Gyrokinetic turbulence simulations at high plasma beta

Electromagnetic gyrokinetic turbulence simulations employing Cyclone Base Case parameters are presented for beta values up to and beyond the kinetic ballooning threshold. The beta scaling of the turbulent transport is found to be linked to a complex interplay of linear and nonlinear effects. Linear investigation of the kinetic ballooning mode is performed in detail, while nonlinearly, it is found to dominate the turbulence only in a fairly narrow range of beta values just below the respective ideal limit. The magnetic transport scales like beta(2) and is well described by a Rechester-Rosenbluth-type ansatz. (C) 2008 American Institute of Physics. [DOI:10.1063/1.3005380]