Drivers of Mid‐Latitude Quiet‐Time Longitude Variations in Ionospheric Density

Abstract The aim of this study is to provide an observational benchmark of mid‐latitude quiet‐time variability in winds, O/N 2 , and TEC across longitude and local time to provide a foundation for future model–data comparison studies. The quiet‐time ionospheric structure is not uniform but rather exhibits pronounced longitudinal and local‐time variability. This study analyzes quiet‐time and mid‐latitude total electron content (TEC) behavior as a function of season, longitude, and local time with regard to three potential drivers: neutral winds, composition (O/N 2 ), and wind‐induced vertical motion. Using an observational systems approach, we jointly analyze mid‐latitude total electron content (TEC) together with thermospheric winds and composition (O/N 2 ) from four instruments on three satellites during quiet periods (low F10.7, low Ap, nominal polar‐vortex state) in 2020. The results reveal the following: (a) neutral winds exhibit strong diurnal and seasonal variation, with notable longitudinal asymmetries that influence latitudinal advection of neutral constituents, (b) O/N 2 displays clear seasonal structure and significant longitudinal variability, some may be driven by winds and some may be driven by wave‐driven processes, and (c) The plasma motion, determined by the interaction between neutral winds and the geomagnetic field, explains many features of TEC variability, that is, not captured by composition or winds alone.