First-order Fermi Particle Acceleration at Relativistic Shock Waves with a 'Realistic' Magnetic Field Turbulence Model
First-order Fermi acceleration process at a relativistic shock wave is investigated by means of Monte Carlo simulations involving numerical integration of particle equations of motion in a turbulent magnetic field near the shock. In comparison to earlier studies a few 'realistic' features of the magnetic field structure are included. The upstream field consists of a mean field component inclined at some angle to the shock normal and finite-amplitude perturbations imposed upon it. The perturbations are assumed to be static in the local plasma rest frame. We apply an analytic model for the turbulence with a flat or a Kolmogorov spectrum within a finite (wide) wave vector range. The magnetic field is continuous across the shock -- the downstream field structure is derived from the upstream one from the hydrodynamical shock jump conditions. We present and discuss the obtained particle spectra and angular distributions at mildly relativistic sub- and superluminal shocks. We show that particle spectra diverge from a simple power-law, an exact shape of the spectrum depends on both an amplitude of the magnetic field perturbations and the considered wave power spectrum.