Comparison of the Thermospheric Nitric Oxide Emission Observations and the Global Ionosphere-Thermosphere Model (GITM) Simulations: Sensitivity to Solar and Geomagnetic Activities

TL;DR

This study improves the GITM model's prediction of thermospheric nitric oxide emissions by updating its chemistry scheme and analyzing sensitivity to solar and geomagnetic activity, achieving better agreement with observations.

Contribution

The paper introduces an updated chemistry scheme in GITM that enhances the accuracy of NO emission predictions during space weather events.

Findings

GITM's total NO emission agrees within 20% of empirical data.

Updated chemistry increases predicted NO emission levels.

N2(A)-related production adds 5-25% to NO emission.

Abstract

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-micron 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 three in column emission are simulated at a moderate geomagnetic level.