Temporal and spatial relationships between ultraviolet and hard X-ray emission in solar flares

Hard X-ray and ultraviolet emissions in solar flares provide evidence for the interaction of particles accelerated in the solar corona with the ambient plasma in the chromosphere. Previous studies have shown that these emissions are temporally correlated indicating a common source, presumably magnetic reconnection, governing the flare energy release. We use the high spatial resolution of the RHESSI and TRACE telescopes to explore the temporal connections of spatially resolved hard X-ray and UV sources in a flare occurring on 2002 July 16. While exhibiting a strong temporal correlation, there are distinct differences in the spatial distribution of the UV and hard X-ray emissions. The UV emission is found to be distributed in two well-defined ribbons spanning 50" - 100" and separated by some 50" - 70", while the hard X-ray emission is localized to a compact distribution at one end of the southernmost ribbon. We argue that the temporally correlated, but spatially well-separated, emissions result from the interaction of an evolving multipolar magnetic flux system with the flare energy release predominantly occurring along a separator marking the intersection of separate topological domains defined by an emerging bipolar system and the preexisting active region magnetic field.