Radiative Shock Structure

A study is made of plane gas dynamic and transverse magnetogasdynamic shock waves in fully ionized hydrogen at conditions such that radiative processes are significant. The length scale required for a radiative shock wave to be steady is large, and the establishment of a truly steady-state flow is found only for dimensions relevant to astrophysical cases. In the case of such an established flow the Rankine-Hugoniot jump equation (i.e., the relationship between the flow variables in the initial and final states) is analyzed. It is shown that of the twelve roots of this equation only two are physical, corresponding to the super-signal initial and sub-signal final states. The differential equations which describe the above shock waves are analyzed for cases where the shock is optically thick, i.e., the mean free path for absorption of radiation is much smaller than the characteristic lengths for change of the flow variables. A new criterion is given for the validity of this approximation.