THE MORPHOLOGY OF THE 10(7)-K PLASMA IN SOLAR-FLARES .1. NONIMPULSIVE FLARES

In this paper we have analyzed images of 48 C-, M-, and X-type flares which occurred between 1991 October and 1993 February. The images were recorded by the soft X-ray telescope (SXT) flown on the Japanese Yohkoh spacecraft. The spatial resolution of the recorded images is about 2.5''. In each of the recorded flares the brightest regions emitting the 10(7) K radiation were analyzed and evaluated. The 10(7) K emitting region was found to be located at loop tops in the first well-exposed flare image recorded during the rise phase (within 1-2 minutes after flare onset), in images recorded near intensity peak, and in those recorded during most of the decay phase. Occasionally, in the begining of the event when the total flare intensity is low, the brightness of the footpoints may rival the brightness of the loop top. However, in these cases it is expected that the temperature of the loop top is considerably higher. The emitting region, even during flare peak, is very small (often smaller than a single SXT pixel 1800 x 1800 km).