  Modeling plasma physical processes in astrophysical context demands for both
detailed kinetics and large scale development of the electromagnetic field
densities.
  We present a new framework for modeling plasma physics of hot tenuous plasmas
by a two-split scheme, in which the large scale fields are modeled by means of
a particle-in-cell (PIC) code, and in which binary collision processes and
single-particle processes are modeled through a Monte-Carlo approach. Our novel
simulation tool -- the PhotonPlasma code -- is a unique hybrid model; it
combines a highly parallelized (Vlasov) particle-in-cell approach with
continuous weighting of particles and a sub-Debye Monte-Carlo binary particle
interaction framework.
  As an illustration of the capabilities we present results from a numerical
study of Gamma-Ray Burst - Circumburst Medium interaction and plasma
preconditioning via Compton scattering. We argue that important microphysical
processes can only viably be investigated by means of hybrid codes such as the
PhotonPlasma code.
  Our first results from 3D simulations with this new simulation tool suggest
that magnetic fields and plasma filaments are created in the wakefield of
prompt gamma-ray bursts. Furthermore, the photon flux density gradient impacts
on particle acceleration in the burst head and wakefield. We discuss some
possible implications of the circumburst medium being preconditioned for a
trailing afterglow shock front. We also discuss important improvements for
future studies of GRB wakefields processes, using the PhotonPlasma code.
