Generation of sheared poloidal flows via Reynolds stress and transport barrier physics

A view of the latest experimental results and progress in the understanding of the role of poloidal flows driven by fluctuations via Reynolds stress is given. Reynolds stress shows a radial gradient close to the velocity shear layer location in tokamaks and stellarators, indicating that this mechanism may drive significant poloidal flows in the plasma boundary. Observation of the generation E x B sheared flows via Reynolds stress at the ion Bernstein resonance layer has been noticed in toroidal magnetized plasmas. The experimental evidence of sheared E x B flows linked to the location of rational surfaces in stellarator plasmas might be interpreted in terms of Reynolds stress sheared driven flows. These results show that E x B sheared flows driven by fluctuations can play an important role in the generation of transport barriers. © 2000 IOP Publishing Ltd.