fl243.raulin01 Posted: 16-Dec-96 Updated: Events specified: see text
J.P. Raulin, V. Makhmutov, P. Kaufmann, J.E.R Costa, G. Gimenez de Castro and H. Hudson
e-mail: raulin@nucate.unicamp.br
Millimeter radio emission in flares is produced by the highest energy (MeV) electrons accelerated by solar flares. At these frequencies the gyrosynchrotron spectrum is generally optically thin, which makes it very suitable to study the temporal evolution of the electron population during the impulsive phase of flares. Moreover the combination of hard X-ray and millimeter flare emissions allows to know if whether both emission come from the same population of accelerated electrons, which is fundamental to test existing flare models. We have observed 4 flares with the Itapetinga radio antenna at 48 GHz with high spatial resolution (few arcsec), high time resolution (1 ms), and high sensitivity (0.05 sfu). For these events we already got ground based radio (RSTN) and optical (KPNO magnetograms, H alpha, white-ht) observations. A preliminary study seems to indicate the presence of time fluctuations on timescales of a few seconds as well as few hundred of millisecond, during the impulsive phase. It is also clear that the impulsive millimeter emission is composed of several components separated in space by few arcsec. We would like to combine our data set with hard X-ray emission observed by HXT (Yohkoh), in order to study the temporal and spatial evolution of the different emissions during the impulsive phase, and constraint the existing flare models.
Itapetinga events:
Date Starting time Active Region
25 June 1992 17:51 UT AR 7205
20 August 1992 14:26 UT AR 7260
17:21 UT AR 7260
28 October 1992 10:10 UT AR 7231
11 February 1993 18:31 UT AR 7421