X‐ray coronal changes during Halo CMEs

Using the Yohkoh soft X‐ray images, we examine the coronal structures associated with “halo” coronal mass ejections (CMEs). These may correspond to events near solar disk center. Starting with a list of eleven confirmed halo CMEs over the time range from December 1996 through May 1997, we find seven with surface features identifiable in soft X‐rays, with GOES classifications ranging from A1 to M1.3. These have a characteristic pattern of sigmoid → arcade development. In each of these events, the pre‐flare structure disrupted during the flare, leaving the appearance of compact transient coronal holes. The four remaining events had weak or indistinguishable signatures in the X‐ray images. For the events for which we could see well‐defined coronal changes, we confirm our previous result that the estimated mass loss inferred from the soft X‐ray dimming is a small fraction of typical CME masses [ Sterling & Hudson 1997].