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Ong, R. S. B.

Publications and source records attributed to Ong, R. S. B..

13 records
All sourcesNASA NTRSDOE OSTI
NASA NTRS1984

Effects of energetic heavy ions on electromagnetic ion cyclotron wave generation in the plasmapause region

An expression for electromagnetic ion cyclotron convective growth rates is derived. The derivation of the dispersion relation and convective growth rates in the presence of a multicomponent energetic and cold plasma is presented. The effects that multiple heavy ions in the ring current and cold plasma produce in the growth and propagation characteristics of ion cyclotron waves are explored. Results of growth rate calculations using parameters consistent with conditions in the plasmapause region during the early recovery phase of geomagnetic storms are presented and compared with ground-based and satellite observations of waves in this region. The geophysical implications of the results are discussed.

Kozyra, J. U.↗
NASA NTRS1983

Excitation of an electrostatic wave by a cold electron current sheet of finite thickness

Calculations for the threshold of current-driven instabilities and the growth rates of ion acoustic and electrostatic ion cyclotron instabilities in a magnetized plasma driven a current sheet with a finite width are presented. Maxwellian equations are employed to model the velocity distributions of electrons and ions in a direction perpendicular to the sheet. A dispersion relation is defined for the regions of instability, and boundary conditions are characterized in order to obtain a set of eigenvalue equations. Thresholds are delineated for various regions, including ducted mode solutions where only ion-acoustic waves are excited in areas where the frequency range significantly exceeds the ion cyclotron frequency. When a constant electron drift velocity is present, a thick current sheet is more unstable than a thin one. Fewer modes become unstable with a thinner sheet.

Hwang, K. S.↗
NASA NTRS1981

Statistical study of precipitating electrons

Energy spectra of precipitating electrons are fitted to the sum of three distributions: a power law, a Maxwellian and a Gaussian. This fitting procedure determines seven parameters which characterize the essential features of each spectrum. These characteristic parameters are used to carry out various studies involving precipitating electrons. It is shown that the absence of the power-law population from a particular spectrum is related to the softness of the precipitating primary flux, that the Maxwellian temperature and the Gaussian peak energy have a positive correlation the strength of which varies with local time, that the upward moving Gaussian population has a loss cone distribution, and that the one dimensional velocity distribution parallel to the magnetic field occasionally displays a plateau or a hump on the tail.

Fontheim, E. G.↗
NASA NTRS1979

Turbulent transport and heating in the auroral plasma of the topside ionosphere

Using plasma parameters from a typical stormtime ionospheric energy balance model, we have investigated the effects of plasma turbulence on the auroral magnetoplasma. The turbulence is assumed to be comprised of electrostatic ion cyclotron waves. These waves have been driven to a nonthermal level by a geomagnetic field-aligned, current-driven instability. The evolution of this instability is shown to proceed in two stages and indicates an anomalous increase in field-aligned electrical resistivity and cross-field ion thermal conductivity as well as a decrease in electron thermal conductivity along the geomagnetic field. In addition, this turbulence heats ions perpendicular to the geomagnetic field and hence leads to a significant ion temperature anisotropy.

Ionson, J. A.↗
NASA NTRS1978

Effect of anomalous transport coefficients on the thermal structure of the storm time auroral ionosphere

By analyzing an observed storm time auroral electron temperature profile it is shown that anomalous transport effects strongly influence the thermal structure of the disturbed auroral ionosphere. Such anomalous transport effects are a consequence of plasma turbulence, the existence of which has been established by a large number of observations in the auroral ionosphere. The electron and composite ion energy equations are solved with anomalous electron thermal conductivity and parallel electrical resistivity coefficients. The solutions are parameterized with respect to a phenomenological altitude-dependent anomaly coefficient A and are compared with an observed storm time electron temperature profile above Chatanika. The calculated temperature profile for the classical case (A = 1) disagrees considerably with the measured profile over most of the altitude range up to 450 km. It is shown that an anomaly coefficient with a sharp peak of the order of 10,000 centered around the F2 peak is consistent with observations.

Fontheim, E. G.↗
NASA NTRS1976

Cooling and recombination processes in cometary plasma

The ion electron plasma in comets is examined for cooling processes which result from its interactions with the neutral coma. A cometary coma model is formulated that is composed predominantly of H2O and its decomposition products where electrons are cooled in a variety of processes at rates varying with energy. It is shown that solar plasma plus accumulated cometary ions and electrons is affected very strongly as it flows into the coma. The electrons are rapidly cooled and all but some 10% of the ions undergo charge exchange. Photodissociation of H2O is assumed where ion electron recombination is the dominant loss process.

Wallis, M. K.↗