EVIDENCE FOR MAGNETIC RECONNECTION IN THREE HOMOLOGOUS SOLAR FLARES OBSERVED BY RHESSI

摘要

We present RHESSI observations of three homologous flares that occurred between 2002 April 14 and 16. We find that the RHESSI images of all three flares at energies between 6 and 25 keV had some common features: (1) A separate coronal source up to ～30″ above the flare loop appeared in the early impulsive phase and stayed stationary for several minutes. (2) Before the flare loop moved upward, as previously reported by others, the flare loop-top centroid moved downward for 2-4 minutes during the early impulsive phase of the flare, falling by 13%-30% of its initial height with a speed between 8 and 23 km s~(-1). We conclude that these features are associated with the formation and development of a current sheet between the loop top and the coronal source. In the 2002 April 14-15 flare, we find that the hard X-ray flux ( > 25 keV) is correlated with the rate at which the flare loop moves upward, indicating that the faster the loop grows, the faster the reconnection rate and therefore the greater the flux of accelerated electrons.