Pc 3 pulsations observed near the south polar cusp

Abstract

We have compared high time resolution search coil magnetometer data near local magnetic noon from South Pole Station, Antarctica, for January and June 1983 with energetic particle data from DMSP and DE 2 satellites and with interplanetary magnetic field data from the IMP 8 satellite. Broadband irregular magnetic pulsations with period range 0.5–40 s (Pi 1) observed at South Pole Station are found to be associated with the proximity of strong >10‐keV electron precipitation, with a somewhat weaker dependence on Kp and the proximity of the cusp. Large‐amplitude Pc 3 pulsations (up to 20 nT peak to peak) also appear frequently in the data and are distinguished by their packetlike structure and their nearly monochromatic character. Pc 3 pulsations show little or no correlation with latitudinal position of the cusp, with magnetic activity, or with the presence of >10‐keV electron precipitation, but their occurrence is strongly correlated with the X component of the interplanetary magnetic field, and their frequency is dependent on the magnitude of this field. Our results suggest that no local sources need be postulated to explain the occurrence of Pc 3 pulsations at cusp latitudes and may suggest that upstream wave energy in the Pc 3 frequency range can reach low altitudes on cusp field lines.