Global Ionospheric F Region Parameters From GNSS‐POD Limb Measurements: Evaluations and Comparisons With Two Empirical Models ‐ IRI‐2020 and NeQuick‐2

作者：Nimalan Swarnalingam, Dong L. Wu, D. Bilitza, Daniel J. Emmons, Cornelius Csar Jude H. Salinas, Artem Smirnov, Yenca Migoya‐Orué · 发表于：Journal of Geophysical Research Space Physics · 年份：2025 · DOI：10.1029/2024ja033466 · 被引用次数：7 · 研究领域：Ionosphere and magnetosphere dynamics、GNSS positioning and interference、Geophysics and Gravity Measurements

Abstract An optimal estimation (OE) technique has recently been developed for F region electron density (Ne) using Global Navigation Satellite System (GNSS) limb sounding on low Earth orbit (LEO) satellites (COSMIC‐2, Spire, and FengYun‐3). This method provides unprecedented spatiotemporal sampling for global monthly Ne climatology within 100–500 km in 2 hr intervals. The global dataset, collected during mid to moderately high solar activity, is compared with leading models: IRI‐2020 and NeQuick‐2. Diurnal variations in summer, winter, and equinoctial months are examined for the F2‐layer peak, as well as the topside and bottomside of the F region. The observed and modeled NmF2 and hmF2 show good agreement during the daytime, but discrepancies appear with NeQuick‐2 at night. The OE‐retrieved dataset reveals distinct interhemispheric differences in topside scale height between the summer and winter hemispheres, which are not adequately captured by models. The estimated topside scale heights in IRI‐2020 are 20–30 km higher than observations on regional scale, but this difference decreases to 12–20 km on global scale. In the bottomside, the agreement between observations and models varies significantly between daytime and nighttime conditions. During the daytime, the global bottomside thicknesses derived from OE‐retrieved profiles agree within 10 km with the IRI‐2020, but they are 10–15 km higher than NeQuick‐2. The nighttime thicknesses differ substantially, with deviations reac...