MAGNETIC FIELD EVOLUTION IN RELATIVISTIC UNMAGNETIZED COLLISIONLESS SHOCKS

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 greater than or similar to 10(4) 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 greater than or similar to 1% and greater than or similar to 10% of the downstream energy flux, respectively. Our results suggest limits on the magnetization of relativistic astrophysical flows.