Viscosity and confinement in magnetized plasma

TL;DR

This paper introduces a scalar viscosity approach in magnetized plasma, solving force density equations to reveal the relationship between viscosity and confinement phenomena, including transport barriers and pedestals.

Contribution

It proposes a novel scalar viscosity method and applies it to solve neoclassical force equations, providing insights into plasma confinement and transport phenomena.

Findings

High viscosity solutions are physically valid.

A clear link between viscosity and confinement modes is established.

Gyroviscous effects are negligible compared to collisional viscosity.

Abstract

An alternative to the Braginskii decomposition is proposed, one rooted in treating the viscosity as a scalar quantity in a coordinate-free representation. With appropriate application to the rate-of-shear tensor, one may solve the neoclassical force density equations for its undetermined velocity dependence, as well as the radial and poloidal profiles mentioned in [R. W. Johnson, Phys. Plasmas, under review], using an improved poloidal expansion. The pseudoplastic behavior of magnetized plasma is again obtained, and the high viscosity solution is determined to be physical. A clear relationship between confinement mode and viscosity is observed, indicating a physical origin for transport barriers, pedestals, and other phenomena. The gyroviscous contribution is found to be an effect on the order of one one-thousandth of one percent of the dominant collisional viscosity.