X-ray ejecta, white-light CMEs and a coronal shock wave

We report on a coronal shock wave inferred from the metric type II burst of 13 January 1996. To identify the shock driver, we examined mass motions in the form of X-ray ejecta and white-light coronal mass ejections (CMEs). No ne of the ejections could be considered fast (> 400 km s(-1)) events. In wh ite light, two CMEs occurred in quick succession, with the first one associ ated with X-ray ejecta near the solar surface. The second CME started at an unusually large height in the corona and carried a dark void in it. The fi rst CME decelerated and stalled while the second one accelerated, both in t he coronagraph field of view. We identify the X-ray ejecta to be the driver of the coronal shock inferred from metric type II burst. The shock speed r eported in the Solar Geophysical Data (1000-2000 km s(-1)) seems to be extr emely large compared to the speeds inferred from X-ray and white-light obse rvations. We suggest that the MHD fast-mode speed in the inner corona could be low enough that the X-ray ejecta is supermagnetosonic and hence can dri ve a shock to produce the type II burst.