Effect of the NO concentration on the ratio I₅₅₇.₇/I₄₂₇.₈ in auroras

Abstract

We have examined the effect of the nitrogen oxide concentration on the ratio between λ557.7 nm and λ427.8 nm emission intensities in auroras caused by precipitating electron fluxes, using the numerical simulation method. The ratio I₅₅₇.₇/I₄₂₇.₈ has been shown to strongly depend on the NO concentration: the ratio decreases from 7 to 2 with increasing NO maximum concentration at the height profile from 10⁷ to 3·10⁹. This fact is in satisfactory agreement with experimental data.The effect of nitric oxide on the ratio has been demonstrated to occur through the excitation channel of the emission λ557.7 nm, namely, the dissociative recombination of the molecular oxygen ion O⁺₂+eₜₕ due to the ion deactivation by collision reaction with nitric oxide O⁺₂+NO.