The Ice Cream Cone Model for Inversing Geometrical Properties of Halo Coronal Mass Ejections

It is suggested recently that most of halo coronal mass ejections (CMEs) may be formed by an ice cream cone-like shell of dense CME electrons. We improve our cone model (Zhao, Plunkett and Liu, 2002) to include the contribution of the top surface of the ice cream part as well as the cone part to the shape of the halo CMEs. It is found that for an ice cream cone with a half sphere sitting on the base of a cone, the projection of the top surface of the ice cream part on the plane of the sky is a half ellipse with its semi-minor axis aligned with the line connecting the center of the ellipse to the Sun’s disk center and located in the side of the major axis far away from the Sun’s disk center. This front half ellipse is greater than the front half ellipse produced by the cone part when the angle of the central axis of the ice cream cone from the plane of the sky is less than 45 degrees; when the angle is greater than 45 degrees, the whole elliptic halo is symmetric. In both cases, the such geometrical and kinematical properties as the angular width, the direction of the central axis, and the accelaration of the halo CME can be uniquely determined. — The SHINE 2005 Workshop, July 11 – 15, 2005, The Big Island