The magnetic field experiment on the Viking satellite detected long-period compressional oscillations with amplitudes ranging from 2 to 5 nT and periods ranging from 7 to 23 min on nine Viking orbits covering a wide range of polar and subauroral latitudes during the period from March to August 1986. We present a case study of an event on June 18, 1996, in which similar long-period pulsations were also observed by a global network of more than 50 ground magnetometers and by the GOES-5 and GOES-6 spacecraft. The magnetic field variations throughout the auroral, midlatitude, and equatorial regions, at Viking, GOES-5, and GOES-6 were approximately in phase, whereas the variations at some morningside stations were a half-wave period out of phase. We interpret these long-period oscillations as evidence for periodic compressions and inflations of the magnetosphere driven by solar wind pressure pulses. The relative time delays of the peak variations observed by GOES-5, GOES-6, Viking, and the ground-based stations are consistent with an event originating on the prenoon magnetopause whose signatures spread both poleward and antisunward on both sides of local noon. ¿ 2000 American Geophysical Union