Plasma Waves Stimulated by Electron Beams in the Lab and in the Auroral Ionosphere

Abstract

Energetic electron beams are frequently used as active probes of space plasmas. Often the assumed test particle nature of these electrons is violated when the electron beam stimulates plasma wave emissions. Such complex phenomena have been observed on rockets and satellites and are being modeled in laboratory plasmas. The large vacuum chamber at NASA Johnson Space Center in Houston, Texas has been used for modeling F-region type ionospheric plasmas. A VLF receiver has been flown into an auroral plasma and the spectra from this flight will be compared to VLF spectra obtained in the NASA/JSC laboratory chamber. The electron beam is believed to have produced beam plasma discharge (BPD) on the rocket similar to that seen in the lab. At times during the rocket flight the electron beam was operated at 4 kilovolts and the electron current modulated at 3 kilohertz from 0 to 80 milli-amps. This resulted in the beam pulsing in and out of BPD and a variety of propagating wave modes.