Sites of hot thermal plasma in solar flares Original Research Article

The time evolution of the emission measure derived from the Bragg Crystal Spectrometer (Fe xxv channel) and from the Soft X-ray Telescope images for 27 limb flares well-observed by Yohkoh has been compared. The ratio q of these two emission measures has been used as an estimation of relative contribution of hot thermal plasma. It has been confirmed that hot plasma is situated mainly inside the bright loop-top kernels, where it co-exists with cooler plasma. The maximal relative contribution qmax of hot plasma in kernels is larger for lower-situated events, which suggests a dependence on the amount of released energy. A method checking how well the bright loop-top kernel represents the site of hot thermal plasma has been proposed.