The densities of atomic carbon in the Venusian thermosphere are computed for a model which includes both chemistry and transport. The maximum density of C is 2.8×107 cm−3 near 150 km for an assumed O2 mixing ratio of 1×10−4. Photoionization of atomic carbon is found to be the major source of C+ above 200 km, and resonance scattering of sunlight by atomic carbon may be the major source of the C I emissions at 1561 Å, 1657 Å, and 1931 Å. The computed C+ densities are found to be in substantial agreement with those measured by Pioneer Venus.
Fox, J. L.
(1982). Atomic Carbon in the Atmosphere of Venus. Journal of Geophysical Research: Space Physics, 87 (A11), 9211-9216.