TEMPERATURE STRUCTURE OF ACTIVE REGIONS DEDUCED FROM THE HELIUM-LIKE SULFUR LINES

Solar active-region temperatures have been determined from the full-Su n spectra of heliumlike sulphur (S XV) observed by the Bragg Crystal S pectrometer on board the Yohkoh satellite. The average temperature ded uced from S XV is demonstrated to vary with the solar activity level: A temperature of 2.5 x 10(6) K is derived from the spectra taken durin g low solar activity, similar to the general corona, while 4 x 10(6) K is obtained during a higher activity phase. For the latter, the high- temperature tail of the differential emission measure of active region s is found most likely due to the superposition of numerous flare-like events (micro/nano-flares).