The understanding of the particle spectra resulting from acceleration in relativistic shocks as they occur in extragalactic sources is essential for the interpretation of the Cosmic Ray spectrum above the ankle (E>3*1e18 eV). It is believed that extragalactic sources like Active Galactic Nuclei and Gamma Ray Bursts can produce particle spectra up to E~1e21 eV. In this contribution, subluminal shocks are investigated with respect to different shock boost factors Gamma and the inclination angle between the shock normal and the magnetic field psi. A correlation between the boost factor and the spectral behavior of the emitted particles is found. The results are compared to Gamma Ray Burst observations and the Cosmic Ray spectrum at the highest energies.

Proceedings of the 30th International Cosmic Ray Conference; Rogelio Caballero, Juan Carlos D'Olivo, Gustavo Medina-Tanco, Lukas Nellen, Federico A. Sánchez, José F. Valdés-Galicia (eds.); Universidad Nacional Autónoma de México, Mexico City, Mexico, 2008; Vol. 2 (OG part 1), pages 287-290