The differential emission measure of nested hot and cool magnetic loops

The physical conditions causing the appearance of the low brightness temperature regions at 37 and 22 GHz are discussed. The source radiation stems from free-free processes (bremsstrahlung), and passes through the transparent chromosphere and corona. The absorption occurs either in the prominences or in coronal condensations with physical parameters between those of prominences and corona. A deficit in emission of the chromosphere-corona transition region in the vicinity of the inversion lines of the longitudinal component of the photospheric magnetic field could also result in the appearance of low temperature region.