Relation between flare-associated X-ray ejections and coronal mass ejections

In an attempt to identify the direct signatures of coronal mass ejections (CMEs) in soft X-ray wavelengths, we have searched for plasma ejections in Yohkoh soft X-ray telescope (SXT) images in a total of 17 limb flares, and compared the results with the Solar and Heliospheric Observatory LASCO data. A general correlation exists between the presence/absence of the X-ray ejection and the CME. Although the height versus time relation often indicates (under the assumption of constant speed) that the CME onset coincides with the X-ray ejection, the latter probably does not represent the CME front, because the CME speed must result from acceleration, which would put the estimated onset at an earlier time. In some cases, the estimated CME onset time comes well before the impulsive phase of the associated flare. Although the role of the flare-associated plasma ejection in a CME is still unclear, we propose that its occurrence depends on the presence of open field lines, which can be due to a preceding CME. Lastly, we present a rare example of SXT observations of what appeared to be the three-part structure of a CME, which was seen a few minutes before a major flare started.