QUASI-TRAPPED VLF PROPAGATION IN THE OUTER MAGNETOSPHERE.
AVCO EVERETT RESEARCH LAB EVERETT MASS
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Very low frequency radiation has now been detected in various regions of the magnetosphere, and it seems feasible in the near future to undertake experiments correlating the intensity of such radiation at different points along the ray path. The further suggestion that trapped electrons may generate whistler mode waves in equatorial high L regions, has stimulated interest in the propagation of such waves in an unducted magnetosphere. A simplified but not unreasonable density distribution, proportional to magnetic field strength along the equator and constant along field lines, has been used. For frequencies well below the electron cyclotron frequency and propagation vectors not too close to perpendicular to the magnetic field, this leads to an index of refraction relation independent of wave frequency and L. Waves originating at the equator rapidly become almost perpendicular to the field. Rough consideration of propagation in the neighborhood of the lower hybrid resonance suggests that low frequency waves will be reflected before reaching the ionosphere and thus be quasi-trapped in the magnetosphere. Such waves would not be observed by low altitude satellites. Waves of sufficiently high frequency should be detectable at low altitudes but would then have wave vectors predominantly perpendicular to the ambient magnetic field and thus considerable energy in the oscillating electric field. Author
- Atmospheric Physics
- Radiofrequency Wave Propagation