The Ionosphere and Upper Atmosphere of Venus

Abstract

The Mariner 10 flyby of Venus has provided us a second close look at the upper atmosphere of a planet which has intrigued aeronomers for a long time. The Mariner 10 payload included an objective grating spectrometer designed to measure airglow radiations from Venus and Mercury in the spectral range 200 to 1700 A at discrete wavelengths corresponding to the resonance radiations of H, He, C, O, Ar, Ne and CO (Broadfoot et al., 1974). The data on the ionosphere and the neutral atmosphere were obtained from the radio-occultation experiment (Howard et al., 1974) whereas an electrostatic analyzer was employed to make in situ measurements of the charged particle environment arotind Venus (Bridge et al., 1974). A highly sensitive dual magnetometer system was employed to measure magnetic fields around Venus, especially in the bow shock region (Ness et al., 1974). A number of questions raised by the Mariner 5 flyby in 1967 have been answered while many more new ones have evolved. Far UV spectra (1200–1900 A) of Venus with moderate spectral resolution (∼ 20 A) have also been obtained from a number of rocket experiments (Moos et al., 1969; Moos and Rottman, 1971; Rottman and Moos, 1973). These spectra have lead to the identification of several minor constituents in the upper atmosphere. This paper summarizes the current understanding of the upper atmosphere and ionosphere of Venus and its interaction with solar wind.