Prescriptions for electron injection into the diffusive shock acceleration process are required
in many practical considerations of cosmic-ray astrophysics, particularly in modeling of the
synchrotron emission of astrophysical sources. In particle-in-cell simulations of quasi-
parallel magnetized collisionless shocks, we analyse the evolution of particle spectra. We
find that in the later stages of shock evolution, the initially strong suprathermal part in the ion
spectra fades, thus leaving the spectra composed of a Maxwellian and a power law. Once …