EXCITATION OF ELECTRONIC STATES AND ATOM IONIZATION BEHIND STONG SHOCK WAVES IN AIR
Essential difficulties are arisen at due selection of ionization rates for oxygen and nitrogen atoms when analyzing structures of the relaxation zone behind strong shock waves (SW) in air plasma (at V > 9 km/c) both for the shock tube experiments and numerical modeling of convective-radiative heating of reentry vehicles because of violation of local thermodynamic equilibrium (LTE) conditions. In general case the atom ionization and relaxation zone structure behind the shock wave cannot be described within the frameworks of conventional models where the Cauchy problem with initial data imposed at the shock is solved using atomic ionization rate due to electron impact depending only electron temperature, because of very complex interaction of the elemental processes in compressed layer. Extreme uncertainties in specification of the shock layer parameters are also arisen at numerical simulation of vehicle flows with Navier-Stokes equations together with mentioned atom ionization rates. This paper demonstrates (on the basis of analysis of available experimental and numerical data on excitation, ionization and radiation processes) that the atom ionization rate by electron impact at high velocities depends on temperature, pressure and a size of considered domain and can be determined only as a result of problem solution using a radiation-collision model. Using such a model we will escape claim of selection of the ionization rate constants as well as engaging additional assumptions on atom partitions throughout excited states.