MAGNETIC FIELD EVOLUTION IN RELATIVISTIC UNMAGNETIZED COLLISIONLESS SHOCKS

TLDR

We study relativistic unmagnetized collisionless shocks with large two‑dimensional pair‑plasma particle‑in‑cell simulations. High‑energy particles accelerated by the shock drive magnetic field growth over ≳10⁴ plasma times, producing progressively stronger, larger‑scale fields that carry ≳1 % of the downstream energy flux, while the particles themselves carry ≳10 %, implying constraints on the magnetization of relativistic astrophysical flows.

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.