Document Type
Article
Publication Date
4-26-2025
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 reaching up to ~30 km compared to IRI-2020 and ~45 km compared to NeQuick-2. As models face challenges due to lack of reliable measurements, especially in the topside and bottomside, improvements in GNSS-LEO observing techniques can provide more accurate and comprehensive data to characterize the global ionosphere.
Source Publication
JGR Space Physics (ISSN 2169-9380 | eISSN 2169-9402)
Recommended Citation
Swarnalingam, N., Wu, D. L., Bilitza, D., Emmons, D. J., Salinas, C. C. J. H., Smirnov, A., & Migoya-Orue, Y. (2025). Global ionospheric F region parameters from GNSS-POD limb measurements: Evaluations and comparisons with two empirical models - IRI-2020 and NeQuick-2. Journal of Geophysical Research: Space Physics, 130, e2024JA033466. https://doi.org/10.1029/2024JA033466
Comments
© 2025. American Geophysical Union. All Rights Reserved.
This article is shared on AFIT Scholar as the institutional repository of the employer of co-author Daniel Emmons. The AGU publications policy embargo for versions of record was observed for this posting.
Funding notes for this article:
NASA Headquarters. Grant Numbers: 936723.02.01.12.48, 880292.04.02.01.68
NASA's Living With a Star and Commercial Smallsat Data Acquisition. Grant Numbers: 936723.02.01.12.48, 880292.04.02.01.68