Interplanetary Propagation Of Coronal Mass Ejections: Results From Interplanetary Scintillation Observations Using EISCAT

Coronal mass ejections (CMEs) and their interplanetary counterparts have been familiar from white-light images of the corona and in-situ measurements in interplanetary space for more than 30 years, but there are still significant gaps in our understanding of the evolution of these events with distance from the Sun and their interaction with the background solar wind. Measurements of interplanetary scintillation (IPS) have been used to study transient events in the solar wind for many years. Characteristic signatures of the passage of interplanetary CMEs (iCMEs) across the IPS ray-path were recognised by Klinglesmith (1997) and this work was subsequently developed using data from the EISCAT facility by Canals (2002). In this study we use the set of criteria for passage of an iCME developed by Canals to determine which IPS observations show the interplanetary counterparts of CMEs observed by LASCO and present a series of case studies of iCMEs, comparing velocities of transients observed in the corona, in interplanetary space and by spacecraft at 1 AU and beyond with the speed of the background solar wind ahead of each event. These results support previous radio-burst studies of interplanetary shocks in that they show that slow events are accelerated and fast ones slowed as they move out into interplanetary space and extend them by confirming that iCME speeds converge on the speed of the background solar wind as distance from the Sun increases.