Numerical Simulation of Phase Space Advection in Gyrokinetic Models of Fusion Plasmas

We describe our progress in the development of a fourth-order, finite-volume discretization of a nonlinear, full-f gyrokinetic Vlasov-Poisson system in mapped coordinates. The approach treats the configuration and velocity components of phase space on an equal footing, using a semi-discretization with limited centered fluxes combined with a fourth-order Runge Kutta integration. The algorithm has been implemented in a new code named COGENT, which is built on the Chombo Adaptive Mesh Refinement library being developed by the SciDAC APDEC project. The algorithm and code have been tested on geodesic acoustic mode problems in a standard equilibrium magnetic geometry by comparing damping rates and frequencies with those predicted by theoretical dispersion analyses. Convergence tests are also performed to verify the expected increase in accuracy as the phase space grid was refined.