Thermodynamical Evolution of Supra-Arcade Downflows

Abstract

Supra-arcade downflows (SADs) are dark, teardrop-shaped features descending upon flare arcades. They are thought to be the results of magnetic reconnection, but the detailed formation mechanism of SADs and their relationship to flare energy release are still unclear. In this work, we explore the thermodynamical properties of SADs in the 2011 October 22 limb flare using the observations of the Solar Dynamics Observatory/Atmospheric Imaging Assembly and an improved Differential Emission Measure (DEM) technique. Different heating events around SADs are identified and the propagation speeds of plasma heating are calculated. The first heating event starts with the increase of the emission measure at temperatures higher than 5 MK, about 2.8 minutes before the arrival of the first studied SAD. Its propagation speed is about 140 km/s, a little faster than the speed of the SAD. However, the other two events have fast propagation speeds more than 700 km/s. We suspect that the first heating event can be explained by adiabatic compression, but the others may have different causes. Besides, we observed that SADs can push away their surrounding spikes. The formation of SADs is further explained on the basis of patchy and bursty magnetic reconnection that reconnection outflows may push away surrounding plasma and leave dark lanes behind them. The reliability of the DEM results, heating and cooling mechanisms, and other SAD explanations are discussed.

15 pages, 8 figures, accepted for publication in ApJ

References in corpus (7)

• Thermal Diagnostics with the Atmospheric Imaging Assembly onboard the Solar Dynamics Observatory: A Validated Method for Differential Emission Measure Inversions
• The Magnetic Rayleigh-Taylor Instability in Three Dimensions
• An exploration of heating mechanisms in a supra-arcade plasma sheet formed after a coronal mass ejection
• Secondary Rayleigh-Taylor type Instabilities in the Reconnection Exhaust Jet as a Mechanism for Supra-Arcade Downflows
• Exploring Plasma Heating in the Current Sheet Region in a Three-Dimensional Coronal Mass Ejection Simulation
• Thermodynamics of supra-arcade downflows in solar flares
• Observation of Magnetic reconnection at a 3D null point associated with a solar eruption

Cited by in corpus (5)

• Coronal microjets in quiet-Sun regions observed with the Extreme Ultraviolet Imager onboard Solar Orbiter
• Plasma Heating Induced by Tadpole-Like Downflows in the Flaring Solar Corona
• Thermodynamic Evolution of Solar Flare Supra-arcade Downflows
• Investigation on the Spatiotemporal Structures of Supra-Arcade Spikes
• Saddle-shaped solar flare arcades