Plasma edge modification induced by electrode biasing in RFX

Positive and negative edge biasing experiments induced by electrodes have been performed in the reversed field pinch experiment RFX at 300-400 kA toroidal plasma current; in both conditions the edge radial electric field has been modified. A model, based on the Ohm's law and the momentum balance equation, has been developed in analogy to tokamaks to interpret the observed values of the toroidal flow velocity and its modification due to the electrode operation. Anomalous perpendicular viscosity due to anomalous particle diffusion has been assumed and the equations have been written in cylindrical co-ordinates. Preliminary results of a numerical code based on this model show a good agreement with the experimental data without biasing and justify the toroidal velocity variations induced by the electrode current.