Analysis of the different physical mechanisms in the atypical sporadic E (Es) layer occurrence over a low latitude region in the Brazilian sector

Abstract

We present a study about the atypical and spreading Sporadic E-layers (Es) observed in Digisonde data. We analyzed a set of days around space weather events from 2016 to 2018 over Cachoeira Paulista (CXP, 22.41°S, 45°W, dip ∼35°), a low-latitude Brazilian station. The inhomogeneous Es layer is associated with the auroral-type Es layer (Esa) occurrence in this region due to the presence of South American Magnetic Anomaly (SAMA). However, we also observe that the spreading Es layers occurred days before the magnetic storms or quiet times. Also, this specific type of Es layer has some different characteristics concerning the Esa layer. We used data from the imager, satellite, and meteor radar to understand the dynamic processes acting in this Es layer formation. Our results lead us to believe that other mechanisms affect the Es layer development. We show evidence that the instabilities added to the wind shear mechanism can cause the atypical Es layers, such as Kelvin-Helmholtz instability (KHI). Finally, an important discovery of this work is that the spreading Es layer, mainly during quiet times, is not necessarily due to the particle precipitation due to the SAMA. We found that the wind shear can be turbulent, influencing the Es layer development. Lastly, our analysis better understood the Es layer behavior during quiet and disturbed times.

Wind Shear Driven Double Layer Structures of E‐Region Irregularities at Low Latitudes

“…The results indicate that the generation of the structures at the two layers could be under the same driving force, that is, GWs. Besides, according to previous studies, the slant Es trace in ionograms (e.g., 12:00 UT in Figure 2a) and the wavelike manifestation of the irregularity structure (e.g., 12:11 UT in Figure 1i) may indicate the possible presence of GWs (e.g., Resende et al, 2023;Sun, Li, Han, et al, 2023). Therefore, comparing with K-H instability, GWs were more likely to provide simultaneous modulation on the two separated FAI layers in the present study.…”

Analysis of Blanketing Sporadic‐E Layer and Associated Tidal Periodicities Over a Brazilian Station Undergoing a Transition From Low Latitude to Midlatitude

“…One is the type “s” (Es s , slant) attributed to the gravity waves in the mesosphere and lower thermosphere (MLT; Cohen et al., 1962). The other one is related to spread Es traces that can be attributed to energetic particle precipitation during geomagnetic storms (Da Silva et al., 2022; Moro, Xu, Denardini, Resende, et al., 2022) or the presence of very turbulent wind flows (Resende et al., 2023). These additional types are labeled as “Others” and represented by the yellow bar in the figure.…”