Fine structure of a solar flare region at 3.7 and 11.1 cm wavelengths

Abstract

On June 9, 1973, a flare associated burst was observed with the NRAO 3-element interferometer at 3.7 and 11.1 cm wavelength. The burst was of ‘gradual rise and fall’ type. Comparing the fringe amplitudes at 3.7 cm to the visibility computed for model flare regions we found that the precursor data are best fitted by a region of 3″ in size while at the time of the peak, the flare appears to have a size of 2″. During the post-maximum phase a size of 5″ is the best estimate. Similar computations have been done for 11.1 cm data. The peak brightness temperatures are 1.2 × 10⁹ K and 1.65 × 10⁸ K at 3.7 and 11.1 cm respectively. Such high temperatures would imply that a significant fraction of the burst radiation has a non-thermal origin.