Abstract
Abstract. The occurrence of sporadic E (Es) layers has been a hot scientific topic for a long time. The GNSS (global navigation satellite system)-based radio occultation (RO) has proven to be a powerful technique for detecting the global Es layers. In this paper, we focus on some cases of complex Es layers based on the RO data from multiple missions processed in UCAR/CDAAC (University Corporation for Atmospheric Research (UCAR) the Constellation Observing System for Meteorology, Ionosphere, and Climate (COSMIC) Data Analysis and Archive Center (CDAAC)). We first show some examples of multiple Es layers occurred in one RO event. Based on the evaluations between colocated simultaneous RO events and between RO and lidar observations, it could be concluded that some of these do manifest the multiple Es layer structures. We then show a case of the occurrence of Es in a broad region during a certain time interval. The result is then validated by independent ionosondes observations. It is possible to explain these complex Es structures using the popular wind shear theory. We could map the global Es occurrence routinely in the near future, given that more RO data will be available. Further statistical studies will enhance our understanding of the Es mechanism. The understanding of Es should benefit both Es-based long-distance communication and accurate neutral RO retrievals.
Highlights
The ionospheric E region is ∼ 90–120 km above the Earth’s surface
2.2 Evaluation by colocated simultaneous radio occultation (RO) events In University Corporation for Atmospheric Research (UCAR)/COSMIC Data Analysis and Archive Center (CDAAC), we process most RO data available to the scientific community (Schreiner et al, 2011). This comes from missions including COSMIC, CHAMP, GRACE, SACC, TerraSAR-X, C/NOFS, and MetopA/B
Xue et al (2013) reported an example showing that the lidar observes thermosphere enhanced sodium layers (TeSLs) associated with simultaneous double peaks of signal-to-noise ratio (SNR) made by colocated RO events from TerraSAR-X
Summary
The ionospheric E region is ∼ 90–120 km above the Earth’s surface. Its electrons mainly originate from soft X-ray and far ultraviolet (UV) solar radiation ionization of the neutral atmosphere. The understanding of the E region could contribute to the studies related to electrojets of highlatitude and equatorial regions, ionospheric instabilities, and ionosphere–thermosphere–magnetosphere couplings. A thin layer of enhanced ionization appears in the E region, which is called the sporadic E layer (Es). The occurrence of Es is controlled by multiple factors, including tidal wind, the Earth’s geomagnetic field, and meteoric deposition of metallic material in the background thermosphere. These factors result in variations of Es occurrence with respect to local time, altitude, latitude, longitude, and season (Haldoupis, 2011). Please note that the term Es is widely used to represent the inhomogeneity of the ionospheric E layer
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