Infrared emissions from nitric oxide (NO) are the dominant source of radiative cooling between 120 and 200 km and play an important role in determining the energy budget of the Earth's upper atmosphere. The emission arises as a consequence of producing vibrationally excited NO, either by collisions with energetic atomic oxygen or via the reaction of atomic nitrogen with molecular oxygen. The latter process is a potentially important source of cooling, as it can excite the higher vibrational levels (v ≥ 2) of nitric oxide, resulting in the emission of multiple photons. This chemiluminescent emission has been modeled by calculating the level populations of NO(v ≤ 10) considering production from the reaction of N(2D) and N(4S) with O2, along with interlevel cascade due to radiative deexcitation and collisional quenching. We integrate this model into the NCAR TIE‐GCM (Thermosphere‐Ionosphere‐Electrodynamics General Circulation Model) to calculate the contribution of chemiluminescence to infrared emissions from NO in the thermosphere. For day 80 of 2003, it is shown that chemiluminescence accounts for 15–30% of the total column emissions from NO in the sunlit thermosphere between ±50° latitude. More than 60% of the chemiluminescence is produced from v ≥ 3, indicating that these vibrational levels are an important source of thermospheric cooling. Model calculations of the first overtone emission (Δv = 2) are shown to be in agreement with measurements by the Cryogenic Infrared Radiance Instrumentation for Shuttle (CIRRIS‐1A) experiment. A computationally inexpensive parameterization which calculates the chemiluminescence from v ≤ 10 within 5% of the full calculation is also presented.

An accurate estimate of the energy budget (heating and cooling) of the ionosphere and thermosphere, especially during space weather events, has been a challenge. The abundance of nitric oxide (NO), a minor species in the thermosphere, is an important component of energy balance here because its production comes from energy sources able to break the strong bond of molecular nitrogen, and infrared emissions from NO play an important role in thermospheric cooling. Recent studies have significantly improved our understanding of NO chemistry and its relationship to energy deposition in the thermospheric photochemical reactions. In this study, the chemical scheme in the Global Ionosphere‐Thermosphere Model (GITM) is updated to better predict the lower thermospheric NO responses to solar and geomagnetic activity. We investigate the sensitivity of the 5.3‐μm NO emission to F10.7 and Ap indices by comparing the global integrated emission from GITM with an empirical proxy derived from the Sounding of the Atmosphere using Broadband Emission Radiometry measurements. GITM's total emission agrees well within ±20% of the empirical values. The updated chemistry scheme significantly elevates the level of integrated emission compared to the previous scheme. The inclusion of N2(A)‐related production of NO contributes an additional 5–25% to the emission. Localized enhancement of ~70% in column density and a factor of 3 in column emission are simulated at a moderate geomagnetic level.

Recent work has indicated the presence of a nitric oxide (NO) product channel in the reaction between the higher vibrational levels of the first electronically excited state of molecular nitrogen, N 2 (A 3 Σ + u ), and atomic oxygen. A steady-state model for the N 2 (A) vibrational distribution in the terrestrial thermosphere is here described and validated by comparison with N 2 A-X, Vegard-Kaplan dayglow spectra from the Ionospheric Spectroscopy and Atmospheric Chemistry spectrograph. A computationally cheaper method is needed for implementation of the N 2 (A) chemistry into time-dependent thermospheric models. It is shown that by scaling the photoelectron impact production of ionized N 2 by a Gaussian centered near 100 km, the level-specific N 2 (A) production rates between 100 and 200 km can be reproduced to within an average of 5%. This scaling, and thus the N 2 electron impact ionization/excitation ratio, is nearly independent of existing uncertainties in the 2-20 nm solar soft X-ray irradiance. To investigate this independence, the N 2 electron-impact excitation cross sections in the GLOW photoelectron model are replaced with the results of Johnson et al. (2005, https://doi.org/10.1029/2005JA011295) and the multipart work of Malone et al. (2009 https://doi.org/10.1103/PhysRevA.79.032704) (Malone, Johnson, Young, et al., 2009, https://doi.org/10.1088/0953-4075/42/22/225202; Malone, Johnson, Kanik, et al., 2009, https://doi. org/10.1103/PhysRevA.79.032705; Malone et al., 2009, https://doi.org/10.1103/PhysRevA.79. 032704), together denoted J05M09. Upon updating these cross sections it is found that (1) the total N 2 triplet excitation rate remains nearly constant; (2) the steady state N 2 (A) vibrational distribution is shifted to higher levels; (3) the total N 2 singlet excitation rate responsible for the Lyman-Birge-Hopfield emission is reduced by 33%. It is argued that adopting the J05M09 cross sections supports (1) the larger X-ray fluxes measured by the Student Nitric Oxide Explorer (SNOE) and (2) a temperature-independent N 2 (A)+O reaction rate coefficient. Plain Language Summary Plain Language Summary Theoretical modeling of nitric oxide(NO) in the thermosphere has historically been underestimated in comparison with measurements. A new chemical source of NO has been proposed, but to accurately incorporate it into existing models requires a fast way of calculating the electronic and vibrational temperature of the reacting nitrogen gas. It is shown in this work that this can be done by using the N 2 ionization rate as a proxy and that this has the added benefit of being independent of existing unknowns regarding the solar flux at X-ray wavelengths. These results are further discussed in light of recent measurements by the atomic and molecular physics community concerning standard thermospheric diagnostic emissions, particularly the N 2 Lyman-Birge-Hopfield emission. Use of these new cross sections in thermospheric models is found to have significant implications for our understanding of the energy budge...

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