Propagation of normal and faster CMEs in the interplanetary medium

Abstract

We have analyzed 101 Coronal Mass Ejection (CME) events and their associated interplanetary CMEs (ICMEs) and interplanetary (IP) shocks observed during the period 1997–2005 from the list given by Mujiber Rahman et al. (2012). The aim of the present work is to correlate the interplanetary parameters such as, the speeds of IP shocks and ICMEs, CME transit time and their relation with CME parameters near the Sun. Mainly, a group of 10 faster CME events (VINT>2200km/s) are compared with a list of 91 normal events of Manoharan et al. (2004). From the distribution diagrams of CME, ICME and IP shock speeds, we note that a large number of events tends to narrow towards the ambient (i.e., background) solar wind speed (∼500km/s) in agreement with the literature. Also, we found that the IP shock speed and the average ICME speed measured at 1AU are well correlated. In addition, the IP shock speed is found to be slightly higher than the ICME speed. While the normal events show CME travel time in the range of ∼40–80h with a mean value of 65h, the faster events have lower transit time with a mean value of 40h. The effect of solar wind drag is studied using the correlation of CME acceleration with interplanetary (IP) acceleration and with other parameters of ICMEs. While the mean acceleration values of normal and faster CMEs in the LASCO FOV are 1m/s2, 18m/s2, they are −1.5m/s2 and −14m/s2 in the interplanetary medium, respectively. The relation between CME speed and IP acceleration for normal and faster events are found to agree with that of Lindsay et al. (1999) and Gopalswamy et al. (2001) except slight deviations for the faster events. It is also seen that the faster events with less travel time face higher negative acceleration (>−10m/s2) in the interplanetary medium up to 1AU.