CME Initiation and Evolution in the Corona

Evidence for the existence of a flux rope in the source volume of coronal mass ejections (CMEs) has been accumulating in recent years, supporting models of CME initiation that involve the loss of a flux rope equilibrium. Such models allow detailed, comparative studies of the various interactions of the CME flux rope with the coronal field, which will be reviewed. It has been demonstrated that the height profile of the overlying field strongly influences the CME speed. Important processes governing the magnetic orientation are the rotation of the CME flux rope by the coronal shear field component, the writhing of the rope by the helical kink mode, reconnection with complex ambient field, and eventually the alignment with the heliospheric current sheet. Interactions with coronal holes or nearby flux concentrations, the guidance by a helmet streamer, reconnection with the ambient field, and the curvature of the filament channel can cause considerable deviations of the CME path from the radial direction.