Direct observation of high-speed plasma outflows produced by magnetic reconnection in solar impulsive events

摘要

Spectroscopic observations of a solar limb flare recorded by SUMER on SOHOreveal, for the first time, hot fast magnetic reconnection outflows in thecorona. As the reconnection site rises across the SUMER spectrometer slit,significant blue- and red-shift signatures are observed in sequence in the FeXIX line, reflecting upflows and downflows of hot plasma jets, respectively.With the projection effect corrected, the measured outflow speed is between900-3500 km/s, consistent with theoretical predictions of the Alfvenic outflowsin magnetic reconnection region in solar impulsive events. Based on theoreticmodels, the magnetic field strength near the reconnection region is estimatedto be 19-37 Gauss.