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X-ray Coronal Mass Ejection?
The two panels at the top show the ejection of coronal mass from a long-duration solar flare observed by Yohkoh/SXT on 21 February 1992. The flare was on the east limb, shown by the curved lines; S is up in this display. The panels at the bottom are copies with lines pointing out the remarkable phenomena: first, the upper corona dims strikingly in the fifteen minutes between the images. The dimming is most pronounced above the long dashed line. The dimming is the result of violent outward motion apparent in a movie representation of these images: a coronal mass ejection "caught in the act" at X-ray temperatures. Second, a compact oval feature (arrow) emerges, apparently from the cusp of the flare below, and half-disappears from the top of the field of view in the later image. The upward motion accelerates from 100 km/sec to about 150 km/sec as the feature traverses the image. This ejection leaves a nearly vertical linear feature trailing behind as it, suggestive of the current sheet required by magnetic reconnection theory. The onset of mass ejection coincided, as precisely as we can tell, with the onset of soft X-ray emission, and (another discovery) with the onset of nonthermal hard X-rays as detected by the BATSE instrument on Compton/GRO.
H. Hudson, J. Lemen, submitted 2-May-1995