Effect of a transition between regular and stochastic electron motion on the evolution of an obliquely propagating Langmuir wave
The evolution of an obliquely propagating Langmuir wave is considered, with emphasis on determining the effect of a transition between regular and stochastic electron motion. The wave has three distinct evolution regimes, whose locations in parameter space depend roughly on the relative sizes of the linear damping rate ..gamma.., the electron bounce frequency ..omega../sub b/ and the electron cyclotron frequency ..cap omega... When ..omega../sub b/<..gamma.., the wave is in the linear regime and simply damps away. When ..gamma..<..omega../sub b/<..cap omega.., the wave evolution is dominated by regular, trapped electron motion in individual resonances. It is shown that when the propagation angle increases to about 14/sup 0/, the trapping oscillations present in parallel propagating waves disappear due to phase mixing of the different bounce frequencies. When ..gamma..<..cap omega..<..omega../sub b/, the wave evolution is dominated by stochastic particle motion from resonance to resonance. It is shown that when a transition is made from the trapping to the stochastic regime, the final (t = infinity) wave amplitude significantly decreases, due to the increased ability of the electrons to take energy from the wave. Finally, simulation results which verify key aspects of the theory are reported.
- Research Organization:
- Laboratory for Plasma and Fusion Energy Studies, University of Maryland, College Park, Maryland 20742
- DOE Contract Number:
- AM03-76SF00010
- OSTI ID:
- 6482702
- Journal Information:
- Phys. Fluids; (United States), Journal Name: Phys. Fluids; (United States) Vol. 26:3; ISSN PFLDA
- Country of Publication:
- United States
- Language:
- English
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