Plasma heating and nanoflare caused by slow-mode wave in a coronal loop

TL;DR

This study analyzes a slow magnetoacoustic wave in a coronal loop triggered by a microflare, demonstrating wave reflection, damping mechanisms, and a wave-induced nanoflare, offering insights into coronal heating processes.

Contribution

It provides the first solid evidence of a wave-induced nanoflare caused by a slow-mode wave in a coronal loop, linking wave dynamics to nanoflare heating.

Findings

The wave propagates at the local sound speed consistent with a slow magnetoacoustic wave.

Thermal conduction is the main damping mechanism, with additional damping needed.

A nanoflare with energy around 10^{24}-10^{25} erg is produced at the remote footpoint.

Abstract

We present a detailed analysis of a reflecting intensity perturbation in a large coronal loop that appeared as sloshing oscillation and lasted for at least one and a half periods. The perturbation is initiated by a microflare at one footpoint of the loop, propagates along the loop and is eventually reflected at the remote footpoint where significant brightenings are observed in all the AIA extreme-ultraviolet (EUV) channels. This unique observation provides us with the opportunity to better understand not only the thermal properties and damping mechanisms of the sloshing oscillation, but also the energy transfer at the remote footpoint. Based on differential emission measures (DEM) analysis and the technique of coronal seismology, we find that 1) the calculated local sound speed is consistent with the observed propagation speed of the perturbation during the oscillation, which is suggestive of a slow magnetoacoustic wave; 2) thermal conduction is the major damping mechanism of the wave but additional damping mechanism such as anomalous enhancement of compressive viscosity or wave leakage is also required to account for the rapid decay of the observed waves; 3) the wave produced a nanoflare at the remote footpoint, with a peak thermal energy of $\thicksim10^{24}-10^{25}$ erg. This work provides a consistent picture of the magnetoacoustic wave propagation and reflection in a coronal loop, and reports the first solid evidence of a wave-induced nanoflare. The results reveal new clues for further simulation studies and may help solving the coronal heating problem.