Temperatures of pre-flare and flaring loops observed with the Yohkoh soft X-ray telescope

Abstract We statistically investigate thermal characteristics of soft X-ray coronal loops in the pre-flare and flaring stages using the data observed between January 1992 and December 1992 with the soft X-ray telescope on board the Yohkoh satellite. The data cover the pre-flare phase in the periods of 30–90 minutes preceding the flares, the rising phases, and the peaks of flares in X-ray intensity, and the beginnings of the decay phases. We compare the thermal characteristics of soft X-ray coronal loops before they flare and those at the peaks of flares, and we find that the loops having higher temperatures in the pre-flare stages produce bigger and higher temperature flares later.