Unified plasma fluid/kinetic equations for tokamak microinstability and turbulence studies

Unified fluid/kinetic equations for the plasma perturbed density (n), parallel flow velocity (uparallel) and temperature (T) are developed by calculating the fluid moment closure relations kinetically. To calculate closure relations for b·∇·Πparallel and ∇·q to be used in a set of perturbed fluid equations for n, uparallel and T, a linearized drift-kinetic Chapman-Enskog-type equation is solved in a sheared slab geometry. A moment approach and a physically realistic collision operator (Lorentz scattering operator plus the momentum restoring terms) are used. The resultant closure relations for πparallel and qparallel possess both the fluid and kinetic properties. In the fluid collisional limit the equations reduce to the well-known Braginskii equations. In the adiabatic limit they reproduce the usual kinetic results, including Landau damping. It is shown that the Chapman-Enskog-type approach is more compatible with a fluidlike description of plasmas than the usual gyrokinetic approach. The unified fluid/kinetic equation set is valid for arbitrary values of ν/ω (collisionality) and ω/kparallelvt (strength of Landau damping). Applications of this set of equations show that many well-known microinstabilities (collisionless and dissipative electron drift instabilities, ηi modes, micro-tearing modes, etc.) are covered by these equations when appropriate limits are taken. Generalized nonlocal eigenvalue equations for electron and ion drift type modes and micro-tearing type modes are presented. The feasibility of including magnetic trapped particle effects in the fluid equations through the closure equations and thus the derivation of trapped-particle instabilities by this procedure, is also demonstrated. 4 refs