Three-dimensional dynamics of relativistic flows in pair plasmas with force-free magnetic configuration

Abstract

Dynamics of the relativistic flow in pair plasmas with force-free magnetic configuration is investigated by using a three-dimensional fully relativistic electromagnetic particle-in-cell code. This study is an extension of the work by Haruki and Sakai [Phys. Plasmas 8, 1538 (2001)] that was done in a two-dimensional force-free magnetic configuration. They found that during the early stage of the interaction there occurs the streaming instability, which induces the electromagnetic perturbations associated with generation of quasi-static magnetic field. In the nonlinear stage the force-free magnetic field becomes unstable against the firehose instability and then magnetic islands are formed through magnetic reconnection. The dissipated magnetic field energy is converted to the plasma heating as well as the high-energy particle production. It is found that the three-dimensional configuration could result in completely different dynamics, except for the initial phase where the streaming instability develops. It is also found that the dynamical interaction between the force-free magnetic configuration and the relativistic plasma flows develops sequentially through four different physical processes: (I) The phase of streaming instability, (II) the phase of magnetic reconnection triggered by the first streaming instability, (III) the phase of Alfvén wave excitation through the magnetic reconnection process, and (IV) the phase of dissipation of the Alfvén waves through the magnetic reconnection. It is shown that three-dimensional Alfvén waves with helical magnetic structures can be excited through complicated three-dimensional tearing instability triggered from the streaming instability. During these dynamical processes the pair plasma can be heated through the magnetic reconnection and also the high-energy particles are generated. The interaction process between the force-free collisionless plasmas and the relativistic plasma flows may play an important role for the effective magnetic field energy dissipation, formation of filament structures, and high-energy particle production in astrophysical plasmas.