Nighttime Midlatitude E‐F Coupling in Geomagnetic Conjugate Ionospheres: A Double Thin Shell Model and a Multi‐Source Data Investigation

Abstract

Electrified ionosphere irregularities have extensively been an intriguing subject of research. In the summer hemisphere, at mid-latitudes during nighttime, electrified irregularities are ubiquitous in the F-region, manifested as wave-like electron density perturbations with horizontal wavelengths of several hundred kilometres and periods of 15-60 min (Bowman, 1985(Bowman, , 1990Hunsucker, 1982): typically known as medium-scale traveling ionospheric disturbances (MSTIDs). Recent studies have identified the characteristics of MSTIDs by using two-dimensional (2D) GPS-TEC (total electron content) maps (A. Saito, Fukao, & Miyazaki, 1998), three-dimensional (3-D) computerized ionospheric tomography technique (Ssessanga et al., 2015), and airglow imagers . One of the intriguing aspects of nighttime midlatitude MSTIDs is the northwest-southeast (NW-SE) (northeast-southwest; NE-SW) aligned frontal structures propagating toward equator-westward direction in the Northern (Southern) Hemisphere (Yokoyama, 2014). The Perkins instability could be the most likely mechanism to account for the directional preference of alignment and propagation of MSTID structures (Perkins, 1973). However, theoretical analysis have found that the growth rates of typical MSTIDs cannot be satisfied by a standalone Perkins instability, and have underscored a coupled effect from polarized Es structures (Es-layer instability) coupled to the Perkins instability (

Performance of the double-thin-shell approach for studying nighttime mediumscale traveling ionospheric disturbances using two dense GNSS observation networks in Japan

“…These GNSS stations receive signals from a variety of satellite navigation constellations, including GPS, GLONASS, Galileo, and BeiDou. Previously, the double-thin-shell approach relied only on GPS observations for modeling and analysis (Fu et al, 2022(Fu et al, , 2023. In this research, we explore the possibility and evaluate the performance of incorporating multi-GNSS observation data into the approach.…”

“…When multi-GNSS observation data are added, these numbers increase to approximately 20,000. In Fu et al (2022Fu et al ( , 2023, the original resolution of the double-thin-shell model was set to 2 minutes in time, 0.15 ∘ and 0.5 ∘ in longitude and latitude for E and F regions, respectively. To identify the solvable regions, the counts of IPPs in each cell of the E-and F-region shell heights were plotted in Figure 2(c-h) at the original resolution using the TEC observations at 09:00 UT (JST=UT+9 hours; Japan Standard Time), on day of year (DOY) 184, 2022.…”

“…It not only necessitates dense ray paths, but these rays also need to be welldistributed in space to provide more information on ionospheric disturbances. At the original resolution (0.15 ∘ and 0.5 ∘ in longitude and latitude for E and F regions, respectively, 2 min in time) used by Fu et al (2022Fu et al ( , 2023, the E-region reconstruction performance is limited and susceptible to the F-region disturbances when relying solely on GPS observations from GEONET. In response, increasing the density of GNSS stations and incorporating multi-GNSS observation data are expected to improve the reconstruction results by providing higher resolution and fidelity.…”