Simulation of parametric instability effects in a beam plasma system
- Univ. of Iowa, Iowa City, IA (United States)
An energetic electron beam produces large amplitude resonant plasma oscillations which can parametrically decay into growing nonresonant electron and ion waves if ion dynamics are included. A similar parametric instability occurs in a plasma driven by a high frequency external electric field. A two-specie particle simulation study of beam generated parametric instabilities is presented and the results compared with corresponding one-specie beam and external field simulations. For low beam densities the individual nonresonant modes grow approximately at the rates predicted by parametric instability theory. This growth eventually causes the resonant plasma oscillations to decay exponentially at a rate proportional to the original parametric growth rate. fe(v) develops suprathermal tails which eventually lead to a stable non-Maxwellian plasma with a field energy spectrum Wk approximately k-2 as seen in external field simulations. The velocity diffusion coefficient has been measured from test particle dynamics, and beam plasmas driven by an external field have been simulated. Also, the possible role of the parametric instability in stabilizing the beam against deceleration has been studied, and the inclusion of parametric threshold effects lead to more stringent requirements for parametric stabilization than had been previously assumed. The consequences for several astrophysical and laboratory plasma systems are discussed.
- Research Organization:
- Univ. of Iowa, Iowa City, IA (United States). Dept. of Physics and Astronomy
- Sponsoring Organization:
- US Energy Research and Development Administration (ERDA)
- NSA Number:
- NSA-33-025645
- OSTI ID:
- 4028984
- Report Number(s):
- COO--2059-51
- Country of Publication:
- United States
- Language:
- English
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