A model of the Venus ionosphere

Results of model calculations of the Venus ionosphere from 120 to 300 km are presented. The chemical scheme and reaction rates used are the same as given by Kumar and Hunten (1974) except that the electron temperature dependence of the dissociative recombination rates is taken into account. Calculations are made for low and high atomic oxygen models in which the O/CO2 ratios are 0.4% and 4% respectively at 140 km, and the results agree well in shape and magnitude with the Mariner 5 and 10 occultation results in the chemically controlled region. Reasonable agreement is obtained at higher altitudes if diffusive equilibrium and high vertical flow velocities (10 km/s) are assumed as upper boundaries for the Mariner 5 and 10 conditions respectively, although solar wind-ionosphere interactions are considered to be the controlling mechanism for the Mariner 10 results.