摘要
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 looplike 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.
基金
The authors thank the SDO,GOES,and RHESSI teams for providing the data,and Shinsuke Takasao for helpful discussion.This work was supported by NSFC grants 11825301 and 11790304,Strategic Priority Research Program of CAS(grant XDA17040507)
NASA LWS grant 80NSSC19K0069,NSF grants AST-1735405 and AGS-1723436 to New Jersey Institute of Technology(NJIT)
NASA grant 80NSSC18K0732 and NASA's SDO/AIA contract(NNG04EA00C)to the Lockheed Martin Solar and Astrophysics Laboratory.AIA is an instrument onboard the SDO,a mission for NASA's Living With a Star program.
