MICROWAVE AND HARD X-RAY OBSERVATIONS OF FOOTPOINT EMISSION FROM SOLAR-FLARES

We investigate radio and X-ray imaging data for two solar hares in ord er to test the idea that asymmetric precipitation of nonthermal electr ons at the two ends of a magnetic loop is consistent with the magnetic -mirroring explanation. The events we present were observed in 1993 Ma y by the HXT and SXT X-ray telescopes on the Yohkoh spacecraft and by the Nobeyama 17 GHz radioheliograph. The hard X-ray images in one case show two well-separated sources; the radio images indicate circularly polarized, nonthermal radio emission with opposite polarities from th ese two sources, indicating oppositely directed fields and consistent with a single-loop model. In the second event there are several source s in the HXT images which appear to be connected by soft X-ray loops. The strongest hard X-ray source has unpolarized radio emission, wherea s the strongest radio emission lies over strong magnetic fields and is polarized. In both events the strongest radio emission is highly pola rized and not coincident with the strongest hard X-ray emission. This is consistent with asymmetric loops in which the bulk of the precipita tion (and hence the X-ray emission) occurs at the weaker field footpoi nt.