2019/07/25 by M. Lemoine, Martin Lemoine, Arno Vanthieghem +5
Physics and Astronomy · #Astrophysics and Cosmic Phenomena #Atomic physics #Classical mechanics #Filamentation #Gamma-ray bursts and supernovae #Lorentz factor #Lorentz transformation #Microturbulence #Physics #Plasma #Pulsars and Gravitational Waves Research #Quantum mechanics #Shock (circulatory) #Virial theorem #astro-ph.HE #physics.plasm-ph
paper · pdf · doi:10.1103/physreve.100.033209
published as Phys. Rev. E 100, 033209 (2019) · Phys. Rev. E, submitted; 17 pages, 7 figures
arxiv created 2019/07/25 · openalex publication_date 2019/09/24 · arxiv updated 2019/10/02 · openalex created_date 2025/10/10 · openalex updated_date 2026/08/05
In this second paper of a series, we discuss the dynamics of a plasma entering the precursor of an unmagnetized, relativistic collisionless pair shock. We discuss how this background plasma is decelerated and heated through its interaction with a microturbulence that results from the growth of a current filamentation instability in the shock precursor. We make use, in particular, of the reference frame Rw in which the turbulence is mostly magnetic. This frame moves at relativistic velocities towards the shock front at rest, decelerating gradually from the far to the near precursor. In a first part, we construct a fluid model to derive the deceleration law of the background plasma expected from the scattering of suprathermal particles off the microturbulence. This law leads to the relationship γp∼ξb-1/2 between the background plasma Lorentz factor γp and the normalized pressure of the beam ξb; it is found to match nicely the spatial profiles observed in large-scale 2D3V particle-in-cell simulations. In a second part, we model the dynamics of the background plasma at the kinetic level, incorporating the inertial effects associated with the deceleration of Rw into a Vlasov-Fokker-Planck equation for pitch-angle diffusion. We show how the effective gravity in Rw drives the background plasma particles through friction on the microturbulence, leading to efficient plasma heating. Finally, we compare a Monte Carlo simulation of our model with dedicated PIC simulations and conclude that it can satisfactorily reproduce both the heating and the deceleration of the background plasma in the shock precursor, thereby providing a successful one-dimensional description of the shock transition at the microscopic level.