On the Toroidal Plasma Rotations Induced by Lower Hybrid Waves
Authors: Xiaoyin Guan, Hong Qin, Jian Liu and Nathaniel J. Fisch
Abstract:
A theoretical model is developed to explain the plasma rotations induced by lower hybrid waves
in Alcator C-Mod. In this model, torodial rotations are driven by the Lorentz force on the bulk
electron flow across flux surfaces, which is a response of the plasma to the resonant-electron
flow across flux surfaces induced by the lower hybrid waves. The flow across flux surfaces of the resonant
electrons and the bulk electrons are coupled through the radial electric fi eld initiated by the resonant
electrons, and the friction between ions and electrons transfers the toroidal momentum to ions
from electrons. An improved quasilinear theory with gyrophase dependent distribution function is
developed to calculate the perpendicular resonant-electron flow. Toroidal rotations are determined
using a set of fluid equations for bulk electrons and ions, which are solved numerically by a fi nite-
difference method. Numerical results agree well with the experimental observations in terms of
flow pro file and amplitude. The model explains the strong correlation between torodial flow and
internal inductance observed experimentally, and predicts both counter-current and co-current
flows, depending on the perpendicular wave vectors of the lower hybrid waves.
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Submitted to: Physics of Plasmas (November 2012)
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Download PPPL-4831 (pdf 691 KB 22 pp)
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