Variations in Thermosphere Composition and Ionosphere Total Electron Content Under “Geomagnetically Quiet” Conditions at Solar‐Minimum

• Published in: Geophysical research letters 2021-06, Vol.48 (11), p.n/a
• Main Authors: Cai, Xuguang, Burns, Alan G., Wang, Wenbin, Qian, Liying, Pedatella, Nicholas, Coster, Anthea, Zhang, Shunrong, Solomon, Stanley C., Eastes, Richard W., Daniell, Robert E., McClintock, William E.
• Format: Article
• Language: English
• Subjects: geomagnetic activity; O/N2 column density ratio; thermosphere composition; total electron content
• ISSN: 0094-8276; 1944-8007
• DOI: 10.1029/2021GL093300

We conducted observational and modeling studies of thermospheric composition and ionospheric total electron content (TEC) variations during two geomagnetically quiet periods (maximum Kp = 1.7) at solar minimum. Daytime thermospheric O and N2 column density ratio (∑O/N2) observed by Global‐scale Observations of the Limb and Disk and TEC from a network of ground‐based Global Navigation Satellites System receivers both exhibited large (∼30% of reference values) and long‐lived (5–11 h) day‐to‐day variations in roughly the same mid‐latitude geographic regions. Numerical simulations replicated the observed variability, though not perfectly. Analysis of the simulations suggested that the variations were mainly generated in the high‐latitudes and were subsequently advected equatorward and westward. When high‐latitudes input was turned off in simulations, the variations were negligible. This suggested the potentially important role of high‐latitude geomagnetic forcing in thermospheric composition and ionospheric density variations at mid‐latitudes even during some “geomagnetically quiet” periods at solar‐minimum. Plain Language Summary This study presents two cases when geomagnetic forcing can be a plausible source of mid‐latitude thermospheric composition and ionosphere density variations even during what is typically considered as geomagnetically quiet times (magnetic activity index Kp