Quarterdiurnal signature in sporadic E occurrence rates and comparison with neutral wind shear

Abstract

Abstract. The GPS radio occultation (RO) technique is used to study sporadic E (ES) layer plasma irregularities of the Earth’s ionosphere on a global scale using GPS signal-to-noise ratio (SNR) profiles from the COSMIC/FORMOSAT-3 satellite. The maximum deviation from the mean SNR can be attributed to the height of the ES layer. ES are generally accepted to be produced by ion convergence due to vertical wind shear in the presence of a horizontal component of the Earth magnetic field, while the wind shear is provided mainly by solar tides. Here we present analyses of quarterdiurnal (QDT) signatures in ES occurrence rates. We find from a local comparison with mesosphere/lower thermosphere wind shear obtained with a meteor radar at Collm (51:3°N, 13:0°E), that the phases of the QDT in ES agree well with those of negative wind shear for all seasons except for summer, when the QDT amplitudes are small. We also compare the global QDT ES signal with numerical model results. The global distribution of ES occurrence rates qualitatively agrees with the modeled zonal wind shears. The results indicate that zonal wind shear is indeed an important driving mechanism for the QDT seen in ES.

Altitudinal and Latitudinal Variations in Ionospheric Sporadic‐E Layer Obtained From FORMOSAT‐3/COSMIC Radio Occultation

“…Besides, as the latitude changes from mid-latitude to low-latitude, the height of EsOR gradually decreases from above 100 km to below 100 km (Figure 3). This result supports the previous views of Jacobi et al (2019) and Qiu et al (2021) and can be attributed to the altitude-latitude distribution of wind shear (Figure S4) controlled by the atmospheric tides (Liu et al, 2019a;Qiu et al, 2021).…”

“…This result supports the previous views of Jacobi et al. (2019) and Qiu et al. (2021) and can be attributed to the altitude‐latitude distribution of wind shear (Figure ) controlled by the atmospheric tides (Liu et al., 2019a; Qiu et al., 2021).…”

“…On the other hand, the altitude‐latitude distribution of the EsOR shows that the Es layer frequently appears at about 90–120 km altitude at middle latitudes (Arras et al., 2008). An interesting point is that the Es layers are easier to be recorded at altitudes below 100 km for low latitudes, but above 100 km for middle latitudes (Jacobi et al., 2019). Qiu et al.…”

“…10.1029/2021JA029454 2 of 13 but above 100 km for middle latitudes (Jacobi et al, 2019). Qiu et al (2021) also used the four Chinese ionosondes to analyze the dynamic descent of the Es traces and found that Es layers over Sanya at low latitudes are easier to descend to lower altitudes below 100 km compared to the other three stations.…”

Relationship Between Wavenumber 4 Pattern of Sporadic E Layer Intensity and Eastward Propagating Diurnal Tide With Zonal Wavenumber 3 in Low Latitude Region

“…found in the upper E region (above 110 km) in the low latitude region by using the Arecibo ISR observations (Morton et al, 1993;Tong et al, 1988). Recently, Jacobi et al (2019) also reported a 6-h periodicity, which shows good agreement between phases of the 6-h periodicity in sporadic E and the negative vertical shear of the zonal wind for all seasons except for summer in the mid-latitude region at Collm (51.3°N, 13.0°E). In recent years, observations obtained from radio occultation (RO) systems have been widely used in the detection and analysis of sporadic E layers.…”