Coronal mass ejections (CMEs) involve the expulsion of significant amo
unts of mass and magnetic flux into the heliosphere, a process which i
mplies an unobserved continuous buildup of the net interplanetary magn
etic flux. Some form of disconnection of the flux near the Sun, either
directly associated with the CME or occurring elsewhere in the corona
, appears to be required to prevent this buildup. Field line reconnect
ion in the wake of CMEs is also a fundamental aspect of some types of
magnetically driven eruptive flare/CME models. However, to date there
have been very few reports of CMEs which exhibited evidence for discon
nection, despite the detection of several thousand CMEs over nearly 2
decades of observations. We report on the results of a systematic sear
ch for candidate magnetic disconnection features, defined as transient
large-scale, concave-outward bright regions usually following the CME
leading edge, using both ground-based solar eclipse and spaceborne co
ronagraph data. We conclude that greater than or equal to 10% of all C
MEs observed in the corona have possible disconnection structures. We
propose a simple classification scheme for these features based on the
ir morphology. The most common type of candidate disconnection feature
(65% of all the features) had a circular or ovoid shape; 35% of the f
eatures consisted of concave-outward partial arcs. The average leading
edge speed and latitudinal span of these CMEs were slightly less than
those of typical CMEs. The results are discussed in the context of re
cent studies of magnetic disconnection and reconnection in the corona.