Effect of density variations along ion drift trajectories on the poloidal and toroidal rotation velocities of a collisionless tokamak plasma

The effect of plasma density variations along ion drift trajectories on the ion velocity distribution function at a given point on a tokamak magnetic surface is studied. The observed distortion of the distribution function can be interpreted as a poloidal (or toroidal) plasma rotation that is additional to the neoclassical rotation. Due to this additional rotation, the velocity of the toroidal plasma rotation is different on the low-and high-field sides of the same magnetic surface. In the case of large ion density gradients, the poloidal rotation velocity on the same magnetic surface can have different signs at different poloidal angles.