Global hybrid simulation of the solar wind interaction with the dayside of Venus

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Abstract
We present a 3‐dimensional global hybrid simulation of the interaction of the solar wind with the entire dayside of Venus. The model obstacle is half the size of Venus, and planetary ion mass loading is included self‐consistently. Results are compared to observations as well as to results from gasdynamic convected field modeling. Magnetic field magnitudes and bulk flow speeds along the planet‐Sun line are comparable in both models, but only the hybrid model reproduces the experimentally observed magnetic barrier proton density depletions. The finite gyroradius of the planetary pickup ions causes a number density asymmetry in the direction of the convective (−V×B) electric field, as predicted and observed. Mass addition consistent with photoionization of the planetary neutral hot oxygen corona has little effect on the geometry of the shock, including the subsolar and terminator shock altitudes. Mass addition rates well in excess of likely values are required to significantly affect the model shock geometry. The hybrid model results imply that oxygen ions originating deep within the dayside Venus magnetic barrier are nearly fluidlike while oxygen ions produced higher on the dayside, at much lower densities, behave more as test particles. Gasdynamic modeling incorporating both fluid and test particle mass addition reproduces the O+ terminator escape flux (a few times 1024 s−1) found in the hybrid model and inferred from observations, but underestimates the escape region spatial extent. The hybrid model predictions include a shock asymmetry dependent on the upstream IMF orientation, asymmetries in the magnetic barrier position and field magnitude, an asymmetry in pickup ion speed altitude profiles, and a finite gyroradius effect asymmetry in pickup ion number density caused by field draping.

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