Magnetic field evolution in relativistic unmagnetized collisionless shocks

Abstract

We study relativistic unmagnetized collisionless shocks using unprecedentedly large particle-in-cell simulations of two-dimensional pair plasma. High-energy particles accelerated by the shock are found to drive magnetic field evolution on a timescale ≳104 plasma times. Progressively stronger magnetic fields are generated on larger scales in a growing region around the shock. Shock-generated magnetic fields and accelerated particles carry ≳1% and ≳10% of the downstream energy flux, respectively. Our results suggest limits on the magnetization of relativistic astrophysical flows. © 2009. The American Astronomical Society. All rights reserved..