Model calculations of nightside ionosphere of Venus - Ionic composition

Model calculations of nightside ion and electron densities have been carried out for the ionosphere of Venus and compared with the results obtained from Pioneer Venus ion mass spectrometer and Venera 9 and 10 radio occultation measurements. The generalized yield spectrum approach has been used for the calculation of ion production rates in the ionosphere of Venus by using measured Venera 9 electron fluxes. Coupled continuity equations for ionic species CO2(+), CO(+), H(+), NO(+), C(+), N2(+), N(+), He(+), O(+) and O2(+) have been solved by assuming photochemical steady state conditions. The results obtained for electron density show good agreement with the measured densities obtained by PVO mass spectrometer. However, at higher altitudes the present results are about a factor two less than the results reported by Venera 9 and 10 measurements. The electron density at the layer peak calculated in the present work is 10,000/cu cm, a value comparable to that reported by Venera 9 and 10 measurements during solar cycle minimum.