VLF Emissions in the Magnetosphere

Abstract

Recent observations of both naturally occurring and triggered VLF emissions (a few KHz) made on the ground, aboard rockets, and aboard satellites are discussed. Although reference is made to auroral‐zone emissions, attention is concentrated on midlatitude discrete emissions such as chorus. Following Brice [1964] and Kennel and Petschek [1966], the signals are interpreted as arising from the transverse resonance (or cyclotron) instability of magnetospheric plasma in the equatorial plane in the vicinity of the plasmapause. The energy of the gyroresonant electrons is estimated; the precipitation of these energetic electrons from the radiation belts is a consequence of the interaction.