Three-Dimensional Particle-In-Cell Simulations of Two-Dimensional Bernstein-Greene-Kruskal Modes

TL;DR

This study uses 3D Particle-In-Cell simulations to examine the stability of 2D BGK modes in magnetized plasma, confirming previous 2D results and exploring effects of density variations and thermal velocities.

Contribution

First 3D PIC simulation study confirming 2D BGK mode stability results and analyzing effects of density structures and thermal velocities.

Findings

2D stability results hold in 3D simulations

Instability develops slower in 3D with spiral wave structures

Density variations influence spiral wave structures

Abstract

In this paper, we present three-dimensional (3D) Particle-In-Cell (PIC) simulations to study the stability of 2D Bernstein-Greene-Kruskal (BGK) modes in a magnetized plasma with a finite background magnetic field. The simulations were performed using the Plasma Simulation Code (PSC) [Germaschewski et al., J. of Comp. Phys. 318, 305 (2016)], as in our recent study using 2D PIC simulations [McClung et al., Phys. Plasmas 31, 042302 (2024)], in order to see if and how the previous results would change with 3D effects. We found that solutions that are stable (unstable) in 2D simulations are still stable (unstable) in the new 3D simulations. However, the instability develops slower in 3D than in 2D and forms an unstable spiral wave structure that is in-phase along the axial direction. We have also simulated cases with an electron density bump (EDB) at the center, in addition to cases with an electron density hole (EDH) considered in our previous study, and found differences in the unstable spiral wave structures between the two cases. Additionally, we have generalized our simulations to have an increased electron thermal velocity, as well as using initial conditions solved from the complete Vlasov-Maxwell system of equations. We found that these generalizations did not change the overall behavior of the simulations and the instability that evolves.