Investigation of the ion Weibel instability: kinetic simulations in support of a laser-driven experiment on OMEGA

In astrophysical plasmas, high magnetic fields are commonplace but their origins and the amplification processes responsible for generating them are not entirely understood. One candidate for the amplification of seed magnetic fields is the ion Weibel instability. Counter-streaming plasma flows in the presence of seed fields form current filaments causing the initial magnetic field to grow. The nonlinear dynamics of current filaments are not understood, especially at late times, and theoretical predictions differ depending on what physics is included. Previous experiments have demonstrated the development of Weibel-generated current filaments from interpenetrating ion flows but have not recorded data at late enough times to differentiate between models. New experiments have been performed at OMEGA to observe the nonlinear dynamics of current filaments at later times (t >10ns). Relevance of the data to theoretical models depends on our understanding of the magnetic field topology and experimental plasma conditions including ion-ion collisionality and resistivity. In this work we present a fully kinetic particle-in-cell simulation, with conditions matched to the latest experiments, to model the linear growth and subsequent nonlinear evolution of the Weibel instability. Simulation results are interpreted with reference to spatially resolved Thomson scattering measurements and proton radiographs.

This work was supported by the U.S. DOE NNSA, NLUF and LLNL under Contract DE-AC52-07NA27344.