3D MHD simulation of flare supra-arcade downflows in a turbulent current sheet medium

TL;DR

This study uses 3D MHD simulations to explore the formation of supra-arcade downflows (SADs) in turbulent current sheets, highlighting the need for local energy deposition to produce observable SAD structures.

Contribution

It demonstrates that SAD cavities are formed through a combination of tearing and Kelvin-Helmholtz instabilities, requiring local energy input for realistic structures.

Findings

SADs require local energy deposition from reconnection events.

A relation exists between SAD sizes and current sheet widths.

Turbulent current sheets can produce SAD-like structures under certain conditions.

Abstract

Supra-arcade downflows (SADs) are sunward, generally dark, plasma density depletions originated above posteruption flare arcades. In this paper using 3D MHD simulations we investigate if the SAD cavities can be produced by a direct combination of the tearing mode and Kelvin-Helmholtz instabilities leading to a turbulent current sheet (CS) medium or if the current sheet is merely the background where SADs are produced triggered by an impulsive deposition of energy. We find that to give account of the observational dark lane structures an addition of local energy, provided by a reconnection event, is required. We suggest that there may be a closed relation between characteristic SAD sizes and CS widths that must be satisfied to obtain an observable SAD.