Consistency in Drift-ordered Fluid Equations

TL;DR

This paper derives consistent drift-ordered fluid equations from a Galilean invariant system, analyzes their quasi-neutral limit, and validates the approach through numerical simulations across different plasma regimes.

Contribution

It provides a systematic derivation of drift-fluid equations ensuring consistency and conservation, including first-order corrections and their numerical validation.

Findings

First-order corrections improve accuracy in plasma modeling.

The equations preserve constants of motion at each order.

Numerical simulations confirm validity across various plasma conditions.

Abstract

We address several concerns related to the derivation of drift-ordered fluid equations. Starting from a fully Galilean invariant fluid system, we show how consistent sets of perturbative drift-fluid equations in the case of a isothermal collisionless fluid can be obtained. Treating all the dynamical fields on equal footing in the singular-drift expansion, we show under what conditions a set of perturbative equations can have a non-trivial quasi-neutral limit. We give a suitable perturbative setup where we provide the full set of perturbative equations for obtaining the first-order corrected fields and show that all the constants of motion are preserved at each order. With the dynamical field variables under perturbative control, we subsequently provide a quantitative analysis by means of numerical simulations. With direct access to first-order corrections the convergence properties are addressed for different regimes of parameter space and the validity of the first-order approximation is discussed in the three settings: cold ions, hot ions and finite charge density.