On the complex nature of coronal heating

TL;DR

This study uses 3D resistive MHD simulations to explore the complex magnetic and plasma structures of coronal loops, revealing that they are not simple flux tubes but involve intricate interactions, heating, and reconnection processes.

Contribution

It demonstrates that coronal loops are structurally complex, involving dynamic magnetic interactions and cannot be accurately modeled as uniform flux tubes.

Findings

Bright structures are shaped by heating, cooling, and evaporation timescales.

Current sheets form at magnetic flux interfaces and within magnetic bundles.

Coronal loops exhibit features of both flux tube tectonics and flux braiding models.

Abstract

A large part of the hot corona consists of magnetically confined, bright plasma loops. These observed loops are in turn structured into bright strands. We investigate the relationship between magnetic field geometry, plasma properties and bright strands with the help of a 3D resistive MHD simulation of a coronal loop rooted in a self-consistent convection zone layer. We find that it is impossible to identify a loop as a simple coherent magnetic flux tube that coincides with plasma of nearly uniform temperature and density. The location of bright structures is determined by a complex interplay between heating, cooling and evaporation timescales. Current sheets form preferentially at the interfaces of magnetic flux from different sources. They may also form within bundles of magnetic field lines since motions within magnetic concentrations drive plasma flows on a range of timescales that provide further substructure and can locally enhance magnetic field gradients and thus facilitate magnetic reconnection. The numerical experiment therefore possesses aspects of both the flux tube tectonics and flux braiding models. While modelling an observed coronal loop as a cylindrical flux tube is useful to understand the physics of specific heating mechanisms in isolation, it does not describe well the structure of a coronal loop rooted in a self-consistently evolving convection zone.