Relaxation oscillations induced by amplitude-dependent frequency in dissipative trapped electron mode turbulence

Journal Article · Thu Dec 01 00:00:00 EST 1994 · Physics of Plasmas; (United States)

DOI:https://doi.org/10.1063/1.870868· OSTI ID:7093400

Terry, P W; Ware, A S; Newman, D E ^[1]

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1. Department of Physics, University of Wisconsin---Madison, Madison, Wisconsin 53706 (United States)

A nonlinear frequency shift in dissipative trapped electron mode turbulence is shown to give rise to a relaxation oscillation in the saturated power density spectrum. A simple non-Markovian closure for the coupled evolution of ion momentum and electron density response is developed to describe the oscillations. From solutions of a nonlinear oscillator model based on the closure, it is found that the oscillation is driven by the growth rate, as modified by the amplitude-dependent frequency shift, with inertia provided by the memory of the growth rate of prior amplitudes. This memory arises from time-history integrals common to statistical closures. The memory associated with a finite time of energy transfer between coupled spectrum components does not sustain the oscillation in the simple model. Solutions of the model agree qualitatively with the time-dependent numerical solutions of the original dissipative trapped electron model, yielding oscillations with the proper phase relationship between the fluctuation energy and the frequency shift, the proper evolution of the wave number spectrum shape and particle flux, and a realistic period.

• DOE Contract Number: FG02-89ER53291
• OSTI ID: 7093400
• Journal Information: Physics of Plasmas; (United States), Vol. 1:12; ISSN 1070-664X
• Country of Publication: United States
• Language: English

Related Subjects

70 PLASMA PHYSICS AND FUSION TECHNOLOGY
TOKAMAK DEVICES
TRAPPED ELECTRONS
TURBULENCE
ELECTRON DENSITY
FREQUENCY DEPENDENCE
INSTABILITY GROWTH RATES
OSCILLATIONS
RELAXATION
CLOSED PLASMA DEVICES
ELECTRONS
ELEMENTARY PARTICLES
FERMIONS
LEPTONS
THERMONUCLEAR DEVICES
700340* - Plasma Waves
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