Coupling Between E Region Quasi‐Periodic Echoes and F Region Medium‐Scale Traveling Ionospheric Disturbances at Low Latitudes

Abstract

E region quasi-periodic (QP) echoes from a VHF coherent backscatter radar, sporadic E (E s ) layer from a digisonde, and F region medium-scale traveling ionospheric disturbances (MSTIDs) from global navigation satellite systems receivers were simultaneously observed at low latitudes. The results on the night of 3 March 2018 show that the QP echoes in radar height-time intensity maps were clustered into groups, coinciding with the periods of MSTIDs and strong E s layer. The MSTIDs had phase fronts elongating in the northwest-southeast direction and propagated southwestward from middle to low latitudes. Similar to the propagation direction of MSTIDs, the low-latitude E s layers also propagated southwestward. For the QP echoing clusters, a westward drift was seen from the radar multibeam observations. The Doppler velocities of QP echoes show beam dependence, with significantly enhanced positive values (motion away from the radar) in the westernmost beam. Based on a preliminary statistical analysis during the period March-June 2018, it was found that out of a total of 102 nights, there are 32 nights when QP echoes were generated. The simultaneous occurrences of QP echoes and MSTIDs were observed on six nights. We suggest that when the MSTIDs coming from middle latitudes approach low latitudes, the polarization electric fields associated with the MSTIDs could modulate the E region plasma instability producing QP echoes at low latitudes through the E-F region electrodynamic coupling.

Simultaneous Observations of a Polar Cap Sporadic‐E Layer by Twin Incoherent Scatter Radars at Resolute

“…Note that the full appearance of the polar cap Es layer is recorded by CADI rather than the twin radars due to the lower density of polar cap Es layer during these gaps possibly attenuated by some functions. Furthermore, we also discover a new phenomenon of double Es layers at divided altitudes over the polar cap region, which has been reported at low latitude region from Digisonde and Very High Frequency radar (e.g., Xie et al., 2020 and references therein). However, it should be pointed out that the double Es layers have not been captured by the ionograms of Resolute CADI co‐located with the twin ISR radars.…”

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

“…Tsunoda and Cosgrove (2001) found that with a positive feedback mechanism under a E-F coupling process, the growth rates were larger than in both independent mechanisms. Different numerical simulations (Cosgrove 2007;Yokoyama et al 2009), and joint observational experiments (Haldoupis et al 2003;Otsuka et al 2007;Saito et al 2007;Narayanan et al 2018;Zhou et al 2018;Liu et al 2019Liu et al , 2020Xie et al 2020) followed, and confirmed a number of parameters associated with a coupled E-F ionosphere in the night-time midlatitudes. Even with such rich literature, different perspectives still exist regarding the causal relationship in the E-F coupling (Hysell et al 2018).…”

“…Since the mid-latitude field-aligned irregularity (FAI) in E region is considered associated with the horizontal inhomogeneity of an Es layer (Larsen 2000;Maruyama et al 2006), the structured coherent backscatter radar echoes, so-called quasi-periodic (QP) echoes, are associated with Es layers and usually used to indicate the Es dynamics and morphology (Yamamoto et al 1994;Maruyama et al 2000;Saito et al 2007;Xie et al 2020). MUR, located at 34.9 • N, 136.1 • E, Shigaraki, Japan, has been used for detecting backscatter echoes from plasma irregularities in both E region (Yamamoto et al 1994) and F region (Saito et al 2002).…”

IONISE: An Ionospheric Observational Network for Irregularity and Scintillation in East and Southeast Asia

“…It was found that the horizontal elongation pattern and drift of E s structures resemble those of TIDs. The similarities between the two phenomena in different altitude regions indicate some coupling process between different layers of the ionosphere (e.g., Otsuka et al, 2008; Xie et al, 2020).…”