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:

HAO / MLSO is now providing daily composite images of the solar corona as seen from 3 viewing angles: STEREO B, Earth-Sun, and STEREO-A. The STEREO A/B composites consist of SECCHI images from: EUVI (inner corona seen against the solar disk), the MLSO MK4 K-Coronameter (blue), the COR1 Coronagraph (green) and the COR2 Coronagraph (in red). The SOHO/MK4 composite combines EIT (solar disk), MK4 (blue) and LASCO C2 (red). MK4 images are NOT rotated to match the STEREO viewing angles.