Atomic carbon in the atmosphere of Venus

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.