Diffusive shock acceleration in unmodified relativistic, oblique shocks

• Published in: Astroparticle physics 2004-11, Vol.22 (3-4), p.323-338
• Main Authors: Ellison, Donald C., Double, Glen P.
• Format: Article
• Language: English
• Subjects: Acceleration of particles; ISM: cosmic rays; Relativistic shock waves; γ-ray bursts
• ISSN: 0927-6505; 1873-2852
• DOI: 10.1016/j.astropartphys.2004.08.005

We present results from a fully relativistic Monte Carlo simulation of diffusive shock acceleration (DSA) in unmodified shocks. The computer code uses a single algorithmic sequence to smoothly span the range from non-relativistic speeds to fully relativistic shocks of arbitrary obliquity, providing a powerful consistency check. While known results are obtained for non-relativistic and ultra-relativistic parallel shocks, new results are presented for the less explored trans-relativistic regime and for oblique, fully relativistic shocks. We find, for a wide trans-relativistic range extending to shock Lorentz factors >30, that the particle spectrum produced by DSA varies strongly from the canonical f(p)∝p−4.23 spectrum known to result in ultra-relativistic shocks. Trans-relativistic shocks may play an important role in γ-ray bursts and other sources and most relativistic shocks will be highly oblique.