Abstract: The correlation analyses between the solar wind parameters (V,T,N and Bz) and the geomagnetic activity for the different periods of solar activity of 20th solar cycle are carried out.Further more,the solar wind parameters and its daily RMS of hourly mean values are compared to geomagnetic activity via regression analyses for the solar maximum and minimum years of the same cycle.The results show that in addition to the magnetic storms due to the reconnection between the IMF and the earth's magnetic field,which is accepted generally,there is another geomagnetic disturbance which is independent of Bz and is caused by solar wind with high temperature,high speed and thermo-nonumiform.