The ionosphere of Titan: Ideal diurnal and nocturnal cases

We have solved a stationary Boltzmann transport equation to describe the io nosphere of Titan in two simple cases. The first one deals with the satelli te being outside the Kronian magnetosphere on the dayside of Saturn, which happens under strong solar wind conditions. In that case, the main energy s ource of ionization is the solar photons. We show the effect of the photoio nization and the secondary ion production for a solar zenith angle of 45 de grees. The electron production peaks at 25 electrons s(-1) cm(-3) around 10 00 km, We estimate the electron density from a comprehensive chemical code. This electron density is then compared with the one computed from a simple recombination model. Finally, we determine the intensity of nitrogen emiss ions, which are compared to the Voyager 1 measurements. In the second case, the satellite is inside Saturn's magnetosphere. We show the effect of the ionization due to electron precipitation at night, above the polar regions. The input electron flux is measured by the Voyager prob es, gathered from several instruments on board. A simple Kappa distribution is given to model a mean electron flux precipitating on Titan, We show tha t the electron production ranges between 1 to 5 electrons s(-1) cm(-3) betw een about 550 and 650 km. The electron production due to the photoionizatio n above the pole is evaluated and compared to the effect of the kronian ele ctron precipitation. (C) 1999 Academic Press.