Coronal mass ejections-Propagation time and associated internal energy

In this paper, we analyze 91 coronal mass ejection (CME) events studied by Manoharan et al. (2004) and Gopalswamy and Xie (2008). These earth-directed CMEs are large (width > 160 degrees) and cover a wide range of speeds (similar to 120-2400 km s(-1)) in the LASCO field of view. This set of events also includes interacting CMEs and some of them take longer time to reach 1 AU than the travel time inferred from their speeds at 1 AU. We study the link between the travel time of the CME to 1 AU (combined with its final speed at the Earth) and the effective acceleration in the Sun-Earth distance. Results indicate that (1) for almost all the events (85 out of 91 events), the speed of the CME at 1 AU is always less than or equal to its initial speed measured at the near-Sun region, (2) the distributions of initial speeds. CME-driven shock and CME speeds at 1 AU clearly show the effects of aero-dynamical drag between the CME and the solar wind and in consequence, the speed of the CME tends to equalize to that of the background solar wind, (3) for a large fraction of CMEs (for similar to 50% of the events), the inferred effective acceleration along the Sun-Earth line dominates the above drag force. The net acceleration suggests an average dissipation of energy similar to 10(31-32) ergs, which is likely provided by the Lorentz force associated with the internal magnetic energy carried by the CME. (C) 2011 Elsevier Ltd. All rights reserved.