Time-dependent modeling of radiative processes in hot magnetized plasmas

TL;DR

This paper introduces a comprehensive time-dependent simulation code for radiative processes in hot magnetized plasmas, accurately modeling complex interactions without approximations, applicable to phenomena like black hole accretion disks and gamma-ray bursts.

Contribution

The authors developed a novel, exact numerical code solving coupled kinetic equations for photons and leptons, covering all energy regimes and processes without simplifying assumptions.

Findings

Successfully modeled non-thermal pair cascades in blackbody radiation.

Demonstrated synchrotron self-absorption as a thermalization mechanism.

Simulated time evolution of pairs and spectra relevant to gamma-ray bursts.

Abstract

Numerical simulations of radiative processes in magnetized compact sources such as hot accretion disks around black holes, relativistic jets in active galaxies and gamma-ray bursts are complicated because the particle and photon distributions span many orders of magnitude in energy, they also strongly depend on each other, the radiative processes behave significantly differently depending on the energy regime, and finally due to the enormous difference in the time-scales of the processes. We have developed a novel computer code for the time-dependent simulations that overcomes these problems. The processes taken into account are Compton scattering, electron-positron pair production and annihilation, Coulomb scattering as well as synchrotron emission and absorption. No approximation has been made on the corresponding rates. For the first time, we solve coupled integro-differential kinetic equations for photons and electrons/positrons without any limitations on the photon and lepton energies. A numerical scheme is proposed to guarantee energy conservation when dealing with synchrotron processes in electron and photon equations. We apply the code to model non-thermal pair cascades in the blackbody radiation field, to study the synchrotron self-absorption as particle thermalization mechanism, and to simulate time evolution of stochastically heated pairs and corresponding synchrotron self-Compton photon spectra which might be responsible for the prompt emission of gamma-ray bursts. Good agreement with previous works is found in the parameter regimes where comparison is feasible, with the differences attributable to our improved treatment of the microphysics.