Broadening of the DEM by multi-shelled and turbulent loops

TL;DR

This study investigates whether turbulent, wave-driven solar coronal loops can produce broad differential emission measure (DEM) distributions, suggesting turbulence as an alternative explanation to multi-stranded loops for observed multi-thermal plasma.

Contribution

It demonstrates that turbulent mixing in impulsively excited loop models can produce broad DEMs, providing a new perspective on coronal plasma thermal structure.

Findings

Turbulent loop models broaden their initial DEMs due to mixing.

Continuously driven models produce DEMs comparable to observations.

DEM width depends on initial temperature contrast with the exterior.

Abstract

Broad differential emission measure (DEM) distributions in the corona are a sign of multi-thermal plasma along the line-of-sight. Traditionally, this is interpreted as evidence of multi-stranded loops. Recently, however, it has been shown that multi-stranded loops are unlikely to exist in the solar corona, because of their instability to transverse perturbations. We aim to test if loop models subject to the Transverse Wave-Induced Kelvin-Helmholtz (TWIKH) instability result in broad DEMs, potentially explaining the observations. We took simulation snapshots and compute the numerical DEM. Moreover, we performed forward-modelling in the relevant AIA channels before reconstructing the DEM. We find that turbulent loop models broaden their initial DEM, because of the turbulent mixing. The width of the DEM is determined by the initial temperature contrast with the exterior. We conclude that impulsively excited loop models have a rather narrow DEM, but that continuously driven models result in broad DEMs that are comparable to the observations.