The experimental saturation spectrum of parametric instabilities
Abstract
Intense high frequency electromagnetic radiation was used to excite parametric instabilities in the stable F region ionospheric plasma. The saturation spectrum of the resulting enhanced electron plasma oscillations was measured using a 430-MHz incoherent backscatter radar. Particular attention was given to the geometrical details of the wave plasma coupling interactions. The shape of the saturation spectrum was shown to strongly depend on the strength of the induced plasma line enhancement. For small enhancements, the spectrum is a diffusive cascade of energy to lower frequencies. In this case, the parametric excitation was found to be below threshold and the enhanced plasma oscillations were stabilized through a nonresonant mode coupling. For greater plasma line enhancements, distinct spectral features appear in association with the formation of satellite plasma waves. These results are in agreement with the theory that nonlinear Landau damping by ions becomes the dominant saturation mechanism above instability threshold.
- Publication:
-
Ph.D. Thesis
- Pub Date:
- November 1977
- Bibcode:
- 1977PhDT........46D
- Keywords:
-
- Absorption Spectra;
- Electromagnetic Radiation;
- F Region;
- Ionospheric F-Scatter Propagation;
- Electron Plasma;
- Landau Damping;
- Plasma Oscillations;
- Scatter Propagation;
- Communications and Radar