A statistical study on the geoeffectiveness of Earth-directed coronal mass ejections from March 1997 to December 2000

[1] We have identified 132 Earth-directed coronal mass ejections (CMEs) based on the observations of the Large Angle Spectroscopic Coronagraph (LASCO) and Extreme Ultraviolet Imaging Telescope (EIT) on board of Solar and Heliospheric Observatory (SOHO) from March 1997 to December 2000 and carried out a statistical study on their geoeffectiveness. The following results are obtained: (1) Only 45% of the total 132 Earth-directed halo CMEs caused geomagnetic storms with Kp greater than or equal to 5; (2) The initial sites of these geoeffective halo CMEs are rather symmetrically distributed in the heliographic latitude of the visible solar disc, while asymmetrical in longitude with the majority located in the west side of the central meridian; (3) The frontside halo CMEs accompanied with solar flares (identified from GOES-8 satellite observations) seem to be more geoeffective; (4) Only a weak correlation between the CME projected speed and the transit time is revealed. However, for the severe geomagnetic storms (with Kp greater than or equal to 7), a significant correlation at the confidence level of 99% is found.