Kinetic simulations of the filamentation instability in pair plasmas

The non-linear interaction between electromagnetic waves and plasmas attracts significant attention in astrophysics because it can affect the propagation of Fast Radio Bursts (FRBs) - luminous millisecond-duration pulses detected at radio frequency. The filamentation instability (FI) - a type of non-linear wave-plasma interaction - is considered to be dominant near FRB sources, and its non-linear development may also affect the inferred dispersion measure of FRBs. In this paper, we carry out fully kinetic particle-in-cell simulations of the FI in unmagnetized pair plasmas. Our simulations show that the FI generates transverse density filaments, and that the electromagnetic wave propagates in near vacuum between them, as in a waveguide. The density filaments keep merging until force balance between the wave ponderomotive force and the plasma pressure gradient is established. We estimate the merging time-scale and discuss the implications of filament merging for FRB observations.

Automated summary

In this paper, the filamentation instability (FI) in unmagnetized pair plasmas is studied using fully kinetic particle-in-cell simulations. The results show that the FI generates transverse density filaments, and the electromagnetic wave propagates in near vacuum between them, resembling a waveguide. The density filaments continue to merge until force balance is established between the wave ponderomotive force and the plasma pressure gradient. The merging time-scale is estimated and the implications for FRB observations are discussed.