Plasma Heating Induced by Tadpole-Like Downflows in the Flaring Solar Corona

TL;DR

This paper reports on observations of tadpole-like downflows in solar flares that collide with flare loops, significantly heating the plasma and possibly explaining quasi-periodic pulsations in solar flare emissions.

Contribution

It provides new observational evidence linking supra-arcade downflows to plasma heating and pulsation phenomena in solar flares.

Findings

SADs collide with flare loops and heat plasma to 10-20 MK.

Interactions produce quasi-periodic soft X-ray emission enhancements.

Suggests SADs contribute to flare energy release and pulsations.

Abstract

As one of the most spectacular energy release events in the solar system, solar flares are generally powered by magnetic reconnection in the solar corona. As a result of the re-arrangement of magnetic field topology after the reconnection process, a series of new loop-like magnetic structures are often formed and are known as flare loops. A hot diffuse region, consisting of around 5-10 MK plasma, is also observed above the loops and is called a supra-arcade fan. Often, dark, tadpole-like structures are seen to descend through the bright supra-arcade fans. It remains unclear what role these so-called supra-arcade downflows (SADs) play in heating the flaring coronal plasma. Here we show a unique flare observation, where many SADs collide with the flare loops and strongly heat the loops to a temperature of 10-20 MK. Several of these interactions generate clear signatures of quasi-periodic enhancement in the full-Sun-integrated soft X-ray emission, providing an alternative interpretation for quasi-periodic pulsations that are commonly observed during solar and stellar flares.