A disturbed region and shock wave driven by a coronal mass ejection

The existence of a disturbed region in front of a coronal mass ejection (CME) has been proved; and its variation with increasing CME velocity has been investigated. A plasma density discontinuity that can be interpreted as a shock wave is shown to develop in front of the disturbed region at CME velocities that are about or above the local Alfven velocity. Estimations testify that within the experimental error the observed shock-wave width is of order of the mean free path relative to paired proton-proton collisions at distances R 15-20Re from the Sun center; i.e., conceivably the energy dissipation mechanism in the front is collisional at these distances.