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

Tanmoy Samanta,Hui Tian,Bin Chen,Katharine K Reeves,Mark C.M Cheung,Angelos Vourlidas,Dipankar Banerjee

doi:10.1016/j.xinn.2021.100083

Abstract

SummaryAs 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.

Highlights

Solar flares are characterized by a sudden enhancement of the electromagnetic radiation in a broad range of wavelengths on the Sun.[1]
Flares are generally believed to result from magnetic reconnection, a physical process referring to the re-arrangement of the magnetic field topology in a plasma
We witnessed numerous downward-propagating supra-arcade downflows (SADs) in the supra-arcade fan above the flare loops during the decay phase of the flare

Summary

Introduction

Solar flares are characterized by a sudden enhancement of the electromagnetic radiation in a broad range of wavelengths on the Sun.[1] They are believed to be one of the dominant sources of severe disturbances in the space environments of the Earth and other planets in the solar system. Flares are generally believed to result from magnetic reconnection, a physical process referring to the re-arrangement of the magnetic field topology in a plasma. The free magnetic energy is released and converted into kinetic and thermal energies.[1] As a result of the re-arrangement of the magnetic field topology, a series of new loop-like magnetic structures called flare loops are often formed below the reconnection site. A hot diffuse region, consisting of plasma with a temperature of around 5–10 MK, is observed above the loops and is called a supra-arcade fan.[2,3,4]

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Conclusion