YOHKOH SXT HXT OBSERVATIONS OF A 2-LOOP INTERACTION SOLAR-FLARE ON 1992 DECEMBER 9/

Observations with the Soft X-ray and Hard X-ray Telescopes aboard Yohk oh of a simple solar flare on 1992 December 9 are discussed. The soft X-ray morphology suggests evidence of a loop-loop interaction mechanis m: the images reveal two parallel magnetic loops prior to the flare, a nd their merging just before onset of the hard X-ray burst. This flare therefore provides a chance to examine the two-loop interaction model for solar flares. It is found (1) that the observed soft X-ray behavi or of the two loops in the preflare phase well matches to the two-loop interaction model between strong and weak current loops and (2) that the observed time scale of the two-loop coalescence is almost equal to that estimated from explosive-reconnection theory. In the impulsive p hase, it is found (3) that the loop-top portion near to the interactio n region first brightens in the 14-23 keV hard X-rays and (4) that the 23-33 keV hard X-ray emission around the peak time originates dominan tly from two compact sources at the two ends of the merging loops. The se hard X-ray observations are explained by high-energy electrons that are produced in the two current loop interaction.