Simulating radiation and kinetic processes in relativistic plasmas

TL;DR

This paper introduces a comprehensive numerical code for simulating the complex radiation and kinetic processes in relativistic plasmas of high-energy astrophysical sources, enabling detailed modeling of their emission spectra.

Contribution

The paper presents a new, versatile simulation code that models time-dependent kinetic equations for particles and photons without assuming distribution shapes, including key physical processes.

Findings

Qualitative reproduction of previous results with some detailed differences

Demonstration of the code's capacity through example simulations

Identification of energy thresholds affecting particle acceleration and spectra

Abstract

Modelling the emission properties of compact high energy sources such as X-ray binaries, AGN or gamma-ray bursts represents a complex problem. Contributions of numerous processes participate non linearly to produce the observed spectra: particle-particle, particle-photon and particle-wave interactions. In the past decades, numerical simulations have been widely used to address the key properties of the high energy plasmas present in these sources. This article presents a code that has been designed to investigate these questions. It includes most of the relevant processes needed to simulate the emission of high energy sources. This code solves the time-dependent kinetic equations for homogeneous, isotropic distributions of photons, electrons and positrons. No assumption is made on the shape of these distributions. Have been included so far: syn- chrotron self-absorbed radiation, Compton scattering, pair production/annihilation, e-e and e-p Coulomb collisions and some prescriptions for additional particle heating and acceleration. We also present comparisons with earlier works and some examples to illustrate the code computational capacities. Previous results are reproduced qualitatively but some differences are often found in the details of the particle As a first application of the code, we investigate acceleration by second order Fermi-like processes and we find that the energy threshold for acceleration has a crucial influence on the particle distribution and the emitted spectrum.