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Abstract. We report on fluid, gyrofluid and gyrokinetic numerical studies of edge turbulence in both tokamak and stellarator geometry, regarding both its physical character and its interaction with the flux surface averaged (``zonal'') ExB flows and magnetic fields. We run several electromagnetic models under drift ordering in globally consistent flux tube geometry: three fluid models of increasing complexity, a gyrofluid model, and a collisionless gyrokinetic phase space continuum model. All treat both electron and ion dynamics. The fluid models employ a Landau closure for the parallel heat fluxes, which are treated dynamically. The fluid and gyrofluid models all run at arbitrary collisionality. We find turbulence of drift wave and ion temperature gradient mode (ITG) character at all parameters of interest to experiment. Although an ExB shear layer imposed by the equilibrium is effective in suppressing turbulence, a strong enough shear layer to account for the L-to-H confinement transition is never self-generated by the turbulence in three dimensions. The turbulence correlation length is more sensitive to the equilibrium ExB shear than to any other parameter. Zonal fields in contrast to zonal flows have little effect below the ideal MHD boundary. Similar results are found for both stellarator and tokamak geometry, in agreement with experimentally observed universality of turbulence.
IAEA 2001
