Pc 4 and Pc 5 pulsations during storm recovery

A strong pulsation event was observed in the magnetosphere near L = 5 with the flux gate magnetometer on Explorer 45. The event occurred near 2300 UT on June 18, 1972, during the recovery phase of a large magnetic storm. Explorer 45 was in the afternoon quadrant, and the event was also observed at many day side, ground level observatories at high and low latitudes. The event had a complex spectrum with distinct pulsations near 2, 6, and 14 mHz (500-, 160-, and 70-s periods). The two lower-frequency pulsations were also observed on the ground. A comparison of the frequencies and polarizations of satellite and ground observations indicates that the event was similar to events observed recently along a latitudinal chain of ground stations in Canada.