On the gyrokinetic equilibrium

Qin, H.; Tang, W. M.; Rewoldt, G.; Lee, W. W.

doi:doi:10.1063/1.873898

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Nondissipative kinetic simulation and analytical solution of three-mode equations of the ion temperature gradient instability

A nondissipative drift kinetic simulation scheme, which rigorously satisfies the time-reversibility, is applied to the three-mode coupling problem of the ion temperature gradient (ITG) instability. It is found from the simulation that the three-mode ITG system repeats growth and decay with a period which shows a logarithmic divergence for infinitesimal initial perturbations. Accordingly, time average of the mode amplitude vanishes, as the initial amplitude approaches zero. An exact solution is a...

Self-consistent distributions in collisional absorption of intense laser fields

The influence of the shape of the electron velocity distribution on collisional absorption of laser irradiation in a plasma is considered, describing its self-consistent evolution by a Boltzmann equation, and treating collisions with (immobile) ions and among electrons in Fokker–Planck approximation. In order to facilitate numerical solutions for intensities where the distribution is displaced by several times its width it is approximated as isotropic in a reference frame moving with the average...

Recent developments in gyrokinetic-magnetohydrodynamics (MHD) theory and in electromagnetic gyrokinetic particle simulations raise the question of consistency between the gyrokinetic model and the fluid model. Due to the special characteristics of the guiding center coordinates, it is a nontrivial exercise to show this consistency. In this paper it is shown, in a very general setting, that the gyrokinetic theory and the fluid equations do give an equivalent description of plasma equilibrium (∂/∂t = 0). The fluid continuity equation and momentum equation for equilibrium plasmas are recovered entirely from the gyrokinetic theory. However, it was Spitzer who first realized the importance of consistency between guiding-center motion and fluid equations. In particular, he studied the “apparent paradoxical result” regarding the difference between perpendicular particle flow and guiding-center flow, which will be referred to as the Spitzer paradox in this paper. By recovering the fluid equations from the gyrokinetic theory, we automatically resolve the Spitzer paradox, whose essence is how the perpendicular current and flow are microscopically generated from particles’ guiding-center motion. The mathematical construction in the gyrokinetic theory which relates observable quantities in the laboratory frame to the distribution function in the guiding-center coordinates is consistent with Spitzer’s original physical picture, while today’s gyrokinetic-MHD theory covers a much wider range of problems in a much more general and quantitative way. © 2000 American Institute of Physics.

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KEYWORDS and PACS

Keywords

plasma magnetohydrodynamics, PLASMA SIMULATION, MHD EQUILIBRIUM, GYROMAGNETIC RATIO, PLASMA FLUID EQUATIONS, MAGNETOHYDRODYNAMICS, MOTION, DYNAMICS, ORBITS, TRAJECTORIES

PACS

52.25.Fi

Transport properties
52.25.Dg

Plasma kinetic equations
52.35.Py

Macroinstabilities (hydromagnetic, e.g., kink, fire-hose, mirror, ballooning, tearing, trapped-particle, flute, Rayleigh-Taylor, etc.)