Can Multi-Threaded Flux Tubes in Coronal Arcades Support a Magnetohydrodynamic Avalanche?

TL;DR

This study uses 3D MHD simulations to explore how multi-threaded coronal loops in curved arcades can support magnetic instabilities and avalanches, revealing complex interactions influenced by geometry and driving speeds.

Contribution

It demonstrates the impact of multiple threads and realistic arcade geometry on the development of MHD instabilities and energy release in coronal loops, extending previous cylindrical models.

Findings

Single-thread loops destabilize via ideal MHD instabilities.

Multiple threads influence each other's destabilization.

Continuous driving causes secondary energetic bursts.

Abstract

Magnetohydrodynamic (MHD) instabilities allow energy to be released from stressed magnetic fields, commonly modelled in cylindrical flux tubes linking parallel planes, but, more recently, also in curved arcades containing flux tubes with both footpoints in the same photospheric plane. Uncurved cylindrical flux tubes containing multiple individual threads have been shown to be capable of sustaining an MHD avalanche, whereby a single unstable thread can destabilise many. We examine the properties of multi-threaded coronal loops, wherein each thread is created by photospheric driving in a realistic, curved coronal arcade structure (with both footpoints of each thread in the same plane). We use three-dimensional MHD simulations to study the evolution of single- and multi-threaded coronal loops, which become unstable and reconnect, while varying the driving velocity of individual threads. Experiments containing a single thread destabilise in a manner indicative of an ideal MHD instability and consistent with previous examples in the literature. The introduction of additional threads modifies this picture, with aspects of the model geometry and relative driving speeds of individual threads affecting the ability of any thread to destabilise others. In both single- and multi-threaded cases, continuous driving of the remnants of disrupted threads produces secondary, aperiodic bursts of energetic release.