Determining the state of the corona prior to coronal mass ejections (CMEs) is crucial to understanding and ultimately predicting solar eruptions. A common and compelling feature of CMEs is their three-part morphology as seen in white light observations of a bright expanding loop, followed by a relatively dark cavity, and lastly a bright core associated with an erupting prominence/filament.

Here is a catalogue providing detailed analysis of 98 white light cavities observed by MLSO's Mk4 coronameter:

Catalogue of MLSO/Mk4 White Light Cavities (1998-2004)