Continuum radiation from nonisothermal hydrogen plasmas

Abstract

In this account of an investigation of the continuum radiative flux from nonisothermal stagnation shock layers composed of a hydrogen plasma, the general equations for the composition are derived and the Rankine-Hugoniot equations are simplified and solved to give the thermodynamic conditions in the shock layers. The radiative flux is calculated by considering ground to free state radiative transitions in atomic hydrogen for conditions roughly representing those of a space probe entering Jupiter's atmosphere. The influence of Mach number, ambient density (altitude), spectral variation of the radiation absorption coefficient, shock layer thickness, excited state radiation, and temperature profiles are examined. The results show that not only the composition but also the equilibrium temperature behind the shock wave is essentially determined by considering only the ground state of atomic hydrogen. The excited state is largely responsible for the emitted radiation near the shock where the temperature is high, while the ground state produces the radiation in the cooler region of the shock layer near the body. In addition it is shown that the temperature profile is very important in determining the radiative flux reaching the body. The isothermal approximation not only overestimates the radiative flux but also influences the spectral distribution of the radiation reaching the body.