Joint Observations of Terrestrial Gamma-ray Flashes and Transient Luminous Events with RHESSI and ISUAL

One of the many outstanding questions about Terrestrial Gamma-ray Flashes (TGFs) is whether they are usually -- or ever -- associated with Transient Luminous Events (TLEs) such as sprites and elves. Models of relativistic runaway in a strong DC field might suggest the former, and runaway models invoking strong transient (EMP) fields the latter. We will present preliminary results of a search for simultaneous detection of TGFs and TLEs using data from spots simultaneously covered by the RHESSI satellite (measuring gamma-ray flashes at its subsatellite point) and the ISUAL instrument on FORMOSAT-2 (measuring luminous events from its horizon).