Radially local approximation of the drift kinetic equation

TL;DR

This paper introduces a new radially local drift kinetic equation that improves numerical simulation properties and satisfies key physical conditions like ambipolarity and Onsager symmetry in neoclassical transport.

Contribution

The paper presents a novel radially local drift kinetic equation including magnetic drifts, with improved numerical and physical properties, and derives a second form emphasizing entropy and symmetry.

Findings

The new equation includes both ${f E} imes {f B}$ and magnetic drifts.

It satisfies the ambipolarity condition under quasisymmetry.

A second form ensures positive entropy production and Onsager symmetry.

Abstract

A novel radially local approximation of the drift kinetic equation is presented. The new drift kinetic equation that includes both ${\bf E} \times {\bf B}$ and tangential magnetic drift terms is written in the conservative form and it has favorable properties for numerical simulation that any additional terms for particle and energy sources are unnecessary for obtaining stationary solutions under the radially local approximation. These solutions satisfy the intrinsic ambipolarity condition for neoclassical particle fluxes in the presence of quasisymmetry of the magnetic field strength. Also, another radially local drift kinetic equation is presented, from which the positive definiteness of entropy production due to neoclassical transport and Onsager symmetry of neoclassical transport coefficients are derived while it sacrifices the ambipolarity condition for neoclassical particle fluxes in axisymmetric and quasi-symmetric systems.