Wednesday, March 20, 2013

1303.4059 (Chenglong Shen et al.)

Full halo coronal mass ejections: Do we need to correct the projection effect in terms of velocity?    [PDF]

Chenglong Shen, Yuming Wang, Yang Liu, Pinzhong Ye, S. Wang
The projection effect would distort our understanding of coronal mass ejections (CMEs) and influence the space weather forecasting. To evaluate the projection effect, the de-projected kinematic parameters of full halo CMEs (FHCMEs) listed in the CDAW CME catalog from 2007 March 1 to 2012 May 31 are studied by applying the Graduated Cylindrical Shell (GCS) model. It is revealed that, although these CMEs are all full halo in the view angle of SOHO, the de-projected parameters, including the propagation direction and angular width, could vary in a large range. Projection effect is a major but not only reason causing a CME being halo. By comparing the de-projected velocity with projected velocity of these CMEs, we find that not all of FHCMEs need to be corrected for their velocities; only the FHCMEs originating within 45$^\circ$ of the Sun-Earth line and moving slower than 900 km s$^{-1}$ in the plane-of-sky should be corrected.
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