Observations of The Magnetic Reconnection Signature of An M2 Flare on 2000 March 23

摘要

Multi-wavelength observations of an M 2.0 flare event on 2000 March 23 inNOAA active region 8910 provide us a good chance to study the detailedstructure and dynamics of the magnetic reconnection region. In the process ofthe flare, extreme ultraviolet (EUV) loops displayed two times of sidewardmotions upon a loop-top hard X-ray source with average velocities of 75 and25.6 km/s, respectively. We consider these two motions to be the observationalevidence of reconnection inflow, and find an X-shaped structure upon thepost-flare loops during the period of the second motion. Two separations of theflare ribbons are associated with these two sideward motions, with averagevelocities of 3.3 and 1.3 km/s, separately. Using the observation ofphotospheric magnetic field, the velocities of the sideward motions and theseparations, we deduce the corresponding coronal magnetic field strength to beabout 13.2-15.2 G, and estimate the reconnection rates to be 0.05 and 0.02 forthese two magnetic reconnection processes, respectively. We also observemotions of bright points upward and downward along the EUV loops withvelocities ranging from 45.4 to 556.7 km/s. A cloud of bright material flowingoutward from the loop-top hard X-ray source with an average velocity of 51 km/sin the process of the flare may be accelerated by the tension force of thenewly reconnected magnetic field lines. All the observations can be explainedby schematic diagrams of magnetic reconnection.