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P: Plasmaphysik
P 23: Theorie (Poster)
P 23.2: Poster
Tuesday, March 16, 1999, 16:30–19:00, PY
Electromagnetic Gyrofluid Turbulence in Realistic Tokamak Geometry — •B. Scott — Max-Planck-Institut f"ur Plasmaphysik, EURATOM Assoziation, D-85748 Garching
A finite difference model of the gyrofluid equations has been extended to include the effects of self-consistent, electromagnetic electron dynamics parallel to the magnetic field. The resulting dynamical system represents fluidlike ExB turbulence with arbitrary ion gyroradius exciting pressure disturbances in planes perpendicular to the magnetic field, with the planes tied together by dissipative parallel Alfvén dynamics — an extension of drift Alfvén turbulence to the collisionless, hot-ion regime. The turbulence is computed in globally consistent flux tube geometry, with the magnetic flux surface form resulting from a computed equilibrium closely modelling the ASDEX Upgrade tokamak. One important result is that passing electrons play their role in the Alfvén dynamics even deep in the plasma core in modern tokamaks, due to the finite beta regime (of order 10−2) which allows resonance between Alfvén and drift waves. The character of edge turbulence is relatively unchanged by the extra finite ion gyroradius effects, due to its relatively large scale (of order 10 gyroradii). There is no change in basic character of tokamak turbulence moving from edge to core, due to the Alfvén dynamics; inferred turbulent diffusivities rise towards the edge solely due to the increasing parallel/perpendicular scale ratio.