One dimensional PIC simulation of relativistic Buneman instability

Abstract

Spatio-temporal evolution of the relativistic Buneman instability has been investigated in one dimension using an in-house developed particle-in-cell simulation code. Starting from the excitation of the instability, its evolution has been followed numerically till its quenching and beyond. As compared to the well understood non-relativistic case, it is found that the maximum growth rate ($\gamma_{max}$) reduces due to relativistic effects and varies with $\gamma_{e0}$ and m/M as $\gamma_{max} \sim \frac{\sqrt{3}}{2\sqrt{\gamma_{e0}}}\biglb(\frac{m}{2M}\bigrb)^{1/3}$, where $\gamma_{e0}$ is Lorentz factor associated with the initial electron drift velocity ($v_{0}$) and (m/M) is the electron to ion mass ratio. Further it is observed that in contrast to the non-relativistic results[Hirose,Plasma Phys. 20, 481(1978)] at the saturation point, ratio of electrostatic field energy density ($\sum\limits_{k} |E_{k}|^{2}/8\pi$) to initial drift kinetic energy density ($W_{0}$) scales with $\gamma_{e0}$ as $\sim 1/\gamma^{2}_{e0}$. These simulation results are found to be in good agreement with that derived using fluid theory.