Journal article
Waves generated by pulsed electron beams
STAR Laboratory, Department of Electrical Engineering, Stanford University, Stanford, CA 94305-4055, U.S.A.1
Department of Physics and Astronomy, University of Iowa, Iowa City, IA 52242, U.S.A.2
During the Spacelab-2 flight of July, 1985, electron beams (1 keV, 100 mA) square-wave modulated at ELF and VLF were emitted from the space shuttle. The wave fields generated by the beam were monitored by a free-flying sub-satellite at distances up to 300 m perpendicular to the beam. The amplitude of the magnetic and electric fields were modulated by the spin of the satellite.
This modulation allows the study of the wave polarization. Results for a 7 min duration beam sequence in which the beam was pulsed at 1.22 kHz are presented and compared with recent predictions for wave-fields stimulated by ideal helical electron beams propagating in a magnetized plasma. It is found that the predicted magnetic field amplitude of the first harmonic of the beam pulsing frequency (below the lower hybrid frequency) is in agreement with observations, however, the predicted and the observed polarizations are entirely different.
For the higher harmonic components (above the lower hybrid frequency), theory predicts order of magnitude larger magnetic field amplitudes than observed. It is concluded that the theory does not adequately model the full distribution of the radiating current.
Language: | English |
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Year: | 1990 |
Pages: | 137-142 |
ISSN: | 18791948 and 02731177 |
Types: | Journal article |
DOI: | 10.1016/0273-1177(90)90287-A |