Edge transport modulation by coherent shear flows

Different from the core, in the transitional core/edge regime a rich variety of distinct radially and poloidally coherent flow structures have been found by numerical and analytic studies, ranging from solitary propagating zonal flows to sinusoidal structures with definite radial wavenumber. Toward the edge, the fluctuating flows get weaker until the coherent component of the flows vanishes completely, which is analytically analogous to the Bose-Einstein phase transition. The coherent flow structures strongly modulate the transport via wave-kinetic effects. The clear signature and the transport relevance of the coherent flows in the transitional regime make them an ideal target for experimental investigation. (author)