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In this paper, we analyze 91 coronal mass ejection (CME) events studied byManoharan et al. (2004) and Gopalswamy and Xie (2008). These earth-directedCMEs are large (width $>$160$^\circ$) and cover a wide range of speeds($\sim$120--2400 {\kmps}) in the LASCO field of view. This set of events alsoincludes interacting CMEs and some of them take longer time to reach 1 AU thanthe travel time inferred from their speeds at 1 AU. We study the link betweenthe travel time of the CME to 1 AU (combined with its final speed at the Earth)and the effective acceleration in the Sun-Earth distance. Results indicate that(1) for almost all the events (85 out of 91 events), the speed of the CME at 1AU is always less than or equal to its initial speed measured at the near-Sunregion, (2) the distributions of initial speeds, CME-driven shock and CMEspeeds at 1 AU clearly show the effects of aero-dynamical drag between the CMEand the solar wind and in consequence, the speed of the CME tends to equalizeto that of the background solar wind, (3) for a large fraction of CMEs (for$\sim$50% of the events), the inferred effective acceleration along theSun-Earth line dominates the above drag force. The net acceleration suggests anaverage dissipation of energy $\sim$10$^{31-32}$ ergs, which is likely providedby the Lorentz force associated with the internal magnetic energy carried bythe CME.

Coronal Mass Ejections - Propagation Time and Associated Internal Energy