**5. Conclusions**

The fluid dynamic response of the solar wind that interacts with planetary ionospheres is ultimately produced by wave-particle interactions inferred from the observation of frequent oscillations in magnetic field profiles measured in the Venus wake [16–18]. As a whole such interactions provide a mechanism to transfer momentum between both ion populations and thus erode the upper layers of the Venus ionosphere [2]. That process implies in turn local plasma heating [19, see Fig. 35; 20, 21] and the removal of ionospheric plasma in the form of channels or ducts that extend downstream along the Venus wake [22, 23]. These various features are in agreement with phenomena observed in fluid dynamic problems and provide an account of measurements conducted in the Venus wake with various spacecraft. The identification of vortex structures in the Venus wake whose position and width varies during the solar cycle provides a remarkable result that justifies the importance of the fluid dynamic approach.
