Global modeling of thermospheric airglow in the far ultraviolet

摘要

The Global Airglow (GLOW) model has been updated and extended to calculate thermospheric emissions in the far ultraviolet, including sources from daytime photoelectron-driven processes, nighttime recombination radiation, and auroral excitation. It can be run using inputs from empirical models of the neutral atmosphere and ionosphere or from numerical general circulation models of the coupled ionosphere-thermosphere system. It uses a solar flux module, photoelectron generation routine, and the Nagy-Banks two-stream electron transport algorithmto simultaneously handle energetic electron distributions from photon and auroral electron sources. It contains an ion-neutral chemistry module that calculates excited and ionized species densities and the resulting airglow volume emission rates. This paper describes the inputs, algorithms, and code structure of the model and demonstrates example outputs for daytime and auroral cases. Simulations of far ultraviolet emissions by the atomic oxygen doublet at 135.6 nm and the molecular nitrogen Lyman-Birge-Hopfield bands, as viewed from geostationary orbit, are shown, and model calculations are compared to limb-scan observations by the Global Ultraviolet Imager on the TIMED satellite. The GLOW model code is provided to the community through an open-source academic research license. Plain Language Summary The Global Airglow (GLOW) model has been updated and extended to calculate ultraviolet light emitted by the upper atmosphere, including during the day, during the night, and in the aurora. It can be run using inputs from standard climatological models of the upper atmosphere and ionosphere or from complex computer models that describe the dynamics of the ionosphere. It computes energetic electron fluxes from both solar and auroral sources, and it contains a chemistry module that calculates the densities of excited and ionized atoms and molecules, and the resulting airglow emission rates. This paper describes the inputs, algorithms, and code structure of the model and demonstrates example outputs for daytime and the aurora. Simulations of ultraviolet emissions by atomic oxygen and molecular nitrogen, as viewed from geostationary orbit, are shown, and model calculations are compared to observations by the Global Ultraviolet Imager on the TIMED satellite. The GLOW model code is provided to the community through an open-source academic research license.