Occurrence and Modeling Examination of Sporadic‐E Layers in the Region of the South America (Atlantic) Magnetic Anomaly

Abstract

In this work, the occurrence of different types of sporadic-E layers (Es) was described for two stations located in the region of the South America Magnetic Anomaly: Jataí and São José dos Campos. The results show the hourly and monthly values of the Es occurrences and presented five types of layers (cusp, high, flat, low, and slant), with the flat/low types (Es f/l ) being the most frequent over both stations. We also analyzed the Es layer parameters of blanketing frequency (f b Es) and top frequency (f t Es) obtained from ionosonde data during storm-time periods, in order to investigate possible evidences of energetic particle-induced E-layer ionization. The results revealed increases in the values of the nighttime f t Es and f b Es, which can be related to the particle precipitation in the South America Magnetic Anomaly region. Additionally, we investigated the roles of the wind shear mechanism in the formation of the Es types by using a modified form of the Ionospheric E-Region Model (MIRE), which incorporates tidal winds obtained from meteor radar data. Furthermore, the electron densities deduced from f b Es parameter were compared with the maximum electron densities obtained from MIRE simulations. Depending on local time and season, the initial results revealed for both stations some discrepancies between modeled and measured electron densities. However, a better fitting was obtained when the amplitudes of the zonal/meridional wind components were adjusted by some factor, which may be attributed to the possible effects of day-to-day tidal wind variability and their interaction with gravity and planetary waves.Key Points:• The flat/low Es are the most frequent types of sporadic layers observed at the low-latitude stations • Es frequency parameters during moderate storms showed evidences of energetic particle-induced E-layer ionization around the SAMA region • Modeled and measured electron densities revealed the role of the wind shear mechanism in the formation of the observed Es layers

Different Sporadic‐E (Es) Layer Types Development During the August 2018 Geomagnetic Storm: Evidence of Auroral Type (Esa) Over the SAMA Region

“…The Es layer descends to around 100 km from 4:00 UT to 8:00 UT, which is a typical movement due to the semidiurnal (period of 12 hr) and diurnal (period of 24 hr) tides behavior as explained by Mathews (1998). The MIRE was able to simulate the Es b layers at low latitudes in several studies (Conceição‐Santos et al., 2019, 2020; Moro et al., 2017; Resende et al., 2017a, 2017b, 2020; Resende, Shi, et al., 2021; Resende, Zhu, et al., 2021).…”

“…An effort was carried out by Conceição‐Santos et al. (2019) to investigate the possible evidence of energetic particle precipitation over two low‐latitude stations in Brazil, Jataí (17.9°S, 51.7°W, dip: −13.4°) and São José dos Campos (23.2°S, 45.8°W, dip: −21°), in 2016. The authors observed increases in ft Es and fb Es, affirming evidence of particle precipitation over the stations.…”

“…However, it would be important to study if such Es a layers appear in west stations of Cachoeira Paulista since the SAMA continues to grow and weaken as it moves to the west direction (Finlay et al, 2020). An effort was carried out by Conceição-Santos et al (2019) to investigate the possible evidence of energetic particle precipitation over two low-latitude stations in Brazil, Jataí (17.9°S, 51.7°W, dip: −13.4°) and São José dos Campos (23.2°S,45.8°W,, in 2016. The authors observed increases in ftEs and fbEs, affirming evidence of particle precipitation over the stations.…”

Effects of the terdiurnal tide on the Sporadic-E layers (Es) development at low latitudes over the Brazilian sector

“…The extended version of the E Region Ionospheric Model (MIRE) was used in this study to calculate the Es layers' electronic density profile (Resende et al, 2017a;Conceição-Santos et al, 2019). The MIRE uses the continuity equation to calculate the sum of the ionic density for the main constituents, such as 𝑁𝑂 + , 𝑂 2 + , 𝑂 Equation 1.…”

“…The MIRE uses the continuity equation to calculate the sum of the ionic density for the main constituents, such as 𝑁𝑂 + , 𝑂 2 + , 𝑂 Equation 1. The simulations are obtained in a space-time of approximately 0.2 km height every 2 minutes between 00-24 UT for altitudes between 86 and 140 km, assuming photochemical equilibrium of the species as initial conditions for the numerical equations to be solved until ion convergence is reached (Carrasco et al, 2007;Resende et al, 2016;2017a;2017b;Conceição-Santos et al, 2019;2020).…”