Stimulated Emission of Energetic Particles (SEEP).

Abstract : An active satellite-ground coordinated space plasma experiment was conducted in which electrons were precipitated from the radiation belts into the ionosphere by the controlled injection of VLF signals from ground-based transmitters. In this experiment Stimulated Emission of Energetic Particles (SEEP), four operational VLF transmitters were operated in special controlled formats at times of overpasses of the low-altitude polar- orbiting satellite S81-1. The results confirm the hypothesis that electrons can be precipitated from the radiation belts by ground-based VLF transmitters, and they provide information relating to the effects of such precipitation on the ionosphere. In addition, the precipitation of electrons by VLF waves associated with lightning was measured for the first time from a satellite. Many other important findings were made with the SEEP data. These include the following: 1) An assessment was made of the relative contributions of hiss, lightning and VLF transmitter waves to electron precipitation from the slot region, 2) discovery of the frequent occurrence of multiple peaks in the energy spectra of electrons trapped at low altitudes, 3) observation of electron pulsations near the trapping boundary and 4) discovery of bremsstrahlung x-ray images of small isolated patches of energetic electron precipitation at high latitude.