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 analyzed moving CMEs with oscillation-averaged velocities varying within a wide range. Investigations in the past several years have identified the CME boundary positions relying on data in various CME catalogs providing the positions of the most remote and generally fastest part of the CME boundary. Unlike the previous investigations, we examined the velocity oscillations of both the CME (i.e., its body) and the CME-related shock for relatively fast CMEs. The characteristics of the two structures have been found to differ noticeably. In all cases considered, it was found that the amplitude of velocity oscillations was higher for a shock than for a CME body. In 7 out of 16 cases, the period of shock velocity oscillations is longer than the period of CME velocity oscillations; in 6 cases it is shorter.