Simulation of dark lanes in post--flare supra--arcades

TL;DR

This paper uses 1.5D and 2D simulations to reproduce and analyze dark lanes in post-flare supra-arcades, explaining them as hot plasma vacuums formed by slow magnetoacoustic shocks, and explores their behavior relative to magnetic field strength.

Contribution

First 2D simulation results confirm and extend previous 1D models, showing the influence of magnetic field on plasma dynamics and void formation in post-flare regions.

Findings

Dark lanes are explained as hot plasma vacuums generated by shocks.

In 2D, the period of kink-like structures depends on magnetic field strength.

Sunward speed increases with magnetic field strength in 2D simulations.

Abstract

Using two simulations of 1.5D, for the first time, in Costa et al. (2009) and Shulz et al. (2010) we numerically reproduce the observational dark inflows described in Verwichte et al. (2005). We show that the dark tracks can be explained as hot plasma vacuums generated upstream of a slow magnetoacoustic shock wave produced by a localized deposition of energy. In this work, we show that the overall 2D results are in agreement with the observational behaviour. However they show a slight shift in the characteristic parameter with respect to those found previously. Also, we confirm qualitatively the behaviour found in the previous papers, i.e. for a given numerical domain the period of the kink--like structure is a function of the magnetic field intensity: larger periods are associated with lower magnetic field intensities. Contrary to the 1D result -where the sunward dynamic is independent of the magnetic field intensity due to its exclusively waveguide role- in the 2D simulation the sunward speed is larger for larger values of the magnetic field. This can be interpreted as the capability of the low coronal plasma to collimate the deposition of energy into the magnetic field direction. The moving features consistent of low--density and high--temperature plasma cavities have larger inside values of the structuring parameter beta than the neighboring media. Thus, the voids seem to be the emergence structures of a whole nonlinear interacting plasma context of shocks and waves more than voided plasma loops magnetically structured.