Accession Number : ADP006497

Title :   Theory of a Thermal Resonance Instability in the E-Region of the Ionosphere,

Corporate Author : DANISH METEOROLOGICAL INST COPENHAGEN

Personal Author(s) : Hoeeg, P.

Report Date : OCT 1990

Pagination or Media Count : 15

Abstract : Auroral region modulation components have shown, that strong electromagnetic HF waves are generating short-scale field-aligned irregularities in the E region of the high latitude ionosphere. For overdense conditions the instabilities are excited close to the reflection altitude of the 0-mode heating wave. The theory presented here for a thermal resonance instability are capable of explaining these observations for magnetically quiet to moderate disturbed conditions. We consider the dispersion relation for a thermal resonance instability, where differential heating by collisional dissipation is more important than the action of the ponderomotive force. Thus special attention is paid to the transport theory, when a constant ambient electric field is applied to the plasma. For irregularities with transverse scale lengths much smaller than the wavelength of the heating wave, thermal nonlinearity causes strongly enhanced electron density fluctuations in regions of excess heating wave intensity. In the region, where the upper hybrid frequency of the plasma matches the heating wave frequency, the initial growth of irregularities takes place.

Descriptors :   *IONOSPHERIC DISTURBANCES, ALTITUDE, CONSTANTS, DISPERSION RELATIONS, DISPERSIONS, DISSIPATION, E REGION, ELECTRIC FIELDS, ELECTRON DENSITY, ELECTROSTATICS, HEATING, HIGH LATITUDES, INSTABILITY, INTEGRAL EQUATIONS, INTENSITY, IONOSPHERE, LATITUDE, MODULATION, QUIET, REGIONS, RESONANCE, RESPONSE, SCALE, THEORY, TRANSVERSE, AURORAE, TRANSPORT PROPERTIES.

Subject Categories : Atmospheric Physics

Distribution Statement : APPROVED FOR PUBLIC RELEASE