Tuesday

The current filamentation instability (CFI) is a kinetic instability capable of generating an intense magnetic field in initially unmagnetised plasmas. The instability is thought to mediate the formation of collisionless shocks in many astrophysical environments, from supernova remnants to gamma-ray bursts [1].

In this work, we investigate the onset and development of the CFI in counterstreaming non-relativistic unmagnetized ion-electron flows for different plasma parameters. Taking full advantage of the semi-implicit algorithm implemented in the energy-conserving Particle-In-Cell code ECsim [2], we examine the long-term evolution of the instability on ion time-scales. Our numerical results indicate that the magnetic field generated by the instability survives for hundreds of ion plasma periods. During the non-linear phase of the instability, the magnetic field evolves from short spatial scales towards large spatial scales. This process seems to be continually supported by the ion anisotropy that drives the CFI. While the anisotropy shows an abrupt drop during the linear phase of the instability, it continues decreasing with time as t^(-β) with β= 0.01 - 0.5 and remains substantially large at the end of our simulations.

[1] M. V. Medvedev at al., Astrophys. J. 526, 697 (1999). M. V. Medvedev et al., Astrophys. J. Lett. 618, L75 (2005). Ardaned et al., Astrophys.
J. 11, 57 (2011). K. I. Nishikawa et al., Astrophys. J. 595, 555 (2003).
[2] G. Lapenta et al., J. Plasma Phys. 83, 705830205 (2017).