A comparative study of current and magnetic structures of Weibel and filamentation instabilities

A comparative study of the Weibel instability (WI) driven by anisotropic temperature and the Filamentation instability (FI) by counterstreaming plasmas are made by using a 2D Particle-in-cell code. Under the comparable initial conditions, the linear growth rates of the WI and the FI are almost the same as the theory predicts, but in the nonlinear phase, the maximum and nonlinearly saturated magnetic fields generated by the WI are always smaller than those generated by the FI. It is noted that in the initial linear growth phase, the WI and the FI both have center-filled currents, but in the nonlinear phase, the WI and the FI develop different types of current structures such that the WI maintains a center-filled current structure, whereas the FI develops a hollow current structure. Significant particle acceleration around the drift velocity is observed for the FI, whereas it is almost absent in the WI, which indicates that the enhanced velocity of the electron by particle acceleration is related to the hollow current production in the FI. (C) 2014 AIP Publishing LLC.