Topic/Type: 2.3 Hybrid methods, including PIC/DSMC and PIC/Fluid, Poster

dHybrid: a 3D kinetic ion fluid electron code for space and astrophysical plasma simulations

L. Gargat?1, R. A. Fonseca1, 2, R. Bingham3, L. O. Silva1

1 IPFN, Instituto Superior T?cnico, Lisboa, Portugal
2 2DCTI, Instituto Superior de Ci?ncias do Trabalho e da Empresa, Lisboa, Portugal
3 SSTD, Science & Technology Facilities Council, Rutherford Appleton Laboratory, Didcot, UK

The hybrid model implemented in dHybrid, a three-dimensional massively parallel code, assumes the electrons are massless, and neglects the displacement current in Amp?re?s law. High-frequency oscillations due to the electrons are neglected, and only the kinetics of the ions is retained, allowing for longer simulation times than in fully kinetic simulations, and allowing for more realistic plasma parameters to be simulated.

Here, we show the main characteristics of dHybrid, including the parallelization techniques employed, and integration of the code with the diagnostics and visualization routines. We present the state-of-the-art algorithms employed in particle tracking, which are a key element in the study of particle acceleration in astrophysical shocks. We further highlight the applicability of the code to astrophysical scenarios by studying the amplification of the seed magnetic field in Supernova Remnant (SNR) Shocks, relevant for the acceleration of Cosmic Ray (CR) particles.

The saturation mechanism of the non-resonant Bell instability [1] is explored in different regimes when: i) the driving current is externally imposed and independent of the magnetic field growth (external driver), and ii) the driving current is modeled as a particle flow in the simulation, thus allowing feedback of magnetic turbulence on the CR trajectories (kinetic driver). Our results show a significant magnetic field enhancement B >> B0 in both cases, as expected from theory. The non-linear growth phase and the saturation phase are explored in detail, leveraging on the unique characteristics of hybrid codes, including the reaction of the background plasma and the CR plasma. A thorough discussion of the relevance of the mechanism to the CR acceleration at SNR shocks is also presented.

[1] A. R. Bell, Mon. Not. R. Astron. Soc. 353, 550, 2004