fl222.harra_murnion03 Posted: 26-Nov-95 Updated: Events specified: Flare of 27-Oct-93 10:48
L.K. Harra--Murnion^1, J. L. Culhane^1, H. S. Hudson^2, T. Fujiwara^3, T. Kato^4, and A. C. Sterling^5
^1 Mullard Space Science Laboratory, Holmbury St. Mary, Surrey, RH5 6NT,UK.
^2 Institute of Astronomy, University of Hawaii, Honolulu, HI 96822.
^3 Dept. of Education, Aichi University of Education, Igaya cho, Kariya, 448, Japan.
^4 National Institute of Fusion Plasma Science, Nagoya, Japan.
^5 Computational Physics Inc., 2750 Properity Avenue, Suite 600, Fairfax, VA 22031.
This work is related to the 2 pieces of work now in press, and published (Khan et al, ApJ Letters and Mariska et al ApJ) related to isolating the looptops of solar flares with BCS by the method of occultation. Specifically both papers concentrated on the values of the non-thermal velocity. For this work we analyse 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). In SXT the flare appears to take the form of a simple loop which is initially much brighter at one of its footpoints than anywhere else. At the time when most intense emission is coming from this footpoint, there is a corresponding increase in the BCS light curves, and a corresponding peak in hard X-rays. During the time of the footpoint brightening the parameters derived from the hard X-ray and soft X-ray spectra and images can be assumed to be from the footpoint. It was found that there were 2 peaks in the non-thermal velocity - the first one being consistent 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.