The Geos 2 electron gun experiment has been used to obtain electric field data during the compressional Pc5 pulsation event of Day 300, 1979. The phase relationships between the electric field and magnetic field observations show that the oscillation in the meridian plane appears to be a transverse Alfv¿n standing wave in the second harmonic, while the compressional oscillation is symmetrical about the equatorial plane. Computations of the fields of a guided poloidal wave fit the transverse oscillation well. The oscillation is not completely explained by existing theories. A comprehensive model of the oscillation is presented.