Temperature structure of the corona

Abstract

New aspects in the temperature structure of solar corona are briefly discussed mainly based on the observations obtained by Yohkoh. The dynamic behavior of the solar corona is recognizable in the temperature structures. Yohkoh has two instruments which are capable of diagnosing coronal plasmas in “non-flaring states”, namely SXT and BCS sulphur channel (SXV). The major characteristic of these two instruments is that they put more emphasis on looking at high-temperature components in the corona than the instruments flown in the Skylab era. Numerous tiny loop brightenings in active regions can be observed in the BCS sulphur channel as well as SXT and this flare-like activity (microflares) is responsible for producing the high-temperature part of the differential emission measure distribution in active regions. High- temperature loops seen in SXT/BCS and the coronal yellow line are spatially different from those seen in NIXT or the green/red lines and evolve differently. This also suggests that the high-temperature component comes from non-stationary activity. Coronal holes have plasmas having temperatures comparable to the quiet-sun, though the emission measure is very low.