Coronal dimmings and energetic CMEs in April‐May 1998

Abstract

We have analyzed the coronal dimmings for seven fast (> 600 km/s) coronal mass ejections (CMEs) occurring between 23 April and 9 May which were associated with flares from NOAA active region (AR) 8210. Each of these CMEs had at least one group of interplanetary radio bursts associated with them. These dimming regions were identified by their strong depletion in coronal EUV emission within a half hour of the estimated time of CME lift‐off. They included areas which were as dark as quiescent coronal holes as well as other regions with weaker brightness depletions. While the location of the active region and the associated flare did not correspond well with the coronagraph observations, we found that the extended dimming areas in these events generally mapped out the apparent “footprint” of the CME as observed by white‐light coronagraph. We briefly discuss the implications of these results on models of CME topology.