Osup++/sup in the Venusian Ionosphere

Altitude profiles of the O++ densities in the Venusian ionosphere are computed, using a neutral model based on measurements made by the Pioneer Venus Orbiter mass spectrometer for daytime conditions. Double photoionization of atomic oxygen is the most important source of O++. O++ ions are lost by charge transfer to O, N2 and probably to CO2 and CO. The calculated profiles agree well with the ion densities measured by the PVO ion mass spectrometer. Dissociative charge transfer of O++ to N2 is found to be an important source of N+ at high altitudes. The effect of O++ on the ion chemistry is discussed.