Atmosphere of Venus
In 1761, Russian polymath Mikhail Lomonosov observed an arc of light surrounding the part of Venus off the Sun's disc at the beginning of the egress phase of the transit and concluded that Venus has an atmosphere. In 1940, Rupert Wildt calculated that the amount of CO in the Venusian atmosphere would raise surface temperature above the boiling point for water. This was confirmed when Mariner 2 made radiometer measurements of the temperature in 1962. In 1967, Venera 4 confirmed that the atmosphere consisted primarily of carbon dioxide.
Atmosphere of Venus
At the subsolar point the bow shock stands 1900 km (0.3 R, where R is the radius of Venus) above the surface of Venus. This distance was measured in 2007 near the solar activity minimum. Near the solar activity maximum it can be several times further from the planet. The magnetopause is located at the altitude of 300 km. The upper boundary of the ionosphere (ionopause) is near 250 km. Between the magnetopause and ionopause there exists a magnetic barrier—a local enhancement of the magnetic field, which prevents solar plasma from penetrating deeper into the Venusian atmosphere, at least near solar activity minimum. The magnetic field in the barrier reaches up to 40 nT. The magnetotail continues up to ten radii from the planet. It is the most active part of the Venusian magnetosphere. There are reconnection events and particle acceleration in the tail. The energies of electrons and ions in the magnetotail are around 100 eV and 1000 eV respectively.