Flow generation due to plasma-wall interaction in reversed-field pinches

In the Reversed-Field Pinch (RFP) experiment ZT-40M, line density disturbances near the plasma edge were observed (JACOBSON et al., 1983) to have an apparent group velocity roughly of the order of the ion thermal speed in the direction antiparallel to the toroidal current. A possible explanation of this phenomenon is presented that relies on the experimentally observed pump-out process by showing that mass flow in an annulus of at least several centimeters near the plasma edge arises as the result of thermal ion momentum transfer to the wall.