PHOTOSPHERIC MAGNETIC-FIELD CHANGES ASSOCIATED WITH TRANSITION REGIONEXPLOSIVE EVENTS

From a comparison of the Solar and Heliospheric Observatory SUMER spec tral data and a time series of Big Bear Solar Observatory magnetograms , we present observational clues to the physical origin of transition region explosive events. First, explosive events rarely occur in the i nterior of strong magnetic flux concentrations but rather are preferen tially found in regions with weak and mixed polarity fluxes that displ ay magnetic neutral lines. Second, the majority of explosive events ha ppen during the ''cancellation'' of photospheric magnetic flux. Third, there is a strong tendency for explosive events to occur repeatedly, as bursts, while local photospheric magnetic flux continuously decreas es because of cancellation. These results strongly support the idea th at transition region explosive events are a manifestation of magnetic reconnection occurring in the quiet Sun. Furthermore, one may infer fr om the third result that the explosive events represent repetitive fas t magnetic reconnections in the transition region, which are initiated by slow magnetic reconnections occurring beneath.