The Aeronomy of the Upper Atmosphere of Venus
Abstract
Density profiles for CO, O, and O 2 in the Cytherean atmosphere above 90 km are plotted with eddy diffusion coefficient ( K) as a parameter, subject to the constraint that the mixing ratios of CO and O 2 approach their observed value or values under the observed upper limit at the lower boundary. It is then shown that the value of K puts upper limits on the amount of hydrogen (in the form of H 2O, HCl, and H 2) the atmosphere near 90km can contain. This value is a function of the density and temperature of hydrogen at the critical level and the magnitude of the total escape flux, where unspecified flux mechanisms other than thermal are postulated ad hoc. In general these constraints call for large values of K to accomodate the atomic hydrogen produced by measured mixing ratios of HCl and H 2O. Hence they constrain thee amount of O in the upper atmosphere to values well under 1% at 130 km unless there are very large hydrogen escape fluxes, 10 7 cm -2sec -1 or larger. The freedom to assume arbitrary amounts of H 2 in the atmosphere is also restricted. We suggest either very effective escape mechanisms—despite low exospheric hydrogen densities—or novel excitation mechanisms for O(3 3S) and O(3 5S) in the upper atmosphere.
- Publication:
-
Icarus
- Pub Date:
- February 1975
- DOI:
- 10.1016/0019-1035(75)90092-5
- Bibcode:
- 1975Icar...24..148L
- Keywords:
-
- Aeronomy;
- Atmospheric Composition;
- Gas Dissociation;
- Jeans Theory;
- Upper Atmosphere;
- Venus Atmosphere;
- Airglow;
- Atmospheric Chemistry;
- Atmospheric Models;
- Atomic Excitations;
- Atomic Spectra;
- Hydrogen Atoms;
- Mixing Length Flow Theory;
- Oxygen Spectra;
- Venus Clouds