VLF wave injection into the magnetosphere from Siple Station, Antarctica

Radio signals in the 1.5- to 16-kHz range transmitted from Siple Station, Antarctica (L=4), are used to control wave-particle interactions in the magnetosphere. Observations at the conjugate point show signal growth and triggered emissions including risers, fallers, and hooks. Growth rates of the order of 100 dB/s and total gains up to 30 dB are observed. Triggered emissions may be cut off or have their frequency rate of change altered by Siple pulses. Similar effects occur in association with harmonics from the Canadian power system. The observed temporal growth is predicted by a recently proposed feedback model of cyclotron interaction. Plasma instability theories predicting only spatial growth are not in accord with these observations. Possible applications include study of nonlinear plasma instability phenomena, diagnostic measurements of energetic particles trapped in the magnetosphere, modification of the ionosphere through control of precipitation, and VLF communication through the magnetosphere.