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(TH1/5) Self-Consistent Computation of Transport Barrier Formation by Fluid Drift Turbulence in Tokamak Geometry

B. Scott, F. Jenko, A. Peeters, A. C-Y. Teo

Max Planck Institut für Plasmaphysik, Euratom Association, D-85748 Garching bei München, Germany

Abstract.  (1) Computations of turbulence from the electromagnetic gyrofluid model are performed in a flux surface geometry representing the actual MHD equilibrium of the ASDEX Upgrade edge flux surfaces. The transition to ideal ballooning seen in simple geometries as the plasma beta rises is suppressed, leaving the transport at quantitatively realistic levels. Computations for core parameters at half-radius geometry show significant contribution due to the finite beta electron dynamics, possibly removing the standard ITG threshold. (2) Strong inward vorticity transport in edge turbulence, resulting from ion diamagnetic flows, may lead to a build up of mean ExB vorticity fast enough to cause an H-mode transition. (3) Friction of mean ion flows against neutrals involves both toroidal and poloidal flow components, leading to a finite radial current due to a given ExB profile even with zero poloidal rotation.

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