Journal cover Journal topic
Annales Geophysicae Sun, Earth, planets, and planetary systems An interactive open-access journal of the European Geosciences Union
https://doi.org/10.5194/angeo-2018-5
© Author(s) 2018. This work is distributed under
the Creative Commons Attribution 4.0 License.
Regular paper
06 Feb 2018
Review status
This discussion paper is a preprint. It is a manuscript under review for the journal Annales Geophysicae (ANGEO).
Variations of the 630.0 nm airglow emission with meridional neutral wind and neutral temperature around midnight
Chih-Yu Chiang1, Sunny Wing-Yee Tam1, and Tzu-Fang Chang1,2 1Institute of Space and Plasma Sciences, National Cheng Kung University, Tainan 70101, Taiwan
2Institute for Space-Earth Environmental Research, Nagoya University, Nagoya 464-8601, Japan
Abstract. Enhancements in 630.0 nm airglow around midnight at equatorial latitudes were observed by many optical observations. Such features had been suggested as the signature of thermospheric midnight temperature maximum (MTM) effect, which was associated with temperature and meridional neutral winds. This study investigates the influence of neutral temperature and meridional neutral wind on the volume emission rates of the 630.0 nm nightglow. We utilize the SAMI2 model to simulate the charged and neutral species at the 630.0 nm nightglow emission layer under different temperatures with and without the effect of neutral wind. The results show that the neutral wind is more efficient than temperature variation in affecting the nightglow emission rates. However, the emission rate features a local maximum in its variation with the temperature. Two kinds of tendencies can be seen regarding the temperature that corresponds to the turning point, which is named the turning temperature (Tt) in this study: firstly, Tt decreases with the emission rate for the same altitude; secondly, for approximately the same emission rate, Tt increases with the altitude.

Citation: Chiang, C.-Y., Tam, S. W.-Y., and Chang, T.-F.: Variations of the 630.0 nm airglow emission with meridional neutral wind and neutral temperature around midnight, Ann. Geophys. Discuss., https://doi.org/10.5194/angeo-2018-5, in review, 2018.
Chih-Yu Chiang et al.
Chih-Yu Chiang et al.
Chih-Yu Chiang et al.

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Short summary
Based on our simulation results, both temperature change and meridional neutral wind could cause the 630.0 nm nightglow intensity to vary while the latter is more effective. An unexpected aspect of the results is the non-monotonic dependence of the emission rate on temperature, featuring a turning point as the temperature changes. Our findings of these turning temperature tendencies can guide future modeling attempts to match the observed nightglow brightness intensities.
Based on our simulation results, both temperature change and meridional neutral wind could cause...
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