Plasma rotation in stellarators and rippled tokamaks

The general equations obtained previously by the author for the time evolution of the ambipolar electric field and longitudinal plasma velocity in arbitrary toroidal magnetic confinement systems are used here to find an explicit expression for the longitudinal viscous force and to derive equations for the plasma rotation velocities in the poloidal and toroidal directions in rippled tokamaks and toroidal stellarators. It is shown, in particular, that the relaxation times of the poloidal and toroidal plasma rotation are independent of the magnetic field magnitude and are governed by the collision frequency and the toroidal (or helical) ripple amplitude.