Production of hot nitrogen atoms in the martian thermosphere

The energy and altitude distributions for nitrogen atoms produced from photodissociation of N2 and dissociative recombination of N+2 have been computed for the low and high solar activity martian thermospheres. We find that the fraction of nitrogen atoms with E > E esc at the exobase is ∼ 2.5 % for photodissociation as compared to ∼ 22.6 % for dissociative recombination. However, the peak magnitudes of the production rate profiles for dissociative recombination are a factor of ∼1000 and ∼200 times smaller than those of photodissociation at low and high solar activities, respectively. Thus, our findings suggest that photodissociation of N2 is the dominant escape mechanism for atomic nitrogen for both the low and high solar activity martian thermospheres. The general consensus in the field prior to these research results was that dissociative recombination of N+2 was the main escape mechanism. We find that it is the dissociation of N2 along repulsive states that results in the production of very energetic nitrogen atoms.