PHOTOELECTRON FLUXES IN THE MARTIAN IONOSPHERE.

The equilibrium photoelectron distribution in the upper atmosphere of Mars is calculated and compared with a typical theoretical model of the photoelectron distribution in the upper atmosphere of the earth. While the primary photoelectron spectra in Mars' and earth's ionospheres are remarkably similar in spectral shape and finer structure features, the Martian equilibrium photoelectron spectrum is more structured and much softer than the earth's. The equilibrium photoelectron spectrum is used to investigate the loss of the photoelectron kinetic energy to the various constituents of the upper atmosphere of Mars, including the heating of the ambient electron gas. The ionization rates by photoelectron impact are calculated and are found to contribute about 30% to the total ionization rate on Mars. Photoelectron impact excitation is found to contribute 20-30% to the CO//2** plus and CO airglow of Mars.