Numerical simulation of the internal plasma dynamics of post-flare loops

TL;DR

This paper uses numerical MHD simulations to model plasma dynamics in post-flare loops, reproducing observed features and suggesting shock waves explain certain flows and pulsations during flaring events.

Contribution

It introduces a finite-volume TVD scheme for 1D/2D MHD simulations of post-flare loops, providing new insights into plasma flows and quasi-periodic pulsations.

Findings

Simulated brightening features match observations.

Downflows are better explained as shock waves.

Reproduced quasi-periodic pulsations with time-dependent forcing.

Abstract

We integrate the MHD ideal equations of a slender flux tube to simulate the internal plasma dynamics of coronal post-flare loops. We study the onset and evolution of the internal plasma instability to compare with observations and to gain insight into physical processes and characteristic parameters associated with flaring events. The numerical approach uses a finite-volume Harten-Yee TVD scheme to integrate the 1D1/2 MHD equations specially designed to capture supersonic flow discontinuities. We could reproduce the observational sliding down and upwardly propagating of brightening features along magnetic threads of an event occurred on October 1st, 2001. We show that high--speed downflow perturbations, usually interpreted as slow magnetoacoustic waves, could be better interpreted as slow magnetoacoustic shock waves. This result was obtained considering adiabaticity in the energy balance equation. However, a time--dependent forcing from the basis is needed to reproduce the reiteration of the event which resembles observational patterns -commonly known as quasi--periodic pulsations (QPPs)- which are related with large scale characteristic longitudes of coherence. This result reinforces the interpretation that the QPPs are a response to the pulsational flaring activity.