Observational Signatures of Coronal Heating in MHD Simulations Without Radiation or a Lower Atmosphere

TL;DR

This study introduces a simple post-processing method to predict coronal emission in MHD simulations without radiation or lower atmosphere effects, revealing short-term brightenings and properties consistent with observed coronal loops.

Contribution

A novel approximate method for including missing effects in MHD simulations, enabling better predictions of coronal emission features without complex modeling.

Findings

Short-term brightenings in magnetic strands observed in simulations.

Simulated loop properties match observed width, lifetime, and shape.

Supports the idea of multi-stranded loops heated by nanoflare storms.

Abstract

It is extremely difficult to simulate the details of coronal heating and also make meaningful predictions of the emitted radiation. Thus, testing realistic models with observations is a major challenge. Observational signatures of coronal heating depend crucially on radiation, thermal conduction, and the exchange of mass and energy with the transition region and chromosphere below. Many magnetohydrodynamic simulation studies do not include these effects, opting instead to devote computational resources to the magnetic aspects of the problem. We have developed a simple method of accounting approximately for the missing effects. It is applied to the simulation output post facto and therefore may be a valuable tool for many studies. We have used it to predict the emission from a model corona that is driven by vortical boundary motions meant to represent photospheric convection. We find that individual magnetic strands experience short-term brightenings, both scattered throughout the computational volume and in localized clusters. The former may explain the diffuse component of the observed corona, while the latter may explain bright coronal loops. Several observed properties of loops are reproduced reasonably well: width, lifetime, and quasi-circular cross-section (aspect ratio not large). Our results lend support to the idea that loops are multi-stranded structures heated by "storms" of nanoflares.