Difference in the Sporadic E Layer Occurrence Ratio Between the Southern and Northern Low Magnetic Latitude Regions as Observed by COSMIC Radio Occultation Data

Abstract

In this paper, the difference in the sporadic E layer occurrence ratio between two low-magneticlatitude (±5°-±15°) regions is analyzed by using COSMIC scintillation observations covering the period from 2007.001-2017.365. Obvious longitudinal, seasonal and LT dependencies of this phenomenon are found. Most features of the differences between two hemispheres could be explained by the difference in zonal vertical wind shear between the two hemispheres induced by the difference between the magnetic and geographic latitudes of the studied regions. This result also indicates that the wind shear mechanism still dominates sporadic E layer formation in lowmagnetic-latitude regions.

Global Temporal and Spatial Variations of Ionospheric Sporadic‐E Derived From Radio Occultation Measurements

“…These regions of lower occurrence have previously been explained likely to be due to the geomagnetic field lines being more vertically aligned in those areas (Arras et al., 2008). All these features in Es spatial distribution confirm observations in previous studies (Chu et al., 2014; Niu, 2021; Wu et al., 2005).…”

“…With that, they discovered features in spatial distribution such as the longitudinal Es distribution follows the structure of the magnetic equator but with almost no Es occurrence at the magnetic equator itself, and an occurrence depression was observed over the South‐Africa region. Today, these observed Es dependencies on seasons and local time along with the spatial distribution are generally acknowledged, as they have been confirmed by many studies (Arras & Wickert, 2018; Chu et al., 2014; Niu, 2021; Wu, 2020).…”

“…Various methods have been used to study the ionospheric E‐layer using COSMIC‐1 data (Arras & Wickert, 2018; Chu et al., 2014; Gooch et al., 2020; Niu, 2021; Yu et al., 2020). Many of them incorporate the commonly used S 4 amplitude scintillation index to some degree as well as phase scintillations.…”

“…The Es dependence on solar activity has also been investigated in a number of articles, both using RO data and stationary ionosonde measurements. In a study on Es at low magnetic latitudes (5°–15°) that used COSMIC‐1 data from the years 2007–2017 (Niu, 2021), no obvious dependence on solar activity was found. In that article, the author stated that it was in agreement with previous results, and as an example pointed to research that used ionosonde data to observe Es, where in the data from a station situated in Rome (41.8°N, 12.5°E) for the years 1976–2007, no significant dependence on solar activity was found (Pietrella & Bianchi, 2009).…”

Deriving Ionospheric Sporadic E Intensity From FORMOSAT‐3/COSMIC and FY‐3C Radio Occultation Measurements

“…(2020) and should be attributed to the effect of the geomagnetic field and its high horizontal intensity and inclination in polar regions. Es intensity along the geomagnetic equator is significantly lower than that on both sides, forming a rift‐like band, which is due to that the inclination of geomagnetic field near the geomagnetic equator is close to 0° and prevents metal ions from convergence (Brahmanandam et al., 2012; Chu et al., 2014; Luo et al., 2021; Niu, 2021; Yamazaki et al., 2022). In the North America (30°–50°N and 80°–120°W) and the South Atlantic Anomaly (SAA) zone (30°–60°S and 40°W–20°E) exist the Es layers weaker than those in other regions of the same latitudes.…”