The brightness of the CO Cameron bands in the martian discrete aurora: A study based on revised cross sections

peer reviewedWe analyze the consequences of the new laboratory measurements of the emissions cross sections of the Cameron bands excited by electron impact on CO2 and CO in the Mars aurora. We use Monte Carlo simulations to investigate the importance of these changes and their dependence on the initial electron energy. The Mars Climate Database (MCD) is used as an input for the temperature and neutral density profiles. Auroral density profiles of O2+, CO+2 and electrons in the aurora are calculated for a range of precipitating electron energies. The total nadir brightness of the Cameron bands is reduced by a factor of 4.5 at 150 eV and 5.1 at 700 eV relative to calculations made with the previously recommended cross section. The relative contributions to the production of the Cameron bands by electron collisions with CO2 and CO are examined. It varies with the CO/CO2 density ratio near the emission peak that depends on the neutral model and season. Dissociative recombination of CO+2 ions provides a contribution between 10% and 45% at the altitude of maximum production of the a 3Π state. The efficiency of the nadir brightness of the Cameron bands is 2.5–3.6 kilorayleighs per incident electron energy flux of 1 mW m-2, with a small dependence on the initial electron energy. Model simulations predict that the intensity ratio of the Cameron bands to the CO+2 UV doublet (UVD) depends on the electron initial energy. It varies from 2.0 at 500 eV to 5.3 at 50 eV, for both Ls = 90° and 225°