Nonlinear finite-Larmor-radius effects in reduced fluid models

The polarization magnetization effects associated with the dynamical reduction leading to the nonlinear gyrokinetic Vlasov-Maxwell equations are shown to introduce nonlinear finite-Larmor-radius (FLR) effects into a set of nonlinear reduced-fluid equations previously derived by the Lagrangian variational method [A. J. Brizard, Phys. Plasmas 12, 092302 (2005)]. These intrinsically nonlinear FLR effects, which are associated with the transformation from guiding-center phase-space dynamics to gyrocenter phase-space dynamics, are different from the standard FLR corrections associated with the transformation from particle to guiding-center phase-space dynamics. We also present the linear dispersion relation results from a nonlinear simulation code using these reduced-fluid equations. The simulation results (in both straight dipole geometries) demonstrate that the equations describe the coupled dynamics of Alfven sound waves and that the total simulation energy is conserved. (C) 2008 American Institute of Physics.