Self-Consitent Computation of Transport Barrier Formation by Fluid Drift Turbulence in Tokamak Geometry

BY FLUID DRIFT TURBULENCE IN TOKAMAK GEOMETRY (1) Computations of turbulence from the electromagnetic gyro uid model are performed in a ux surface geometry represen ting the actual MHD equilibrium of the ASDEX Upgrade edge ux surfaces.The transition to ideal ballooning seen in simple geometries as the plasma beta rises is suppressed, lea ving the transport at quantitatively realistic levels.Computations for core parameters at half-radius geometry sho w signi cant contribution due to the nite beta electron dynamics, possibly remo ving the standard ITG threshold.(2) Strong in ward vorticity transport in edge turbulence, resulting from ion diamagnetic o ws, ma y lead to a build up of mean ExB v orticity fast enough to cause an H-mode transition.(3) F riction of mean ion o ws against neutrals involves both toroidal and poloidal ow componen ts, leading to a nite radial current due to a given ExB pro le even with zero poloidal rotation.