On the Structure of Relativistic Collisionless Shocks in Electron-Ion Plasmas
A. Spitkovsky. The Astrophysical Journal Letters, 673 (1):
L39(2008)
Abstract
Relativistic collisionless shocks in electron-ion plasmas are thought to occur in the afterglow phase of gamma-ray bursts (GRBs) and in other environments where relativistic flows interact with the interstellar medium. A particular regime of shocks in an unmagnetized plasma has generated much interest for GRB applications. In this Letter, we present ab initio particle-in-cell simulations of unmagnetized relativistic electron-ion shocks. Using long-term 2.5-dimensional simulations with ion-electron mass ratios from 16 to 1000, we resolve the shock formation and reach a steady state shock structure beyond the initial transient. We find that even at high ion-electron mass ratios initially unmagnetized shocks can be effectively mediated by the ion Weibel instability with a typical shock thickness of ~20 ion skin depths. Upstream of the shock, the interaction with merging ion current filaments heats the electron component, so that the postshock flow achieves near-equipartition between the ions and electrons, with the electron temperature reaching 50% of the ion temperature. This energy exchange helps to explain the large electron energy fraction inferred from GRB afterglow observations.
%0 Journal Article
%1 Spitkovsky_2008b
%A Spitkovsky, Anatoly
%D 2008
%J The Astrophysical Journal Letters
%K shock
%N 1
%P L39
%T On the Structure of Relativistic Collisionless Shocks in Electron-Ion Plasmas
%U http://stacks.iop.org/1538-4357/673/i=1/a=L39
%V 673
%X Relativistic collisionless shocks in electron-ion plasmas are thought to occur in the afterglow phase of gamma-ray bursts (GRBs) and in other environments where relativistic flows interact with the interstellar medium. A particular regime of shocks in an unmagnetized plasma has generated much interest for GRB applications. In this Letter, we present ab initio particle-in-cell simulations of unmagnetized relativistic electron-ion shocks. Using long-term 2.5-dimensional simulations with ion-electron mass ratios from 16 to 1000, we resolve the shock formation and reach a steady state shock structure beyond the initial transient. We find that even at high ion-electron mass ratios initially unmagnetized shocks can be effectively mediated by the ion Weibel instability with a typical shock thickness of ~20 ion skin depths. Upstream of the shock, the interaction with merging ion current filaments heats the electron component, so that the postshock flow achieves near-equipartition between the ions and electrons, with the electron temperature reaching 50% of the ion temperature. This energy exchange helps to explain the large electron energy fraction inferred from GRB afterglow observations.
@article{Spitkovsky_2008b,
abstract = {Relativistic collisionless shocks in electron-ion plasmas are thought to occur in the afterglow phase of gamma-ray bursts (GRBs) and in other environments where relativistic flows interact with the interstellar medium. A particular regime of shocks in an unmagnetized plasma has generated much interest for GRB applications. In this Letter, we present ab initio particle-in-cell simulations of unmagnetized relativistic electron-ion shocks. Using long-term 2.5-dimensional simulations with ion-electron mass ratios from 16 to 1000, we resolve the shock formation and reach a steady state shock structure beyond the initial transient. We find that even at high ion-electron mass ratios initially unmagnetized shocks can be effectively mediated by the ion Weibel instability with a typical shock thickness of ~20 ion skin depths. Upstream of the shock, the interaction with merging ion current filaments heats the electron component, so that the postshock flow achieves near-equipartition between the ions and electrons, with the electron temperature reaching 50% of the ion temperature. This energy exchange helps to explain the large electron energy fraction inferred from GRB afterglow observations.},
added-at = {2012-04-11T14:04:10.000+0200},
author = {Spitkovsky, Anatoly},
biburl = {https://www.bibsonomy.org/bibtex/213a4e80e5545ee8972759bd26dc99fe0/pkilian},
interhash = {ed987514b44e22c7f74b27045abd6806},
intrahash = {13a4e80e5545ee8972759bd26dc99fe0},
journal = {The Astrophysical Journal Letters},
keywords = {shock},
number = 1,
pages = {L39},
timestamp = {2012-04-11T14:07:31.000+0200},
title = {On the Structure of Relativistic Collisionless Shocks in Electron-Ion Plasmas},
url = {http://stacks.iop.org/1538-4357/673/i=1/a=L39},
volume = 673,
year = 2008
}