Photon transport through plasmas with density and velocity structure

The problem of inverse Compton scattering (ICS) of photons and electrons in plasmas is of importance for high-energy astrophysics. One example is the scattering of photons in an accretion flow. However, most Monte Carlo codes used in this field are not capable of investigating scattering in plasmas with smooth temperature and density gradients, and treating bulk motion is difficult even for simple cases. With the introduction into the field of algorithms associated with nonlinear Monte Carlo codes, these problems are now tractable numerically. Nonlinear Monte Carlo codes can already handle arbitrary velocity structures in a plasma. Here an extension of the algorithm is proposed that enables the calculation of scattering in plasmas with nonconstant density as well as nonconstant temperature and/or bulk motion. Scattering at low optical depths also can be studied. A code using this method can study the ICS problem in a wide variety of accretion flows, and do so exactly. (C) 2001 Academic Press.