Photospheric magnetic field changes associated with transition region explosive events

From a comparison of the Solar and Heliospheric Observatory SUMER spectral 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 interior of strong magnetic flux concentrations but rather are preferentially found in regions with weak and mixed polarity fluxes that display magnetic neutral lines. Second, the majority of explosive events happen 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 decreases because of cancellation. These results strongly support the idea that transition region explosive events are a manifestation of magnetic reconnection occurring in the quiet Sun. Furthermore, one may infer from the third result that the explosive events represent repetitive fast magnetic reconnections in the transition region, which are initiated by slow magnetic reconnections occurring beneath.