Impact of stochastic magnetic fields on plasma rotation and radial electric fields in the plasma edge of the tokamak TEXTOR

In this contribution we report on spectroscopic measurements of plasma rotation and the radial electric field in the plasma boundary under the operation of the dynamic ergodic divertor in TEXTOR. Under the influence of the stochastic magnetic field we observe an increase of both poloidal and toroidal rotation of carbon nuclei into ion-diamagnetic drift/co-current direction. With static magnetic perturbation the electric field in the ergodic region increases by 10 kV/m and becomes positive. Application of dynamic perturbation leads to a comparable change of the rotation, independent of the direction of the rotation of the DED field and only depending on the degree of ergodization. We introduce a model to explain the experimental findings by the onset of transverse currents in the ergodic region and a subsequent torque onto the plasma.