A Pi 2 pulsation event was observed at the dip- equator (Huancayo, Peru; 75 ¿W, 0306 LT) during the period from 0806 to 0815 UT on March 25, 1986. Geosynchronous satellite data from GOES 6 (0106-0115 LT) and 1984-129 (2146--2155 LT) in the midnight sector during the above interval were examined to investigate the field and particle (electron, 30--300 keV; proton, 72--573 keV) signatures in space that correlated with the Pi 2 pulsation at the dip- equator. The Pi 2 onset was seen to occur in association with the flux enhancement both for electrons and ions, and concurrent modulation of the flux and magnetic fields lasted thereafter for 10 min. In spite of a local time separation of 5.3 hours between the ground and satellite locations, the waveform in space resembled that of the Pi 2 on the ground. To account for such coherent oscillations between space and ground locations, we invoke a transient response of the nightside magnetosphere to the injected particles at the substorm expansion onset, rather than hydromagnetic instabilities arising from the interactions with the injected hot particles.¿ 1997 American Geophysical Union