On the CME velocity distribution

Department of Astronomy, Nanjing University, Nanjing 210093, PR China e-mail: chenanqin@hotmail.com; chenpf@nju.edu.cn

Received: 6 April 2006
Accepted: 9 May 2006

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.