Analytical study and structure of a stationary radiative shock

In this paper we study the radiative shock that arises in certain situation s in astrophysics (among others, supernovae, accretion flows, and stars for mation). However, it is clear that the high-energy lasers (LIL, LMJ, NIF) w ill produce plasma flows with hydrodynamics dominated by radiation. Usually , only the radiation flux is considered, and the radiation pressure and ene rgy are neglected. In this paper, in addition to the radiation flux, we tak e into account the total (matter plus radiation) energy density and pressur e. We derive the corresponding generalized Rankine-Huguoniot equations, and it turns out that we can get analytically the structure of the radiative s hock. It is shown that three distinct regimes arise; when the Mach number i ncreases (but is small enough), the shock evolves from a continuous structu re to a discontinuous one (a discontinuity appears between the shocked medi um and the fluid at rest). It is seen then, that this discontinuity disappe ars for very high values of the Mach number. These behaviors are due to the presence of radiation. Moreover, a precursor develops into the unshocked m edium, and scaling laws are derived to obtain the width of the shock and th e length of the precursor in terms of the Mach number. Finally, the assumpt ion of the LTE approximation is examined.