Speaker
Illya Plotnikov
Description
See the full Abstract at http://ocs.ciemat.es/EPS2018ABS/pdf/P5.4014.pdf
Perpendicular relativistic shocks in magnetized pair plasmas
I. Plotnikov1,2, A. Grassi3,4,5, M. Grech3
1
Institut de Recherche en Astrophysique et Planétologie, Toulouse, France
2
Department of Astrophysical Sciences, Princeton, USA
3
Laboratoire d'Utilisation des Lasers Intenses, Paris, France
4
Dipartimento di Fisica Enrico Fermi, Pisa, Italy
5
Istituto Nazionale di Ottica, Pisa, Italy
Perpendicular relativistic shocks in magnetized pair plasmas [1] are investigated using
two-dimensional Particle-In-Cell (PIC) simulations. In a first part of this work, a systematic
survey, from unmagnetized to strongly magnetized plasmas (upstream flow magnetizations
from σ = 10-6 to 10), is presented for an initial flow Lorentz factor γ0 = 10. The mechanisms
behind shock formation (from Weibel-mediated to magnetic-reflection), the global structure
of the shock, and comparison to MHD predictions are discussed for the whole range of
upstream magnetizations. The characteristic time of shock formation is also investigated
focusing on both density compression and isotropization of the downstream plasma.
The second part of this work focuses on particle acceleration in the shock. It is found to be
efficient at weak to intermediate magnetizations and fully suppressed for σ >10-2. The
relative importance of diffusive shock acceleration and shock drift acceleration will be
discussed, the spatial diffusion coefficients extracted from the simulations presented. A
scaling of the accelerated particle maximum energy with the upstream flow magnetization
γmax ∝ σ-1/2
for 10-3< σ <10-2 will be presented and the difference with that obtained by
Sironi et al. [2] at lower magnetization will be discussed.
[1] Plotnikov, Grassi and Grech, arXiv:1712.02883.
[2] Sironi, Spitkovsky and Arons, ApJ 771, 54 (2013).
