Electric Field and Poloidal Rotation in the Turbulent Edge Plasma of the T-10 Tokamak

Abstract

The dynamics of turbulent edge plasma in the T-10 tokamak is simulated numerically by solving reduced nonlinear MHD equations of Braginskii’s two-fluid hydrodynamics. It is shown that the poloidal plasma velocity is determined by the combined effect of two forces: the turbulent Reynolds force F_R and the Stringer–Winsor geodesic force F_SW, which is associated with the geodesic acoustic mode of the total plasma pressure \(\left\langle {p{\text{sin}}\theta } \right\rangle \). It follows from the simulation results that the F_R and F_SW forces are directed oppositely and partially balance one another. It is shown that, as the electron temperature increases, the resulting balance of these forces changes in such a way that the amplitude of the poloidal ion flow velocity and, accordingly, the electrostatic potential \({{\phi }_{0}}(r,t)\) decrease. As the plasma density increases, the “driving forces” of turbulence (the dn₀/dr and dp₀/dr gradients) also increase, while dissipation due to the longitudinal current decreases, which results in an increase in the amplitude of turbulent fluctuations and the Reynolds force F_R. On one hand, the force F_SW increases with increasing plasma density due to an increase in the pressure \(\left\langle {p{\text{sin}}\theta } \right\rangle \); however, on the other hand, it decreases in view of the factor 1/n₀. As a result, the net force driving poloidal rotation increases, which leads to the growth of the plasma potential. Both under electron-cyclotron resonance heating and in regimes with evolving plasma density, the results of numerical simulations qualitatively agree with experimental data on the electrostatic potential of the T-10 plasma.