A Generalized Hasegawa-Mima Equation in Curved Magnetic Fields

TL;DR

This paper derives a generalized Hasegawa-Mima equation to model electrostatic plasma turbulence in curved magnetic fields, extending previous models to more complex geometries relevant for plasma confinement devices.

Contribution

The paper introduces a new nonlinear equation that accounts for magnetic field curvature effects on plasma turbulence, broadening the applicability of drift wave models.

Findings

The derived equation conserves energy and, under certain conditions, enstrophy.

Magnetic field curvature influences the structure of steady turbulent states.

Numerical simulations demonstrate the impact of curvature on turbulence patterns.

Abstract

We derive a model equation describing electrostatic plasma turbulence in general (inhomogeneous and curved) magnetic fields by analysing the effect of curved geometry on the ion fluid polarization drift velocity. The derived nonlinear equation generalizes the Hasegawa-Mima equation governing drift wave turbulence in a straight homogeneous magnetic field, and may serve as a toy model for the description of turbulent systems such as the core of H-mode plasmas. The equation is most appropriate for configurations with a small ExB drift velocity divergence, or a mild spatial change in ExB drift velocity. We identify the conserved energy of the system, and obtain conditions on magnetic field topology for conservation of generalized enstrophy. Through numerical examples, we further show how the curvature of the magnetic field reshapes self-organized steady turbulent states.