NEOCLASSICAL QUASI-LINEAR TRANSPORT-THEORY OF FLUCTUATIONS IN TOROIDAL PLASMAS - FURTHER CONSIDERATIONS

The effects of the radial electric field Er on fluctuation-induced transport fluxes and the fluctuation spectrum in toroidal plasmas are further studied to clarify the ideas originally developed in an earlier paper [Phys. Fluids 31, 2249 (1988)]. A specific tokamak example is employed in the discussion. It is found that even in the presence of fluctuations, the parallel flow in tokamaks is damped by the neoclassical viscosity on a time scale of the order of νii-1, with νii the collision frequency. The toroidal flow is damped by the anomalous ion viscosity on a time scale of the order of the confinement time. The radial electric field always has an effect on the fluctuation spectrum and fluctuation-induced transport fluxes in tokamaks except when d(E rq/r)/dr = 0 (where q is the safety factor and r is the minor radius) if the radial dependence of the toroidal magnetic field is neglected by considering the invariant property of the drift kinetic equation when there is a change in Er. The condition implies the rigid-body toroidal rotation associated with ExB drift, with E (B) the electric (magnetic) field. The fact that the fluctuation-induced transport fluxes can depend on Er through the fluctuation spectrum and the thermodynamic force does not contradict their intrinsic ambipolarity property. The results are shown to be invariant under Galilean transformation. © 1990 American Institute of Physics.