Engineering topics

Schriver, D.

Publications and source records attributed to Schriver, D..

20 records · Page 2

NASA NTRS1988

A simulation study of broadband electrostatic noise in the presence of ionospheric electrons

Ion beams have been observed flowing along magnetic field lines in the earth's plasma sheet boundary layer and are believed to generate intense electrostatic wave activity known as broadband electrostatic noise. Cold electrons of ionospheric origin have also been observed in this same region and it has been shown that the addition of these cold electrons modifies substantially the plasma wave dispersion properties. With cold electrons present, four instabilities can be excited: (1) ion acoustic, (2) electron acoustic, (3) beam resonant, and (4) Buneman two stream. These instabilities can generate waves with large growth rates at frequencies consistent with broadband electro-static noise. Using computer simulations, consideration is given to the wave energy frequency spectra generated by these instabilities, as well as cold electron heating and nonlinear effects on the ion beam.

Schriver, D.↗

NASA NTRS1986

Computer simulations of electromagnetic cool ion beam instabilities

Electromagnetic ion beam instabilities driven by cool ion beams at propagation parallel or antiparallel to a uniform magnetic field are studied using computer simulations. The elements of linear theory applicable to electromagnetic ion beam instabilities and the simulations derived from a one-dimensional hybrid computer code are described. The quasi-linear regime of the right-hand resonant ion beam instability, and the gyrophase bunching of the nonlinear regime of the right-hand resonant and nonresonant instabilities are examined. It is detected that in the quasi-linear regime the instability saturation is due to a reduction in the beam core relative drift speed and an increase in the perpendicular-to-parallel beam temperature; in the nonlinear regime the instabilities saturate when half the initial beam drift kinetic energy density is converted to fluctuating magnetic field energy density.

Gary, S. P.↗