Showing papers by "Mary K. Hudson published in 1988"

Linear stability of the H+ ‐ O+ two‐stream interaction in a magnetized plasma

Abstract: The Bergman and Lotko (1986) analysis of the linear stability of the H(+) - O(+) two-stream interactions for parallel propagating wave modes is extended to an analysis of the stability of wave modes that propagate at an angle to the terrestrial magnetic field. The analaysis provides an insight into the manner in which the oblique modes linearly couple and become unstable; the conditions under which the particular couplings are important; the qualitative behavior of the frequency, wave vector, and growth rate of the most unstable mode; and the changes to these introduced by finite ion temperatures. Consideration is also given to the relative importance of obliquely propagating and parallel propagating waves for the condition when the velocity difference between two ion beams is below the upper limit.

Dynamics of localized ion‐acoustic waves in a magnetized plasma

Abstract: The evolution of negative potential pulses in a magnetized plasma is studied. A three‐dimensional (3‐D) nonlinear ion‐acoustic wave equation, including nonstationary effects of reflected electrons, has been derived from the Poisson–Vlasov equations with uniform magnetic field. In the low temperature limit, the equation is the Zakharov–Kuznetsov equation. Computer simulations of 1‐D and 2‐D versions of the equation have been performed. The studies show that a negative potential pulse can be enhanced by drifting electrons. The growing pulse develops asymmetrically with an oscillatory precursor and a local potential jump resembling the early phase of weak double layer formation. Two‐dimensional pulses also show different scale lengths along the magnetic field and in the transverse dimension. Comparisons are made with results from particle simulations and spacecraft observations.

Simulations of active ion injection experiments on ARCS 3

Abstract: The ARCS 3 sounding rocket experiment used two argon guns oriented parallel and perpendicular to the geomagnetic field. The parameters of this experiment have been used in a series of particle simulations in order to interpret ion beam interaction with the multispecies ionospheric plasma. Along with the lower hybrid mode between the electron and the hydrogen gyrofrequencies, ion-ion hybrid modes between the hydrogen and helium gyrofrequencies and between the helium and oxygen gyrofrequencies are identified in the simulations. Besides these cold plasma modes, warm Bernstein modes of the respective ion species are identified. The parallel argon beam injections excite lower hybrid waves perpendicular to the magnetic field because of the finite thermal spread of the parallel beam. Perpendicular ion heating of background hydrogen, helium, and oxygen is comparable in the simulations. Comparisons are made with the wave and particle data from the ARCS 3 rocket experiment.