An X1.7 flare at 10:15 UT and a halo CME with a projected speed of 942 km/s erupted from NOAA solar active region 9393 located at N20W19 , were observed on 2001 March 29 .
When the CME reached the Earth , it triggered a super geomagnetic storm ( hereafter super storm ) .
We find that the CME always moved towards the Earth according to the intensity-time profiles of protons with different energies .
The solar wind parameters responsible for the main phase of the super storm occurred on March 31 , 2001 is analyzed taking into account the delayed geomagnetic effect of solar wind at the L1 point and using the SYM-H index .
According to the variation properties of SYM-H index during the main phase of the super storm , the main phase of the super storm is divided into two parts .
A comparative study of solar wind parameters responsible for the two parts shows the evidence that the solar wind density plays a significant role in transferring solar wind energy into the magnetosphere , besides the southward magnetic field and solar wind speed .