  The effects of radiation on the structure of shocks in a fully-ionized plasma
are investigated by solving the steady-state fluid equations for ions,
electrons, and radiation. The electrons and ions are assumed to have the same
bulk velocity but separate temperatures, and the radiation is modeled with the
gray-diffusion approximation. Both electron and ion conduction are included, as
well as ion viscosity. When the material is optically thin, three-temperature
behavior occurs. When the diffusive flux of radiation is important but
radiation pressure is not, two-temperature behavior occurs, with the electrons
strongly coupled to the radiation. Since the radiation heats the electrons on
length scales that are much longer than the electron-ion Coulomb coupling
length scale, these solutions resemble radiative shock solutions rather than
plasma shock solutions that neglect radiation. When radiation pressure is
important, all three components are strongly coupled. Results with constant
values for the transport and coupling coefficients are compared to a full
numerical simulation with a good match between the two, demonstrating that
steady shock solutions constitute a straightforward and comprehensive
verification test methodology for multi-physics numerical algorithms.
