Exospheric Temperature Measured by NASA-GOLD Under Low Solar Activity: Comparison With Other Data Sets

Jaeheung Park; Joseph S Evans; Richard W Eastes; Jerry D Lumpe; Jose van den Ijssel; Christoph R Englert; Michael H Stevens

doi:10.1029/2021JA030041

Exospheric Temperature Measured by NASA-GOLD Under Low Solar Activity: Comparison With Other Data Sets

J Geophys Res Space Phys. 2022 Mar;127(3):e2021JA030041. doi: 10.1029/2021JA030041. Epub 2022 Mar 28.

Authors

Jaeheung Park^{1

2}, Joseph S Evans³, Richard W Eastes⁴, Jerry D Lumpe⁵, Jose van den Ijssel⁶, Christoph R Englert⁷, Michael H Stevens⁷

Affiliations

¹ Space Science Division Korea Astronomy and Space Science Institute Daejeon South Korea.
² Department of Astronomy and Space Science Korea University of Science and Technology Daejeon South Korea.
³ Computational Physics Inc. Springfield VA USA.
⁴ Laboratory for Atmospheric and Space Physics University of Colorado Boulder Boulder CO USA.
⁵ Computational Physics Inc. Boulder CO USA.
⁶ Faculty of Aerospace Engineering Delft University of Technology Delft The Netherlands.
⁷ Space Science Division U.S. Naval Research Laboratory Washington DC USA.

Abstract

Exospheric temperature is one of the key parameters in constructing thermospheric models and has been extensively studied with in situ observations and remote sensing. The Global-scale Observations of the Limb and Disk (GOLD) at a geosynchronous vantage point provides dayglow limb images for two longitude sectors, from which we can estimate the terrestrial exospheric temperature since 2018. In this paper, we investigate climatological behavior of the exospheric temperature measured by GOLD. The temperature has positive correlations with solar and geomagnetic activity and exhibits a morning-afternoon asymmetry, both of which agree with previous studies. We have found that the arithmetic sum of F_10.7 (solar) and Ap (geomagnetic) indices is highly correlated with the exospheric temperature, explaining ∼64% of the day-to-day variability. Furthermore, the exospheric temperature has good correlation with thermospheric parameters (e.g., neutral temperature, O₂ density, and NO emission index) sampled at various heights above ∼130 km, in spite of the well-known thermal gradient below ∼200 km. However, thermospheric temperature at altitudes around 100 km is not well correlated with the GOLD exospheric temperature. The result implies that effects other than thermospheric heating by solar Extreme Ultraviolet and geomagnetic activity take control below a threshold altitude that exists between ∼100 and ∼130 km.

Keywords: Aura/MLS; GOLD; ICON; Swarm; TIMED/SABER; exospheric temperature.