Arrival time of halo coronal mass ejections in the vicinity of the Earth

We describe an empirical model to predict the 1-AU arrival time of halo CMEs. This model is based on the effective acceleration described by Gopalswamy et a]. (2000a, Geophys. Res. Lett., 27, 145). We verify the Helios/Pioneer Venus Orbiter(PVO) estimation of the effective acceleration profile (Gopalswamy et al. 2001a, J. Geophys. Res., 106, 29207) by considering all full halo CMEs recorded by SOHO/LASCO coronagraphs until the end of 2002. In comparison with previous studies, the present work includes CMEs of a wider range of initial velocities. To improve the accuracy of prediction, we propose to introduce the effective acceleration from two groups of CMEs only, which are expected to have no acceleration cessation at any place between the Sun and Earth. In addition, we consider acceleration cessation distance dependent on initial velocities of a given event CME. For a detailed analysis of this model, we examine projected sky-plane and space speeds (Michalek et al. 2003, ApJ, 584, 472) of CMEs. We show that a correct acceleration profile is crucial for the estimation of 1 AU arrival time of halo CMEs. We estimate that the CME arrival times can be predicted with an average error of 9 and 11 for space and sky-plane initial velocities, respectively.