Some nonlinear properties of drift-cyclotron modes

Journal Article · Sat May 01 04:00:00 EDT 1982 · Phys. Fluids; (United States)

DOI:https://doi.org/10.1063/1.863812· OSTI ID:5419059

Cohen, B I; Maron, N; Smith, G R

The nonlinear evolution of the drift-cyclotron instability has been investigated by means of analytical perturbation theory and computer simulations with a particle-fluid hybrid code. The nonlinear modification of the electrostatic ion response in the presence of a single drift-cyclotron mode is calculated. It is determined that a nonlinear shift in the effective ion cyclotron frequency can stabilize long-wavelength modes (ka/sub i/approx.N/kappaa/sub i/, ..omega..roughly-equal..omega../sub asterisk/roughly-equalN..omega../sub c/i, N = +- 1, +- 2, ...) at fairly small amplitudes of the electrostatic potential Vertical Barephi/T/sub i/Vertical Barapprox.(m/sub e//m/sub i/+..omega../sup 2//sub c/i/ ..omega../sup 2//sub p/i)/sup 1/2/kappaa/sub i/, where ..omega../sub asterisk/ is the ion diamagnetic drift frequency, a/sub i/ is the ion gyroradius, T/sub i/ is the ion temperature, and kappa/sup -1/ is the density-gradient scale length. These saturated states exhibit nonlinear oscillations, and analysis indicates that these states are stable to perturbations arising from other long-wavelength drift-cyclotron modes. A shift of the ion cyclotron frequency is not the dominant nonlinear feature in the case of more unstable short-wavelength modes (ka/sub i/approx.(m/sub e//m/sub i/+..omega../sup 2//sub c/i /..omega../sup 2//sub p/i)/sup -1/2/, ..omega..roughly-equalN..omega../sub c/iapprox...omega../sub asterisk//2), and the nonlinear ion response is much more difficult to calculate. Simulations indicate that the short-wavelength modes eventually trap ions, as has been seen in previous simulations of ion cyclotron instabilities and the closely related lower-hybrid drift instability.

• Research Organization: Lawrence Livermore National Laboratory, University of California, Livermore, California 94550
• OSTI ID: 5419059
• Journal Information: Phys. Fluids; (United States), Journal Name: Phys. Fluids; (United States) Vol. 25:5; ISSN PFLDA
• Country of Publication: United States
• Language: English

Related Subjects

70 PLASMA PHYSICS AND FUSION TECHNOLOGY
700107 -- Fusion Energy-- Plasma Research-- Instabilities
700108* -- Fusion Energy-- Plasma Research-- Wave Phenomena
COMPUTERIZED SIMULATION
CYCLOTRON INSTABILITY
DRIFT INSTABILITY
INSTABILITY
NONLINEAR PROBLEMS
PERTURBATION THEORY
PLASMA INSTABILITY
PLASMA MICROINSTABILITIES
SIMULATION