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Ossakow, S. L.

Publications and source records attributed to Ossakow, S. L..

6 records
All sourcesNASA NTRSDOE OSTI
NASA NTRS1992

A low-altitude mechanism for mesoscale dynamics, structure, and current filamentation in the discrete aurora

The 2D nonlinear evolution of the ionization-driven adiabatic auroral arc instability is studied. We find: (1) the adiabatic auroral arc instability can fully develop on time scales of tens to hundreds of seconds and on spatial scales of tens to hundreds of kilometers; (2) the evolution of this instability leads to nonlinear 'hook-shaped' conductivity structures: (3) this instability can lead to parallel current filamentation over a wide range of scale sizes; and (4) the k-spectra of the density, electric field, and parallel current develop into inverse power laws in agreement with satellite observations. Comparison with mesoscale auroral phenomenology and current filamentation structures is made.

Keskinen, M. J.↗
NASA NTRS1989

d.c. electric field stabilization of plasma fluctuations due to a velocity shear in the parallel ion flow

Consideration is given to the suggestion by Basu and Coppi (1988, 1989) that the DE-2 observations of broadband turbulence associated with sheared ion flows can be explained by electrostatic waves driven by a sheared ion flow along the magnetic field. It is pointed out that such a theory ignores the stronger shear in the ion flow transverse to the magnetic field, and that, when this shear is taken into account, the modes described by Basu and Coppi are easily destabilized. The theory of Basu and Coppi is shown to break down even when the shear in the parallel flow exceeds the shear in the transverse flow.

Ganguli, G.↗
NASA NTRS1985

Theory of the current-driven ion cyclotron instability in the bottomside ionosphere

A comprehensive treatment of the theory of electrostatic ion cyclotron instability in the collisional bottomside ionosphere is given. The linear dispersion relations for the ion cyclotron instability (electron and ion collisions) are derived. Analytical solutions to the dispersion relation are obtained in three limits: collisionless; weakly collisional; and collisional. In addition, the linear dispersion relation is solved numerically, using parameters typical of the high-latitude bottomside ionosphere. It is pointed out that the linear growth rates in the bottomside collisional regime can be of the same order as the corresponding topside collisionless growth rates. A nonlinear saturation mechanism for the electrostatic ion cyclotron instability is proposed on the basis of Dupree's (1966) resonance broadening theory.

Satyanarayana, P.↗
NASA NTRS1978

Ionospheric modification - An initial report on artificially created equatorial Spread F

A numerical simulation code for investigating equatorial Spread F in the collisional Rayleigh-Taylor regime is utilized to follow the evolution of artificial plasma density depletions injected into the bottomside nighttime equatorial F region. The 70 km diameter hole rapidly rises and steepens, forming plasma density enhancements at altitudes below the rising hole. The distribution of enhancements and depletions is similar to natural equatorial Spread F phenomena, except it occurs on a much faster time scale. These predictions warrant carrying out artificial injection experiments in the nighttime equatorial F region.

Ossakow, S. L.↗
NASA NTRS1973

Proton scattering in the region near the earth's bow shock.

Lockheed spectrometer data from orbits 1 through 20 of Ogo 5 are used to study proton scattering near the bow shock. Correlative UCLA fluxgate magnetometer data from the satellite are used to complete motion studies of the bow shock when spectrometer data are missing. Thirty-eight analyzable sets of multiple shock crossings show 358 shock encounters ranging from 10 to 22 earth radii and spanning sun-earth-satellite angles from 30 to 90 deg. Gross features of the study show that the location and shape of the bow shock are in good agreement with the hydrodynamic model of the bow shock.

Ossakow, S. L.↗