Simulation of dark lanes in post-flare supra-arcade

COSTA, A., ELASKAR, S., FERNÁNDEZ, C., MARTÍNEZ, G.

MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY

Wiley Blackwell INterscience

Año: 2009 vol. 400 p. 85 - 90

0035-8711

We integrate the magnetohydrodynamics (MHD) ideal equations to simulate dark void sunwardly moving structures in post-flare supra-arcades. We study the onset and evolution ofthe internal plasma instability to compare with observations and to gain insight into physicalprocesses and characteristic parameters of these phenomena. The numerical approach uses afinite-volume Harten–Yee total variation diminishing (TVD) scheme to integrate the 1D 1/2MHD equations specially designed to capture supersonic flow discontinuities. The integrationis performed in both directions, the sunward radial one and the transverse to the magnetic field.For the first time, we numerically reproduce observational dark voids described in Verwichteet al. We show that the dark tracks are plasma vacuums generated by the bouncing and interfering of shocks and expansion waves, upstream an initial slow magnetoacoustic shock producedby a localized deposition of energy modeled with a pressure perturbation. The same pressureperturbation produces a transverse to the field or perpendicular magnetic shock giving rise tonon-linear waves that compose the kink-like plasma void structures, with the same functionalsunward decreasing phase speed and constancy with height of the period, as those determinedby the observations.