Global morphology and dynamic characteristics of ionospheric sporadic E layers based on COSMIC-2 observations

Sporadic E (Es) layers, transient thin structures (90–130 km) with enhanced electron density in the ionosphere, exert significant impacts on radio wave propagation. This study systematically unveils the global spatiotemporal distribution characteristics of Es layers using COSMIC-2 GNSS radio occultation (GNSS-RO) observations from 2022 to 2023. By integrating median and median absolute deviation (MAD) methodologies, we achieve a refined characterization of the altitude-latitude relationship in Es layer dynamics. The results reveal a day-to-night reversal in the geomagnetic latitudinal gradient of Es layer altitudes. During daytime, altitudes peak at mid-geomagnetic latitudes and are lowest near the geomagnetic equator, while at night, the highest altitudes occur near the equator and the lowest at mid-geomagnetic latitudes. Additionally, the analysis reveals fundamental hemispheric differences in diurnal altitude variations that are further modulated by seasonal effects. The semidiurnal characteristics of Es occurrence rates exist phase delays and increases central altitude with decreasing geomagnetic latitude. These findings may offer some insights into the processes involved in Es layer formation and evolution.