Construction of three-dimensional equilibria of a magnetically confined plasma with closed and nested toroidal magnetic surfaces

TL;DR

This paper develops methods to construct complex three-dimensional plasma equilibria with nested magnetic surfaces, including asymmetric and stochastic regions, advancing understanding of magnetic confinement configurations.

Contribution

It introduces a novel approach to generate 3D plasma equilibria with pressure anisotropy and asymmetric magnetic surfaces using sinusoidal perturbations of axisymmetric models.

Findings

Formation of magnetic islands and stochastic regions in outer plasma areas.

Persistence of well-defined magnetic surfaces in the inner plasma region.

Demonstration that isomagnetic surfaces are neither necessary nor sufficient for nested magnetic surfaces.

Abstract

We construct fully three-dimensional (3D) equilibria with pressure anisotropy and closed, nested toroidal magnetic surfaces that are strongly asymmetric in the toroidal direction by applying a sinusoidal perturbation to the axisymmetric Solov'ev equilibrium. They also have distinct closed and nested current-density surfaces. For certain values of the free parameters involved, the perturbations lead to the formation of magnetic islands and stochastic areas in the outer plasma region, while well-defined magnetic surfaces persist in the inner region. In addition, it is demonstrated that the existence of closed and nested surfaces within the plasma region on which the magnetic field modulus is uniform (isomagnetic surfaces), related to quasisymmetry, is neither necessary nor sufficient for the existence of respective closed and nested magnetic surfaces.