Kinetic Flux Ropes: Bernstein-Greene-Kruskal Modes for the Vlasov-Poisson-Amp\`{e}re System

TL;DR

This paper extends the theoretical framework of BGK modes in collisionless plasmas to include azimuthal magnetic fields, providing exact solutions to the Vlasov-Poisson-Ampère system that describe electrostatic structures with current-carrying magnetic fields.

Contribution

It generalizes previous BGK mode solutions to cases with azimuthal magnetic fields, satisfying the full Vlasov-Poisson-Ampère system.

Findings

Exact solutions for current-carrying electrostatic structures

Explicit examples with positive and negative potentials

Extension of BGK modes to magnetized plasmas with azimuthal fields

Abstract

Electrostatic structures have been observed in many regions of space plasmas, including the solar wind, the magnetosphere, the auroral acceleration region. One possible theoretical description of some of these structures is the concept of Bernstein-Greene-Kruskal (BGK) modes, which are exact nonlinear steady-state solutions of the Vlasov-Poisson system of equations in collisionless kinetic theory. We generalize exact solutions of two-dimensional BGK modes in a magnetized plasma with finite magnetic field strength [Ng, Bhattacharjee, and Skiff, Phys. Plasmas {\bf13}, 055903 (2006)] to cases with azimuthal magnetic fields so that these structures carry electric current as well as steady electric and magnetic fields. Such nonlinear solutions now satisfy exactly the Vlasov-Poisson-Amp\`{e}re system of equations. Explicit examples with either positive or negative electric potential structure are provided.