Magnetospheric magnetic field variations as a response to sudden changes of the solar wind dynamic pressure

We compare the sharp magnetic field pulses measured by geosynchronous satellites GOES-8, 9, and 10 with the large and fast changes of the solar wind dynamic pressure observed onboard the Interball-1 satellite. More than 200 solar wind pressure changes, measured with high time resolution (1 sec.) during the 1996-1999, were selected for this study. We found that about 70% of the pressure changes produced similar changes of geosynchronous magnetic field magnitude. The signs of the pressure and magnetic field changes are the same in all cases independent of the GOES satellite position in local time. But the amplitude of the geomagnetic field response strongly depends on the location of the GOES satellite relative to the noon meridian; the maximum amplitude is observed near noon. The time delay between the pressure and magnetic field pulses was investigated and this delay is significantly affected by the inclination of the pressure front to the Sun-Earth line.