Observation of shock waves associated with coronal mass ejections from SOHO/LASCO

Theoretical models of coronal mass ejections (CME) predict formation of shock waves in front of eruptive magnetic structures, loops and arches. These shock waves have been detected in the solar wind at large distances from the Sun. However, their observation at short distances in the solar corona has been difficult. We have attempted to identify the shocks in the LASCO data by comparing the radial intensity profiles in limb CMEs with a theoretical model (Stepanova and Kosovichev, 1993). We demonstrate that the shocks can be identified at least in some cases of CME of the simple loop-like geometry. The LASCO observations indicate a turbulent structure for the flows associated with the shocks. We have determined the velocity of such shocks and expanding loops and compared with our model. In most cases, the observed expansion speed was rather slow possibly meaning that no significant disturbances on the solar surface were involved in initiating the eruptions.