Diagnostics of hot thermal plasma in flare-associated x-ray ejections

One of the direct signatures which can be connected with a CME onset are flare-associated X-ray ejections of hot plasma. Their characteristics are known mainly from the images made by the Soft X-ray Telescope (SXT) onboard Yohkoh. However, the broad-band SXT filters are not very sensitive to the hot plasma. In this paper several behind-the-limb flares have been chosen. These flares came into view from behind the solar limb but their occurrence was preceded by an X-ray ejection which expanded faster. In consequence, for several minutes the X-ray ejection was seen alone, without the presence of the brighter flare. In such a configuration the spectra recorded by the whole-Sun Yohkoh Bragg Crystal Spectrometer (BCS), which are more sensitive to the hot plasma than the SXT, describe purely the X--ray ejection. Parameters of plasma obtained from a fitting of synthetic spectra to observed spectra are presented and compared to the results from other Yohkoh instruments. Models describing the development of X-ray ejections are discussed and veryfied.