High‐Resolution 3‐D Imaging of Daytime Sporadic‐E Over Japan by Using GNSS TEC and Ionosondes

Abstract

Sporadic-E (E s ) are electron density inhomogeneities manifested in the ionospheric E region. At midlatitude area, during the daytime, E s is suggested to occur due to reinforced metallic (of meteoric origin) ionization in altitude range ∼95-120 km (Whitehead, 1989). Occasionally, E s becomes denser than the normal E-and F-layer densities, exhibiting a high correlation of occurrence with intense transionospheric signal scintillation (Maeda & Heki, 2014). Consequently, to forecast and draw patterns in the scintillation morphology, the space weather community has extensively investigated the E s structure both theoretically and experimentally. For example, information on the horizontal structures of midlatitude E s has been inferred by using ionosondes (Whitehead, 1972), radars (Miller & Smith, 1975), and rockets (Yamamoto et al., 1998. More so, S. Saito et al. ( 2006) obtained three-dimensional (3-D) structures of E s patches by using the middle and upper atmosphere (MU) radar at Shigaraki, Japan. Wu et al. (2005) deduced occurrence rates and intensities of E s at summertime midlatitudes, by using radio occultation measurements around the globe. Haldoupis (2011) and references therein have discussed an excellent tutorial review that summarizes the results from most of these studies and their affirmation on the E s structure. The literature suggests that the occurrence of E s varies with local time, altitude, latitude, longitude, and seasons, and its existence depends on the tidal wind, the Earth's geomagnetic field, and the level of meteoric depositions (Whitehead, 1989). Even with such rich literature, the E s generating mechanisms are not fully understood, although the wind shear theory driven by zonal winds has widely been accepted for the E s

On using a double-thin-shell approach and TEC perturbation component to sound night-time mid-latitude E–F coupling

“…Based on the simulation results in section "Simulation", to reduce the ambiguity of the structures in E shell, reconstructions with IE/IF < 0.3 were excluded. Furthermore, from the work of Fu et al (2021) that utilized the same geometry, it is better to focus on the region bounded by yellow dashed lines in Fig. 4: most data points are bound to this region.…”

“…Before analyzing the E-F coupling data set, we addressed two questions to raise confidence in the proposed double-thin-shell model technique: (1) Is the technique able to reconstruct or place the perturbations at the appropriate shell? With disregard to the difference in night and day ionosphere density concentrations, here, as a test case, we analyzed a carefully selected daytime Es event on 21 May 2010 (day of the year (DOY) 141), previously analyzed by Maeda and Heki (2014) and Fu et al (2021) when the F-region was deemed quiet. The reasoning was that at daytime a well-developed and highly (9)…”

“…conducting E region limits polarization electric fields that could facilitate the E-F coupling (Kelley, 2009;Fu et al 2021). Therefore, the signal should be from the E shell, and the F-shell noise dominated.…”

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

“…Es (sporadic E) are thin layers of metallic ion plasma that predominantly form at altitudes of 95–125 km in the ionospheric E region (Whitehead, 1989). Occasionally, the Es layer anomalously exhibits greater plasma densities than the F region; an occurrence that highly correlates with intense trans‐ionospheric signal scintillation (Fu, Ssessanga, et al., 2021). For Es layers at midlatitudes, neutral wind shear theory has been widely accepted for the generation mechanism (Haldoupis, 2012; Mathews, 1998), and the pronounced seasonal dependence is attributed to the tidal wind, the Earth's geomagnetic field, and the level of meteoric depositions (Haldoupis et al., 2007; Whitehead, 1989).…”

Controlling Factors of Artificial Irregularities Triggered by Chemical Release at Low Latitude Ionosphere

“…Variation of the total electron content (TEC) along raypath of the satellite‐to‐ground was usually described as the rate of change of TEC index (Amabayo et al., 2015; Fu et al., 2021; Luo et al., 2022). It is believed that the formation of density irregularities and occurrence of ionospheric scintillation is highly consistent with the ROTI value (Nishioka et al., 2008).…”