Shear flows generated by plasma turbulence and their influence on transport

The interplay between sheared E x B mean flows and turbulence is reviewed while highlighting the common features observed in three different magnetic configurations: tokamak, stellarator and reversed field pinch. By comparing results from different experiments spanning a wide range of parameters, a universal relationship between the small scales of plasma turbulence and the large scales of the plasma mean flow is observed. In particular the generation of E x B flows by plasma turbulence in the edge region of fusion experiments is addressed by discussing the driving and damping action exerted by turbulence. In this context recent measurements of Reynolds stress and estimates of plasma viscosity are presented. The energy transfer from turbulence to mean flow is also addressed on presenting the latest experimental results. Finally the findings are discussed highlighting the elements supporting a turbulence self-regulation process.