Peculiarities of the solar wind interaction with the upper atmospheres of Venus and Mars

Abstract

The direct measurements of the plasma and magnetic fields of Venus and Mars as well as satellite radiooccultation observations of their upper atmospheres and ionospheres reveal some similarities and differences in the overall configuration of the solar wind flow as it streams around these planets. Both planets have very weak magnetic fields as compared with that of the Earth, and their ionospheres are characterized by a similar maximum electron density. However, the Martian ionosphere is protected from the direct action of the solar wind to a greater extent than that at Venus and some properties of the Martian upper ionosphere resemble those of the Earth's upper ionosphere. It is concluded that the Venus ionosphere and induced magnetic field (the draped solar wind magnetic field) are decisive for the formation of the Venus effective obstacle. As to Mars, its intrinsic magnetic field dominates and plays an important role in forming the obstacle and decelarating the solar wind.