Abstract
A new type of Martian aurora, characterized by an extended spatial distribution, an altitude lower than the discrete aurora and electron precipitation up to 200keV has been observed following solar activity on several occasions from the MAVEN spacecraft. We describe the results of Monte Carlo simulations of the production of several ultraviolet and violet auroral emissions for initial electron energies extending from 0.25 to 200keV. These include the CO2+ ultraviolet doublet (UVD) at 288.3 and 289.6nm and the Fox–Duffendack–Barker (FDB) bands, CO Cameron and Fourth Positive bands, OI 130.4 and 297.2nm and CI 156.1nm and 165.7nm multiplets. We calculate the nadir and limb production rates of several of these emissions for a unit precipitated energy flux. Our results indicate that electrons in the range 50–200keV produce maximum CO2+ UVD emission below 75km, in agreement with the MAVEN observations. We calculate the efficiency of photon production per unit precipitated electron power. The strongest emissions are the CO2+ FDB, UVD and CO Cameron bands and the oxygen emission at 297.2nm. The metastable a 3Π state which radiates the Cameron bands is deactivated by collisions below about 110km. As a consequence, we show that the Cameron band emission is expected to peak at a higher altitude than the CO2+ UVD and FDB bands. Collisional quenching also causes the intensity ratio of the CO2+ UVD to CO Cameron bands to increase below ∼100km in the energetic diffuse aurora.
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