Oblique Ionospheric Heating and Effects on Radio Propagation.

摘要

The process of self focusing of high intensity Gaussian HF electromagnetic beams in the ionosphere is studied. Analytic expressions for threshold intensity, growth rate and focal length are obtained in terms of the beam parameters for self focusing due to the ponderomotive force. Spectral broadening of VLF waves traversing the ionosphere has been studied. Two mechanisms, nonlinear scattering and parametric excitation of lower hybrid waves are shown to provide nonlinear mode conversion of VLF waves into electrostatic plasma modes in the presence of ionospheric density striations. The proposed mechanisms can be tested in an experiment that combines the operation of HF and VLF ionospheric heaters. Keywords: Oblique ionospheric modification. (edc)