Hot oxygen atoms in the upper atmosphere of Venus

Abstract

The energy distribution of “hot” oxygen atoms in the upper atmosphere of Venus was calculated using two different numerical methods. The two different approaches were based on 1) 2‐stream transport and 2) diffusion equation considerations. Dissociative recombination of molecular oxygen ions and charge exchange of atomic oxygen ions with the neutral hydrogen and oxygen gas were the source terms considered; the calculations show that the dissociative recombination term is the dominant one. The altitude distribution of the hot oxygen atoms above the exobase was also calculated and compared with measurements by the Pioneer Venus Orbiter Ultraviolet Spectrometer. The calculated densities show an altitude dependence similar to that obtained by the measurements, but are larger by a factor of about four to five. We find that the concentration of hot oxygen atoms is comparable to or exceeds that of thermal hydrogen atoms throughout much of the dayside exosphere.