On the energy transfer between flows and turbulence in the plasma boundary of fusion devices

The energy transfer between perpendicular flows and turbulence has been investigated in the JET plasma boundary region. The energy transfer from DC flows to turbulence, directly related with the momentum flux (e.g. 〈v˜θv˜r〉) and the radial gradient in the flow, can be both positive and negative in the proximity of sheared flows. The direct computation of the turbulent viscosity gives values comparable to the anomalous particle diffusivitiy (in the order of 1 m2/s). Furthermore, this energy transfer rate is comparable with the mean flow kinetic energy normalized to the correlation time of turbulence, implying that this energy transfer is significant. These results show, for the first time, the dual role of turbulence as a damping (eddy viscosity) and driving of flows in fusion plasmas emphasizing the important role of turbulence to understand perpendicular dynamics in the plasma boundary region of fusion plasmas.