Comparison of Calculated and Measured Ion Densities on the Dayside of Venus

Data from the Pioneer Venus ion mass spectrometers are compared with model calculations of the ion density distributions appropriate for daytime conditions. The model assumes diffusive equilibrium upper boundary conditions for the major ions (O₂{}⁺, O⁺, CO₂{}⁺, He⁺, and H⁺); the agreement between the calculated and measured gross behavior of these ions is reasonably good except for H⁺. which may be influenced strongly by convective transport processes. The distributions of five minor ions (C⁺, N⁺, NO⁺, CO⁺, and N₂{}⁺) are also calculated for the chemically controlled region lesssim 200 kilometers); the agreements are, in general, poor, an indication that our present understanding of the Venus minor ion chemistry is still incomplete.