Non-physical momentum sources in slab geometry gyrokinetics
PLASMA PHYSICS AND CONTROLLED FUSION 52:8 (2010) ARTN 085011
Turbulent transport of toroidal angular momentum in low flow gyrokinetics (vol 52, 045004, 2010)
PLASMA PHYSICS AND CONTROLLED FUSION 52:5 (2010) ARTN 059801
Comment on On higher order corrections to gyrokinetic Vlasov-Poisson equations in the long wavelength limit [Phys. Plasmas 16, 044506 (2009)]
Physics of Plasmas 16:12 (2009)
Abstract:
A recent publication [F. I. Parra and P. J. Catto, Plasma Phys. Controlled Fusion 50, 065014 (2008)] warned against the use of the lower order gyrokinetic Poisson equation at long wavelengths because the long wavelength, radial electric field must remain undetermined to the order the equation is obtained. Another reference [W. W. Lee and R. A. Kolesnikov, Phys. Plasmas 16, 044506 (2009)] criticizes these results by arguing that the higher order terms neglected in the most common gyrokinetic Poisson equation are formally smaller than the terms that are retained. This argument is flawed and ignores that the lower order terms, although formally larger, must cancel without determining the long wavelength, radial electric field. The reason for this cancellation is discussed. In addition, the origin of a nonlinear term present in the gyrokinetic Poisson equation [F. I. Parra and P. J. Catto, Plasma Phys. Controlled Fusion 50, 065014 (2008)] is explained. © 2009 American Institute of Physics.Vorticity and intrinsic ambipolarity in turbulent tokamaks
Plasma Physics and Controlled Fusion 51:9 (2009)
Abstract:
Traditional electrostatic gyrokinetic treatments consist of a gyrokinetic Fokker-Planck equation and a gyrokinetic quasineutrality equation. Both of these equations can be found up to second order in a gyroradius over macroscopic length expansion in some simplified cases, but the versions implemented in codes are typically only first order. In axisymmetric configurations such as the tokamak, the accuracy to which the distribution function is calculated is insufficient to determine the neoclassical radial electric field. Moreover, we prove here that turbulence dominated tokamaks are intrinsically ambipolar, as are neoclassical tokamaks. Therefore, traditional gyrokinetic descriptions are unable to correctly calculate the toroidal rotation and hence the axisymmetric radial electric field. We study the vorticity equation, ∇ J = 0, in the gyrokinetic regime, with wavelengths on the order of the ion Larmor radius. We explicitly show that gyrokinetics needs to be calculated at least to third order in the gyroradius expansion if the radial electric field is to be retrieved from quasineutrality. The method employed to study the vorticity equation also suggests a solution to the problem, namely, solving a gyrokinetic vorticity equation instead of the quasineutrality equation. The vorticity equations derived here only obtain the potential within a flux function as required. © 2009 IOP Publishing Ltd.Limitations, insights and improvements to gyrokinetics
Nuclear Fusion 49:9 (2009)