On the CME velocity distribution

Abstract

Context. Coronal mass ejections (CMEs) are often categorized into flare-associated and filament-associated types, which logically is incomplete since there are many CMEs of the intermediate type. Aims. With this new classification, this paper aims to reexamine whether flare-associated CMEs and filament eruption-associated CMEs have distinct velocity distributions and to investigate which factors may affect the CME velocities. Methods. We divide the CME events observed from 2001-2003 into three types, i.e., the flare-associated type, the filament eruption-associated type, and the intermediate type. The magnetic environments of the source regions, e.g., the polarity orientation, the chirality of the filaments, etc., are examined. Results. Our results indicate that the P-value of the likelihood between the flare-associated and the filament eruption-associated CMEs is as high as 0.79, which strongly suggests that they are a continuum of events rather than two distinct types. For the filament eruption-associated CMEs, the speeds are found to be strongly correlated with the average magnetic field in the filament channel. It is also found that there is a slight tendency for the filaments with the minority chirality to have weaker magnetic fields, and hence the corresponding CMEs have smaller eruption speeds. A slight tendency is also found for the CMEs associated with non-active region filaments to have higher eruption speeds than those with active region filaments. However, the polarity orientation of the filament channel has little effect on the eruption speed. © ESO 2006.