Kinetic Modeling of Suprathermal Nitrogen Atoms in the Atmosphere of Titan: II. Escape Due to Dissociation Processes
Shematovich, V. I.
Astronomicheskii Vestnik, vol. 33, p. 32 (1999)


The processes of molecular-nitrogen dissociation in the upper atmosphere of Titan are an important source of suprathermal nitrogen atoms. The dissociation-produced nitrogen atoms are characterized by an excess of kinetic energy and, accordingly, play an important role in the dynamical processes of the hot nitrogen- corona formation and of nonthermal escape of gas to Saturn's magnetosphere. This study is based on a detailed investigation of the kinetics of suprathermal-nitrogen-atom production through the processes of dissociation and dissociative ionization of molecular nitrogen by hard solar UV radiation and by the accompanying flux of high-energy photoelectrons (Shematovich, 1998). On the basis of a stochastic-simulation method, a numerical solution is obtained to the Boltzmann equations for the transport and the collisional kinetics of suprathermal nitrogen atoms in the ground state and in an electronic excitation state in Titan's upper atmosphere. In this way, steady-state nonequilibrium kinetic-energy distribution functions are calculated for the thermosphere-exosphere transition region. From these characteristics, the role of the processes of molecular-nitrogen dissociation in the formation of Titan's hot nitrogen corona is estimated, as well as the contribution of these processes to the flux of nitrogen atoms escaping Titan's atmosphere.