Timing of the soft X-ray blue-wing and the hard X-ray burst from observations by Yohkoh

Abstract

A knowledge of the relative timing of the hard X-ray burst and emission in soft X-rays is helpful in deciding between a number of theoretical models that describe the mechanism of a solar flare. Here we continue a study of this relationship using observations from the Yohkoh Bragg Crystal Spectrometer and Hard X-ray Telescope, together with supporting observations from the CGRO Batse experiment. The enhanced capabilities of the instruments onboard Yohkoh have made it possible to study the problem in a way that was not previously possible. A study of the timing, intensity and evolution of the soft X-ray blue-wing shows that there is no simple relationship between hard and soft X-ray emissions; strong blue-wings sometimes result from relatively weak hard X-ray bursts; the burst responsible for the blue wing need not be the first or most intense burst associated with the flare; the blue-wing is found to follow very closely after the hard X-ray burst. We also discuss timing issues and why other researchers may have reached different conclusions on this matter.