A LOOP TOP HARD X-RAY SOURCE IN A COMPACT SOLAR-FLARE AS EVIDENCE FORMAGNETIC RECONNECTION

SOLAR flares are thought to be the result of magnetic reconnection-the merging of antiparallel magnetic fields and the consequent release of magnetic energy, Flares are classified into two types(1): compact and two-ribbon. The two-ribbon flares, which appear as slowly-developing, long-lived large loops, are understood theoretically(2-6) as arising from an eruption of a solar prominence that pulls magnetic field lines upward into the corona. As the field lines form an inverted Y-shaped structure and relax, the reconnection of the field lines takes place. This view has been supported by recent observations(7-10). A different mechanism seemed to be required, however, to produce the short-lived, impulsive compact flares. Here we report observations made with the Y ohkoh(11) Hard X-ray Telescope(12) and Soft X-ray Telescope(13), which show a compact flare with a geometry similar to that of a two-ribbon Bare. We identify the reconnection region as the site of particle acce leration, suggesting that the basic physics of the reconnection proces s (which remains uncertain) mag be common to both types of flare.