A two-type classification of LASCO coronal mass ejection

The causes and origins of Coronal Mass Ejections (CMEs) remain among the outstanding questions in Space Physics. The observations of CMEs by the LASCO coronagraphs on SOHO suggest that there are two distinct types of CMEs. The two types of events can be most easily distinguished by examining height-time plots. The Type A (Acceleration) events produce curved plots that often indicate a constant acceleration. These events are usually associated with pre-existing helmet-streamers, and are often associated with prominence eruptions or filament disappearance. The Type C (Constant speed) events show a constant speed. These events are usually brighter, larger, and faster than Type A events and may be associated with X-ray flares. While the two types of events can be distinguished in other ways, the height-time plots are a simple and unambiguous way to make this identification.