Bochum 2015 – wissenschaftliches Programm
P 16.8: Poster
Dienstag, 3. März 2015, 16:30–18:30, Foyer Audimax
Vlasov-hybrid simulations of firehose-unstable plasmas — •Patrick Astfalk1, Frank Jenko1,3, Tobias Görler1, and Francesco Califano2 — 1Max-Planck-Institut für Plasmaphysik, Garching, Germany — 2Physics Department, University of Pisa, Pisa, Italy — 3Department of Physics and Astronomy, University of California, Los Angeles, USA
The firehose instability is a kinetic instability which is driven by pressure anisotropies in high-beta space plasmas such as the solar wind. Since the occurence of the firehose is connected to a subsequent reduction of the pressure anisotropy, its instability threshold sets a limit to the observable anisotropies in firehose-unstable space plasmas. We carried out fully kinetic plasma simulations using the semi-Lagrange code VESPA (Mangeney et al. 2002, Valentini et al. 2007) to investigate the firehose instability in 1D3V and 2D3V setups. Starting from a successful benchmark with the PIC-code PEGASUS (Kunz et al., 2014), we revisited the linear and quasilinear theory of the firehose and checked the theoretical predictions for expected growth rates, frequencies and anisotropy reduction. Perhaps the most interesting topic in current research is the nonlinear evolution of firehose-unstable systems. Nonlinear wave-particle interactions lead to a dissipation of the injected magnetic and electric energy and a subsequent heating of the plasma particles. The detailed mechanisms in this regime are still not fully understood. However, they are the key to an explanation of turbulent heating processes in the solar wind, making this an active field of research.