Numerical convergence tests for a kinetic closure of fluid moments¹

-R.E. WALTZ and F.D. HALPERN, General Atomics. A method for a kinetic closure of fluid moments for a magnetized plasma with arbitrary collisionality has been developed[1]. The velocity distribution functions are expanded in 8 Gaussian Radial Basis Functions (GRBFs) which are shifted Maxwellians at eight representative 3D-velocity points of drift. The 8 fluid moments (for particle density, 3 particle fluxes, total energy density, and 3 energy fluxes) time advanced in conservative form with external sources determine the 8 GRBF density weighs in 3D real space. The two closure moments (for the stress tensor and the energy weighted stress tensor) are linearly determined from the GRBF weighs. Moments of the nonlinear Coulomb Fokker-Planck collision operator are evaluated from the GRBF weights. Generalization from 8 to a 12, 16, 20... energy weighted moment hierarchy is straightforward. The method is applied to the problem of ion temperature gradient turbulent transport with adiabatic electrons and drift approximated ions.

[1] R.E. Waltz, F.D. Halpern, Zhao Deng, and J. Candy, “Kinetic fluid moments closure for a magnetized plasma with collisions”, to be published