A 2-dimensional model of the Venus ionosphere

The Pioneer Venus observations show a peak in the O2+ concentration at ∼170 km altitude in the dayside ionosphere of Venus. In this thesis, the 2-dimensional MHD equations are solved in a self-consistent manner, as an extension to the 1-dimensional model by Cloutier et al. (1987), to present a global model of the Venus dayside ionosphere for solar zenith angles (SZA) ≤ 60 degree. The model describes, by calculating vertical profiles at different SZA, ion densities, magnetic field magnitudes, and ion velocities. The model shows that the O2+ peak, at ∼170 km altitude, occurs throughout the dayside ionosphere as observed by the Orbiter Ion Mass Spectrometer (OIMS). The velocity field, which affects the ion distributions, is mainly tangential near the ionopause and radial for altitudes below 200 km. The downward flow accelerates, near 170 km altitude, due to collisional interactions with the neutral atmosphere, and removes the O2+ densities to lower altitudes, thus, producing the bump observed in the altitude profile