ISOLATING THE FOOTPOINT CHARACTERISTICS OF A SOLAR-FLARE LOOP

We analyse the physical characteristics of a C5.7 class flare which wa s observed on 27 September, 1993 using data from the soft X-ray telesc ope (SXT), the Bragg crystal spectrometer (BCS), and the hard X-ray te lescope (HXT) on Yohkoh. The flare takes the form of a simple loop whi ch is much brighter at one of its footpoints than anywhere else for a period of 2 min. During this time there is an increase in the soft X-r ay fluxes, and a corresponding peak in hard X-rays. The parameters der ived from the hard X-ray and soft X-ray spectra and images are assumed to be from the footpoint. This flare showed two peaks in the non-ther mal velocity, the first one simultaneous with the footpoint brightenin g. The non-thermal velocity corresponding to these first few minutes i s unusually large - by a factor of 80%, 68%, and 26% relative to the s econd peak in the Fe XXV, Ca XIX, and S XV channels respectively.