Re-forming supercritical quasi-parallel shocks 2. Mechanism for wave generation and front re-formation

Journal Article · Thu Nov 01 04:00:00 EST 1990 · Journal of Geophysical Research; (United States)

DOI:https://doi.org/10.1029/JA095iA11p18821· OSTI ID:5131612

Winske, D; Thomas, V A ^[1]; Omidi, N; Quest, K B ^[2]

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1. Los Alamos National Lab., NM (United States)
2. Univ. of California, San Diego (United States)

One-dimensional hybrid simulations of quasi-parallel shocks and two stream interactions are carried out in order to study the mechanism by which large-amplitude electromagnetic waves are generated at the shock and maintained in a quasi-steady manner. It is concluded that a resonant interaction at the interface between the incoming ions and the heated downstream ions (interface instability) is the most likely source of the waves that ultimately comprise the quasi-parallel shock. The effect of the generation of these waves at the shock transition results locally in a nonsteady shock ramp, which propagates downstream with respect to the average shock position and is then replaced by a new steepened ramp at the original front position. This process is complicated by several competing effects. First, backstreaming ions excite the beam cyclotron resonant instability at wavelengths longer than those generated at the shock interface with gives rise to compressive upstream perturbations that are then carried into the shock and interact with the shock-generated waves. Second, the re-formation process sometimes leads to the appearance of cold dense ion beams just upstream from the shock which gyrate in the upstream magnetic field to produce local density enhancements that have some effect on where the new shock front forms. Third, whistlers at wavelengths shorter than the waves associated with the reformation process are also present that can scatter the backstreaming ions into a hotter, more diffuse population. In order to separate these various processes, numerical experiments involving quasi-parallel shocks and the interaction of two plasma streams have been carried out for various upstream parameters.

• OSTI ID: 5131612
• Journal Information: Journal of Geophysical Research; (United States), Journal Name: Journal of Geophysical Research; (United States) Vol. 95:A11; ISSN 0148-0227; ISSN JGREA
• Country of Publication: United States
• Language: English

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71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
75 CONDENSED MATTER PHYSICS
SUPERCONDUCTIVITY AND SUPERFLUIDITY
BEAMS
CHARGED PARTICLES
COMPUTERIZED SIMULATION
ELECTROMAGNETIC RADIATION
FLUID MECHANICS
HYDRODYNAMICS
INSTABILITY
INTERACTIONS
ION BEAMS
IONS
MAGNETIC FIELDS
MAGNETOHYDRODYNAMICS
MECHANICS
NOISE
ONE-DIMENSIONAL CALCULATIONS
PLASMA INSTABILITY
RADIATIONS
RADIO NOISE
RADIOWAVE RADIATION
REFLECTION
SHOCK WAVES
SIMULATION
WAVE PROPAGATION
WHISTLERS