For the first time, we demonstrate how an MHD avalanche might occur in a multi-threaded coronal loop. Considering 23 non-potential magnetic threads within a loop, we use 3D MHD simulations to show that only one thread needs to be unstable in order to start an avalanche even when the others are below marginal stability. This has significant implications for coronal heating in that it provides for energy dissipation with a trigger mechanism. The instability of the unstable thread follows the evolution determined in many earlier investigations. However, once one stable thread is disrupted, it coalesces with a neighbouring thread and this process disrupts other nearby threads. Coalescence with these disrupted threads then occurs leading to the disruption of yet more threads as the avalanche develops. Magnetic energy is released in discrete bursts as the surrounding stable threads are disrupted. The volume integrated heating, as a function of time, shows short spikes suggesting that the temporal form of the heating is more like that of \textit{nanoflares} than of constant heating.