At 0027 UT on July 29, 1977 an interplanetary shock wave arrived at the front side magnetosphere and triggered substantial geomagnetic activity throughout the day. The propagation of the resulting MHD wave within the magnetosphere has been studied with measurements from a total of six satellites in (or near) the geostationary orbit and the interplanetary space and groundbased magnetometers. At the time of the SSC the European GEOS 1 was located at R=6.7 RE and 1300 LT providing accurate reference measurements for the hydromagnetic impulse spreading out in the magnetosphere. The signal transmission from the front side magnetopause down to the equatorial ionosphere correspond to an average wave speed of v=600 km/s. A propagation speed of v=910 km/s was found for the signal transmission in the outer magnetosphere in and beyond the geostationary altitude. The results compared reasonably well with model calculations.