Toroidal flows and radial electric field during the formation of an internal transport barrier in a tokamak plasma

Toroidal flows without momentum injection and the radial electric field in a tokamak plasma with impurity ions are theoretically investigated. It is found that the radial electric field is generated by the polarization current due to the time-varying diamagnetic drift, which is balanced by the polarization current due to the time-varying E × B drift in toroidal geometry. Toroidal flows are generated by the polarization current for fuel ions and impurity ions in opposite directions, following the toroidal angular momentum conservation law. The predicted toroidal flows are consistent with the experimental results related to the formation of an internal transport barrier.