The Gyrokinetic Description of Microturbulence in Magnetized Plasmas

Nonlinear gyrokinetics is the major formalism used for both the analytical and numerical descriptions of low-frequency microturbulence in magnetized plasmas. Its derivation from noncanonical Lagrangian methods and field-theoretic variational principles is summarized. Basic properties of gyrokinetic physics are discussed, including polarization and the concept of the gyrokinetic vacuum, equilibrium statistical mechanics, and the two fundamental constituents of gyrokinetic turbulence, namely drift waves and zonal flows. Numerical techniques are described briefly, and illustrative simulation results are presented. Advanced topics include the transition to turbulence, the nonlinear saturation of turbulence by coupling to damped gyrokinetic eigenmodes, phase-space cascades, subcritical turbulence, and momentum conservation.