Occurrences of Regional Strong E_s Irregularities and Corresponding Scintillations Characterized Using a High‐Temporal‐Resolution GNSS Network

Abstract

Strong sporadic E (Es) irregularities over China are investigated based on high‐temporal‐resolution total electron content (TEC) derived from two crossed chains of Beidou geostationary satellite (BD‐GEO) TEC receivers along 110°E and 23°N, respectively. The high resolution rate of TEC index (HR‐ROTI) calculated at an interval of 30 s, is proposed to characterize small‐scale strong Es irregularity structures. Based on the HR‐ROTI measurements and the typical drift velocity of Es 60 m/s, the scale sizes of strong Es irregularity structures were revealed to be mainly ∼7 km. The structures were mostly quasi‐periodically separated with distances of 7–16 km. Through a further statistical analysis of strong Es irregularity structures along the two chains, it was found that the Es irregularity structures predominantly occur during local summer at middle and low latitudes, with the occurrence rate peaking at ∼30°N. On average approximately 2–5 small‐scale strong Es irregularity structures may be embedded in one larger‐scale structure. Unlike the equatorial and low‐latitude F‐region irregularities which cause scintillations under most conditions, the strong Es irregularity characterized by HR‐ROTI caused scintillation with relatively low occurrence rates of 37% and 12% at middle and low latitudes, respectively.

Comparison of Seasonal foEs and fbEs Occurrence Rates Derived from Global Digisonde Measurements

“…Kelvin-Helmholtz instabilities [44] can modulate E s layers to form billowy, small-scale structures [26,27,45] that affect both the spatial profiles and ionosonde measurements of the layers. This supports previous global [5,37,38] and regional [28] occurrence rate studies with large variations over relatively short distances. A simple trend as a function of geographic longitude is difficult to extract because of the strong dependence on geomagnetic latitude; however, the variation between regions with similar latitudes indicates a complex formation dependence on additional factors not included in the simple wind shear theory.…”

“…In addition to ionosondes, sporadic-E can be measured from other instruments, such as incoherent scatter radars (ISRs) [25], ground-based global navigation satellite system (GNSS) measurements [26][27][28], and GPS radio occultation (RO) [29,30]. ISR measurements provide the most detailed observations of E s characteristics and structure [13,31,32], but the limited number of sites across the globe and measurement cadence are lacking for global climatological studies.…”

“…ISR measurements provide the most detailed observations of E s characteristics and structure [13,31,32], but the limited number of sites across the globe and measurement cadence are lacking for global climatological studies. Ground-based GNSS measurements allow for unprecedented largescale studies of E s morphology for strong layers (foEs > 14 MHz) over areas with GNSS networks, such as Japan [26] and China [27,28]. These ground-based measurements provide detailed information on the elongation, orientation, scale-size, and horizontal motion of the layers in addition to regional occurrence rates for exceptionally strong E s layers.…”

On the Spatial Structure and Zonal Drift of Low Latitude E Region Irregularity Patches Over Hainan

“…The result shows that ∼67% daytime E region FAIs were accompanied by considerable (>0.1 TECU/min) HR-ROTI structures (18 out of 27 daytime cases). Further, we employed the same method as in Sun et al (2021a) to investigate the separations between the small-scale strong E s structures characterized by HR-ROTI spikes. In brief, we first measured the intervals between the HR-ROTI spikes to derive the temporal separation between strong E s structures.…”

“…Further, we employed the same method as in Sun et al. (2021a) to investigate the separations between the small‐scale strong E s structures characterized by HR‐ROTI spikes. In brief, we first measured the intervals between the HR‐ROTI spikes to derive the temporal separation between strong E s structures.…”