Browsing by Author "McGary, John Edward"

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    A two-dimensional model of the Venus ionosphere
    (1988) McGary, John Edward; Cloutier, Paul A.
    The Pioneer Venus observations show a peak in the O$\sb2\sp+$ concentration at $\sim$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) $\leq$ 60$\sp\circ$. The model describes, by calculating vertical profiles at different SZA, ion densities, magnetic field magnitudes, and ion velocities. The model shows that the O$\sb2\sp+$ peak, at $\sim$170 km altitude, occurs throughout the dayside ionosphere as observed by the Orbiter Ion Mass Spectrometer (OIMS). The velocity field, which affects the ion distributions, is mainly tangential near the ionopause and radial for altitudes below 200 km. The downward flow accelerates, near 170 km altitude, due to collisional interactions with the neutral atmosphere, and removes the O$\sb2\sp+$ densities to lower altitudes, thus, producing the bump observed in the altitude profile.
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    CONVECTION IN THE VENUS IONOSPHERE
    (1987) McGary, John Edward
    Convective studies involving ion flow in the Venus dayside ionosphere are used to understand the nature of the observed O$\sb2\sp+$ distribution. Flows are modeled (not calculated) from previous data and theory which are incorporated to determine the ion distributions for O$\sp+$, CO$\sb2\sp+$, and O$\sb2\sp+$. Current understanding of ion chemistry and related parameters are used in solving the continuity equation in two dimensions to provide ion profiles at different solar zenith angles. To explain the O$\sb2\sp+$ distribution, downward flow with speeds of approximately 500 m/s are required.