Long term evolution of magnetic turbulence in relativistic collisionless shocks

Philip Chang, Anatoly Spitkovsky, Jonathan Arons

Research output: Contribution to journalArticlepeer-review

1 Scopus citations

Abstract

We study the long term evolution of magnetic fields generated by an initially unmagnetized collisionless relativistic e+e- shock. Our 2D particle-in-cell numerical simulations show that downstream of such a Weibel-mediated shock, particle distributions are approximately isotropic, relativistic Maxwellians, and the magnetic turbulence is highly intermittent spatially, non-propagating, and decaying. Using linear kinetic theory, we find a simple analytic form for these damping rates. Our theory predicts that the overall magnetic energy decays as (ωp t) -q with q ∼ 1, which compares favorably with simulations, but predicts overly rapid damping of short-wavelength modes. The magnetic trapping of particles within the magnetic structures may be the origin of this discrepancy. We conclude that initially unmagnetized relativistic shocks in electron-positron plasmas are unable to form persistent downstream magnetic fields. These results put interesting constraints on synchrotron models for the prompt and afterglow emission from GRBs.

Original languageEnglish (US)
Pages (from-to)1769-1775
Number of pages7
JournalInternational Journal of Modern Physics D
Volume17
Issue number10
DOIs
StatePublished - Sep 2008

All Science Journal Classification (ASJC) codes

  • Mathematical Physics
  • Astronomy and Astrophysics
  • Space and Planetary Science

Keywords

  • Gamma-ray bursts
  • Plasmas
  • Shock waves
  • Turbulence

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