  We study the radiative hydrodynamics flow of radiation-driven heat waves in
hot dense plasmas, using approximate self-similar solutions. Specifically, we
have focused on the intermediate regime between pure radiative supersonic flow
and the pure subsonic regime. These two regimes were investigated both using
exact self-similar solutions and numerical simulations, however, most of the
study used numerical simulations, mainly because the radiative heat wave and
the shock regions are not self-similar altogether. In a milestone work [J.
Garnier et al., Phys. Plas., 13, 092703 (2006)], it was found that for a
specific power law dependency temperature profile, a unique exact self-similar
solution exists, that is valid for all physical regimes. In this work we
approximate Garnier's exact solution for a general power-law
temperature-dependency, using simple analytical considerations. This
approximate solution yields a good agreement compared to numerical simulations
for the different thermodynamic profiles within the expected range of validity.
In addition, we offer an approximate solution for the energies absorbed in the
matter, again, for a general power-law temperature profile. Our approximate
self-similar solution for the energy yields very good results comparing to
exact numerical simulations for both gold and $\mathrm{Ta_2O_5}$. We also set a
comparison of our self-similar solutions with the results of an experiment for
radiation temperature measurement in a hohlraum in low-density foams that is
addressed directly, to the intermediate regime, yielding a good agreement and
similar trends. The different models as well as the numerical simulations are
powerful tools to analyze the supersonic-subsonic transition region.
