Gyrokinetic Studies of Turbulence, Equilibrium, and Flows in the Tokamak Edge

Full text: We report on the theory and computation of gyrokinetic turbulence in the tokamak edge. A new formulation of the gyrokinetic Lagrangian for the strong E x B-flow regime has been found which differs from the previous version by a Lie transform. Correspondence to δf forms and to nonlinear reduced MHD was shown. This is the basis for our full f phase-space computational model FEFI. The δf model dFEFI, derived from this, in turn, is used in a comprehensive parameter study of tokamak edge turbulence in which energetic processes are quantitatively diagnosed. In this kinetic representation, edge turbulence is found to be much more sensitive to sheared flows than in previous gyrofluid studies. We explore the self consistent MHD/neoclassical equilibrium with FEFI, including the development of bootstrap flows and currents as functions of collisionality, and the collisionless control case with these effects not occurring. In both collisional and collisionless cases the conservation of particles, energy, canonical momentum, and entropy is of order 10-4. We also present the status of experiment/simulation comparisons and simulated reflectometry of edge/SOL turbulence, and ongoing gyrofluid studies of ELM crash scenarios, including the influence of the bootstrap current in an edge pedestal model on both the initial instability and the resulting turbulence. These studies and findings are centrally relevant to further understanding of the H-mode and pressure profile pedestal in large tokamaks. (author)