Abstract
From an extensive study of coronal mass ejections (CM Es) observed by the Solwind coronagraph on board of P78-1 satellite from 1979 to 1982, combined with the interplanetary observations of Helios 1 spacecraft, a set of 49 CMEs was confidently associated with interplanetary shocks. Here we look for some possible spatial association of these CMEs with coronal holes and/or active regions at the Sun, and consider also their spatial association with the surface explosive events (flares or disappearing filaments) related to them. We found that in most of the cases when a CME was associated with an interplanetary shock, a coronal hole is found between + 300 of longitude from the corresponding limb. We outiine a possible scenario where all the related events could take place as a result of an MHD destabilization of a large region containing different kinds of magnetic structures and discuss the results reanalyzing the association between CMEs and interplanetary shocks. In particular we find that the observations are consistent with the idea that mass ejections come from closed regions, most probably helmet streamers. But we think that they do not necessarily drive the observed interplanetary shocks. We propose that shocks are instead produced by the sudden increase in the flow velocity of the solar wind from the adjacent coronal hole also affected by the global change in the coronal magnetic structure. Observational evidence supporting the association of interplanetary shocks with sudden changes in coronal holes is presented as well.
