Coordinate-choice independent expression for drift orbit flux and flux-force relation in neoclassical toroidal viscosity theory

TL;DR

This paper develops a coordinate-choice independent expression for drift orbit flux and flux-force relations in neoclassical toroidal viscosity theory, enabling broader and more flexible applications without relying on specific magnetic surface parametrizations.

Contribution

It introduces a generalized, coordinate-independent formula for drift orbit flux and flux-force relations, eliminating the need for straight field line coordinates in numerical computations.

Findings

Derived a surface-averaged drift orbit flux formula in 1/ν regime.

The formula is insensitive to magnetic surface parametrization.

Broadens applicability of flux-force relation in neoclassical toroidal viscosity theory.

Abstract

A coordinate-choice independent expression does not depend how the magnetic surface is parametrized by (\theta,\zeta). Flux-force relation in neoclassical toroidal viscosity(NTV) theory has been generalized in a coordinate-choice independent way. The expression for the surface averaged drift orbit flux in 1/\nu regime is derived without the requirement of straight field line coordinates. The resulted formula is insensitive to how the magnetic surface is parametrized and broadens the cases where flux-force relation can be applied. Construction of straight field line coordinates is avoided when the formula is used for numerical computation.