Isolating the Footpoint Characteristics of a Solar Flare Loop

Abstract

We analyse the physical characteristics of a C5.7 class flare which was observed on 27 September, 1993 using data from the soft X-ray telescope (SXT), the Bragg crystal spectrometer (BCS), and the hard X-ray telescope (HXT) on Yohkoh. The flare takes the form of a simple loop which 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-ray fluxes, and a corresponding peak in hard X-rays. The parameters derived 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-thermal velocity, the first one simultaneous with the footpoint brightening. The non-thermal velocity corresponding to these first few minutes is unusually large – by a factor of 80%, 68%, and 26% relative to the second peak in the Fexxv, Caxix, and Sxv channels respectively.