Seasonal-latitudinal distributions of the populations of the states O2(b1, v = 0 - 2) in the daytime mesosphere and lower thermosphere

In the last decade, it was shown that volume emission rates (VMR) for transitions from the levels O₂(b¹Σ⁺_g, v’ = 0 – 2) to the levels O₂(X³Σ^-_g, v’’) can be used as proxies for retrieving the altitude profiles of [O(³P )], [O₃] and [CO₂] in the mesosphere and lower thermosphere (MLT) [1, 2]. Despite the fact that, in single experiments, radiation in the bands 762, 688, and 628 nm corresponding to the abovementioned transitions were observed (e. g., [3]), no systematic measurements of the intensities of these emissions have yet been performed. The main source of excitation of the levels O₂(b¹Σ⁺_g, v’ = 0 – 2) is the energy transfer from the excited O(¹D) atom, along with the resonant absorption of solar radiation in these bands in the mesosphere.

In the framework of the YM2011 model of electronical-vibrational kinetics of the excited products of O₂ and O₃ photolysis, using systematic SABER satellite experimental data on the [O (¹D)] altitude profiles we calculated the altitudinal-latitudinal distributions of the O₂(b¹Σ⁺_g, v’ = 0 – 2) concentrations  and VMR in the corresponding bands, using the 2010 data as an example. It was shown that there is a seasonal dependence of the altitude profiles of the concentrations of excited states O₂(b¹Σ⁺_g, v’ = 0 – 2) obviously related to the seasonal changes of [O(³P)] and [O₃] profiles.

This work was supported by the Russian Foundation for Basic Research  (grant RFBR No. 20-05-00450 A).

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2. Yankovsky V. A., Vorobeva E. V., Manuilova R. O. (2019), New techniques for retrieving the [O(3P)], [O3] and [CO2] altitude profiles from dayglow oxygen emissions: Uncertainty analysis by the Monte Carlo method, Advances in Space Research, 64, 1948–1967, https://doi.org/10.1016/j.asr.2019.07.020

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