Velocity oscillations in CME and related shock: a comparative analysis

A number of studies have concluded that the velocity of coronal mass ejections (CME) does not change monotonically with time, but exhibits oscillations. They analysed moving CMEs with oscillation-averaged velocities varying within a wide range. Investigations in the past several years identified the CME boundary positions relying on data in various CME catalogues providing the positions of the most remote and, generally, fastest part of the CME boundary. No attention was paid, however, to the fact that, for fast enough CMEs, the outer part of the structure observed in the coronagraph field of view and defined as a `CME' in the catalogues, is indeed the CME-related shock. Unlike the previous investigations into the velocity oscillations of a CME moving in a coronagraph field of view, we examined the velocity oscillations of a CME (i.e. its body) separately from the velocity of the CME-related shock, for relatively fast CMEs. The characteristics of the two structures have been found to differ noticeably.