Plasma wave observations near the plasmapause with the S³-A satellite

Summary. In this paper we describe the electric field noise phenomena observed by the S³-A spacecraft near the plasmapause during the magnetic storm of December 16–17, 1971. The most striking and unusual feature of these storm time electric field observations is the occurrence of a region of intense low-frequency (20 to 500 Hz) electrostatic noise bursts just outside the plasmapause boundary. These noise bursts occurred concurrent with the rapid decrease in low-energy (20 ≲ E ≲ 50 kev) ring current protons mirroring near the equator during this storm and may be responsible for the loss of these particles. The characteristics of other phenomena, such as whistlers, ELF hiss, and banded chorus, observed near the plasmapause during this period are also discussed.