ISSN:
1089-7674
Source:
AIP Digital Archive
Topics:
Physics
Notes:
The issues concerning the response of a plasma, at or near a singular surface, to a magnetic perturbation with a phase velocity different from the plasma flow velocity, are important for a number of phenomena. Among these are ideal and nonideal magnetohydrodynamic stability of plasmas with shear flow or a flow relative to a resistive wall, sensitivity of rotating plasma to field errors, and the "locked mode'' phenomenon. Models for the singular surface response have been tested against results from "magnetic braking'' experiments in DIII-D [R. J. La Haye et al., Nucl. Fusion 32, 2119 (1992)]. Previous models are found unable to account for all of the experimental observations. A new heuristic nonlinear model presented in the paper may account for the observations. A key element in the model is turbulence developed at the singular surface; the turbulence is assumed driven by the singular layer dissipation and is assumed to impede the singular current through an anomalous resistivity. When the perturbation amplitude is sufficiently large, a positive feedback mechanism exists, since in the regime of interest, dissipation increases with decreasing singular current. For small perturbation amplitudes this mechanism is not operative so that previous models for the response may be valid. © 1996 American Institute of Physics.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1063/1.872013
