Accession Number : ADP006504

Title :   Ionospheric Heating With Oblique HF Waves,

Corporate Author : PACIFIC-SIERRA RESEARCH CORP LOS ANGELES CA

Personal Author(s) : Field, Edward C., Jr. ; Bloom, Ron M.

Report Date : OCT 1990

Pagination or Media Count : 13

Abstract : This paper presents calculations of ionospheric electron density perturbations and ground-level signal changes produced by intense oblique high-frequency (HF) transmitters. Our analysis takes into account radio field focusing at caustics, the consequent joule-heating of the surrounding plasma, heat conduction, diffusion, and recombination processes--these being the effects of a powerful oblique modifying, wave. It neglects whatever plasma instabilities might occur. We then seek effects on a secondary 'test wave that is propagated along the same path as the first. Our calculations predict ground-level field-strength reductions of several dB in the test wave for modifying waves having ERP in the 85-to-90 dBW range. These field-strength changes are similar in sign, magnitude, and location to ones measured in Soviet experiments. Our results are sensitive to the the model ionosphere assumed, so future experiments should employ the widest possible range of frequencies and propagation conditions. An effective power of 90 dBW seems to be a sort of threshold that, if exceeded, results in substantial rather than small signal changes. Our conclusions are based solely on joule-heating and subsequent defocusing of waves passing through caustic regions.

Descriptors :   *IONOSPHERIC DISTURBANCES, *RADIO WAVES, CAUSTICS, DENSITY, DIFFUSION, ELECTRON DENSITY, FOCUSING, GROUND LEVEL, HEAT, HEATING, MODELS, PATHS, PERTURBATIONS, POWER, RADIO FIELDS, REDUCTION, REGIONS, SECONDARY WAVES, TEST AND EVALUATION, RADIO TRANSMITTERS, IONOSPHERIC PROPAGATION, RADIO SIGNALS, HIGH FREQUENCY.

Subject Categories : Atmospheric Physics

Distribution Statement : APPROVED FOR PUBLIC RELEASE