The thermal phase of a large solar flare

EUV and X-ray observations are used to derive the differential emission measures, temperatures, densities, radiative and conductive cooling rates, and thermal energy content of a class 2B flare that occurred on 1973 September 7. The results of the analysis indicate that (1) most of the flare plasma was at emperatures between 3 and 10 million degrees; (2) the peak temperature decreased with time from about 8 x 10/sup 6/ K to 5 x 10/sup 6/ K over a period of 3.5 hours; (3) the differential emission measure steadily decreased with time at nearly all temperatures; (4) both radiation and conduction were important cooling mechanisms for the plasma at T>10/sup 5/ K; and (5) a substantial amount of energy, of the order of 3 x 10/sup 31/ ergs, wa deposited in the flare loops after flare maximum. The empirically determined flare parameters are compaed with similar parameters derived from a simple theoretical loop model.