Radial profiles of the poloidal velocity of fluctuations and parallel flows have been investigated in the plasma boundary region of the JET tokamak. It has been observed that sheared poloidal and parallel flows are linked. The shear in the poloidal flow is close to the inverse time of the correlation of fluctuations (dv?/dr ~ 1/t) and the shear in the parallel flow is close to d vparallel/dr ~ cs /Ln, where cs and Ln are sound speed and the density scale length, suggesting a proximity to the threshold of Kelvin-Helmhotz instabilities.
The dynamical coupling between turbulent transport and parallel flows has also been investigated, using an experimental set-up which allows to measure simultaneously both the electrostatic turbulent transport and the parallel Mach number. Probability Density Functions (PDFs) for parallel flows and transport are quite different. Whereas PDFs for transport show clear non-gaussian features and large and sporadic burst, PDFs of parallel flows look, at first sight, rather gaussian. The results show that turbulent transport and parallel flows are dynamically coupled. The expected value of parallel flows significantly increases as the size ExB turbulent transport events gradient increases. The interplay between the statistical properties of turbulent transport and parallel flows has been investigated at different time scales. As time scale increases the PDF of transport is mainly dominated by outwards transport events and the dynamical coupling between transport and parallel flows becomes stronger. This result suggests that low frequencies have a dominant effect on the link between parallel flows and turbulent transport. On the basis of the present results, we conclude that the bursty and strongly nongaussian behaviour of turbulent transport is strongly coupled with fluctuations in parallel flows. This dynamical coupling reflects that parallel flows are, at least partially, driven by turbulence mechanisms. Considering that significant plasma turbulence has been observed both in the edge and core plasma regions, the present results might have a strong impact in our understanding of parallel momentum transport in fusion plasmas. In particular, these findings suggest that turbulent mechanism is an ingredient to explain the generation of parallel flows in the plasma boundary region [1] and the onset of spontaneous rotation in tokamak plasmas [2,3].

[1] S.K. Erents, A.V. Chankin, G.F. Matthews and P.C. Stangeby, Plasma Phys. Control. Fusion 42 (2000) 905.
[2] J.E. Rice, J.A. Goetz, R.S. Granetz et al., Phys. of Plasmas 7 (2000) 1825.
[3] B. Coppi, Nuclear Fusion 42 (2002) 1.