Photo-ionization balance and ion composition model on the ionospheres of Mars and Venus

Photo-ionization rates on the ionospheres of Mars and Venus have been computed using the latest available data such as Hinteregger solar fluxes, photo-ionization and photo-absorption cross-sections and the neutral atmospheric models. Photochemical equilibrium has been assumed in the height range 100-300 km. The derived Ne(h) profiles are compared with the observed Ne(h) profiles. There is thermal equilibrium (Te=Tg) in the case of the Martian ionosphere. However, there is thermal imbalance (Te>Tg) on the Venusian ionosphere above 160 km. Ion density profiles have been derived by the application of appropriate photochemistry. There is an excellent agreement between the observed and computed ion density profiles below 200 km in both the ionospheres. (author). 24 refs., 7 figs., 2 t abs