Nonequilibrium processes and their influence on the structure of inner coma. I. Radiative excitation of water molecules.

Results of modelling of 1-D unsteady water vapor outlow from a cometary surface with allowance for the interaction between solar radiation and the water molecules are presented. To analyze the vibrational and rotational excitation of the H₂O molecule model has been used which includes infrared rovibrational pumping by the solar radiation flux, thermal excitation by collisions and radiation trapping in the rotational and rovibrational lines. The dynamics of the water vapor stream is described by the Euler equations with source terms responsible for the interaction of gas and radiation. Coupled governing gasdynamic and relaxation kinetic equations are solved using factorization over the physical processes. The results of calculations demonstrate the consequence of establishing of the steady flow in the inner coma.