The Speed Distributions of CMEs after the Projection Correction

Abstract

Observations of coronal mass ejections (CMEs) with coronagraphs are subject to the projection effect, which results in statistical errors in many properties of CMEs, such as the speed. In this paper, using the method based on the cone model to correct the speeds of CMEs due to the projection effect, we study the speed distribution of CMEs before and after correction for 1691 CMEs only associated with flares (type-FL CMEs) and 610 CMEs only associated with filament eruptions (type-FE CMEs) observed by the Large Angle and Spectrometric Coronagraph Experiment on board the Solar and Heliospheric Observatory (SOHO/LASCO) from September 1996 to September 2007, corresponding to almost an entire solar cycle. The results are concluded as follows: (1) before and after the correction, type-FL and type-FE CMEs have quite similar distribution of speed with almost the same average speed; (2) before and after the correction, type-FL and type-FE CMEs have quite similar distribution of the natural logarithm of speed. Our results do not favor that CMEs should be classified into two distinct types, i.e. slow CMEs that are associated with filament eruptions and fast CMEs associated with solar flares.