Polarization and magnetization in collisional and turbulent transport processes

TL;DR

This paper derives comprehensive expressions for polarization and magnetization in magnetically confined plasmas, incorporating full gyroradius expansions and turbulence effects, to improve gyrokinetic simulations of plasma transport.

Contribution

It introduces new gyrokinetic equations including turbulence and polarization effects, enhancing the accuracy of electromagnetic plasma transport modeling.

Findings

Derived full-expansion polarization and magnetization expressions.

Confirmed turbulent gyrokinetic equations align with WKB results.

Identified importance of second-order terms for high-beta plasma simulations.

Abstract

Expressions of polarization and magnetization in magnetically confined plasmas are derived, which include full expansions in the gyroradius to treat effects of both equilibrium and microscopic electromagnetic turbulence. Using the obtained expressions, densities and flows of particles are related to those of gyrocenters. To the first order in the normalized gyroradius expansion, the mean part of the particle flow is given by the sum of the gyrocenter flow and the magnetization flow, which corresponds to the so-called magnetization law in drift kinetics, while the turbulent part contains the polarization flow as well. Collisions make an additional contribution to the second-order particle flow. The mean particle flux across the magnetic surface is of the second-order and it contains classical, neoclassical, and turbulent transport processes. The Lagrangian variational principle is used to derive the gyrokinetic Poisson and Amp\`{e}re equations which properly include mean and turbulent parts so as to be useful for full-$f$ global electromagnetic gyrokinetic simulations. It is found that the second-order Lagrangian term given by the inner product of the turbulent vector potential and the drift velocity consisting of the curvature drift and the $\nabla B$ drift should be retained in order for the derived Amp\`{e}re equation to correctly include the diamagnetic current which is necessary especially for the full-$f$ high-beta plasma simulations. The turbulent parts of these gyrokinetic Poisson and Amp\`{e}re equations are confirmed to agree with the results derived from the WKB representation in earlier works.