Symmetries of a reduced fluid-gyrokinetic system

TL;DR

This paper investigates the symmetries of a fully gyrokinetic fluid-gyrokinetic model using Lie group techniques, uncovering new exact symmetries and constructing novel nonlinear solutions like a helical collapsing current sheet.

Contribution

It identifies a wide range of symmetries in a complex gyrokinetic model and derives new nonlinear solutions, including a helical generalization of the Chapman-Kendall solution.

Findings

Uncovered a variety of exact symmetries, some with unexpected forms.

Constructed new nonlinear solutions, including a helical collapsing current sheet.

Extended understanding of symmetry properties in gyrokinetic plasma models.

Abstract

Symmetries of a fluid-gyrokinetic model are investigated using Lie group techniques. Specifically the nonlinear system constructed by Zocco and Schekochihin (Zocco & Schekochihin 2011), which combines nonlinear fluid equations with a drift-kinetic description of parallel electron dynamics, is studied. Significantly, this model is fully gyrokinetic, allowing for arbitrary k_perp rho_i , where k_perp is the perpendicular wave vector of the fluctuations and rho_i the ion gyroradius. The model includes integral operators corresponding to gyroaveraging as well as the moment equations relating fluid variables to the kinetic distribution function. A large variety of exact symmetries is uncovered, some of which have unexpected form. Using these results, new nonlinear solutions are constructed, including a helical generalization of the Chapman-Kendall solution for a collapsing current sheet.