The chemistry of excited NO⁺ in an aurora

The six most significant production and seven most significant loss mechanisms are identified for NO + ( a ³Σ) in the aurora. Rate constants are given for these reactions as well as for the 14 most important reactions competing with the production of NO + ( a ). Using available data and certain crucial deductions on chemical reaction rates to simulate a number of altitude profiles, we have concluded that the two predominant sources of NO + ( a 3 Σ) are probably N + + O 2 → NO + ( a ) + O and N 2 + + NO → NO + ( a ) + N 2 . Radiative decay is not the primary loss mechanism but can dominate above 150 km. Destruction via charge exchange with N 2 and O are most important below 150 km. Total radiation in the a 3 Σ– X ¹Σ transition is estimated to be between 35 R and 350 R for a model aurora of 78 ergs cm −2 s −1 energy input, which is nearly IBC III in intensity.