Three-dimensional particle-in-cell simulations of two-dimensional Bernstein–Greene–Kruskal modes

In this paper, we present three-dimensional (3D) particle-in-cell (PIC) simulations to study the stability of 2D Bernstein–Greene–Kruskal modes in a magnetized plasma with a finite background magnetic field. The simulations were performed using the Plasma Simulation Code [Germaschewski et al., J. Comput. 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 at the center, in addition to cases with an electron density hole 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.