Variability of Venusian hot oxygen corona during a solar cycle

Because Venus has no strong planetary magnetic field, the fast-flowing solar wind plasma can propagate to regions close to the planet. Therefore, understanding the distribution of hot atomic oxygen in the corona and the resulting pickup of oxygen ions is essential in characterizing the dynamics of the Venusian upper atmosphere and that of the overall planet’s interaction with the plasma of the ambient solar wind.

The work presented here is focused on characterizing how the hot oxygen corona changes during a solar cycle. That involves numerical modeling not only of the corona itself but also the thermosphere and ionosphere. Each of the models employed in this study covers a physical sub-domain such that the coupled combination of the codes self-consistently describes the studied environment. The physical sub-domains are organized such that (1) VTGCM produces a self-consistent calculation of the thermosphere/ionosphere providing spatial distribution of the thermal oxygen as well as all the dominant species, (2) the calculated distribution of the major species is further used to model the three-dimensional hot oxygen corona with AMPS. These results will be used as input to a full MHD simulation of the solar wind/Venus interaction.

Here, we present recent results of a hot oxygen corona calculation in 3D and its variation with solar activity. We use a 3D thermosphere/ionosphere model to calculate both the source of hot O in the dissociative recombination of O₂⁺ ions and the upper thermosphere distributions of CO₂, CO, N₂, and thermalized O through which the nascent hot O must pass before reaching the corona. Support for this work is provided by NASA grant 80NSSC17K0728 from the Solar System Workings program.