Time‐dependent Numerical Model for the Emission of Radiation from Relativistic Plasma

We describe a numerical model constructed for the study of the emission ofradiation from relativistic plasma under conditions characteristic, e.g., togamma-ray bursts (GRB's) and active galactic nuclei (AGN's). The model solvesself consistently the kinetic equations for e^\pm and photons, describingcyclo-synchrotron emission, direct Compton and inverse Compton scattering, pairproduction and annihilation, including the evolution of high energyelectromagnetic cascades. The code allows calculations over a wide range ofparticle energies, spanning more than 15 orders of magnitude in energy and timescales. Our unique algorithm, which enables to follow the particledistributions over a wide energy range, allows to accurately derive spectra athigh energies, >100 \TeV. We present the kinetic equations that are beingsolved, detailed description of the equations describing the various physicalprocesses, the solution method, and several examples of numerical results.Excellent agreement with analytical results of the synchrotron-SSC model isfound for parameter space regions in which this approximation is valid, andseveral examples are presented of calculations for parameter space regionswhere analytic results are not available.Comment: Minor changes; References added, discussion on observational status added. Accepted for publication in Ap.