New Findings of the Sporadic E (Es) Layer Development Around the Magnetic Equator During a High‐Speed Solar (HSS) Wind Stream Event

Abstract

The equatorial (Esq) and blanketing (Esb) sporadic (Es) layers occur due to the Equatorial Electrojet Current (EEJ) plasma instabilities and tidal wind components, respectively. Both Esq and Esb layers can appear concurrently over some Brazilian equatorial regions due to the peculiar geomagnetic field configuration in this sector. Previous works indicate that the inclination angle limit for the Esq occurrence in ionograms is 7°. However, we found evidence that regions more distant can also experience such equatorial dynamics during disturbed periods. In this context, we deeply investigated this EEJ influence expansion effect by analyzing the Esq layers in regions not so close to the magnetic equator during a high‐speed solar wind stream event that occurred on May 05 and 06, 2018. To explain these atypical Esq layer occurrences, we considered the Es layer parameters obtained from digital ionosondes over the Brazilian regions, São Luís (dip: 9.5°), and Araguatins (dip: 10.5°). We use magnetometer data and a model named MIRE (E Region Ionospheric Model) to validate this mechanism. The results show that the eastward electric field of the Gradient Drift instability in the EEJ is effective during the magnetic storm main phase in the boundary equatorial magnetic sites, creating the Esq layers. Thus, the EEJ plasma irregularity superimposes the wind shear mechanism, changing the Es layer dynamics during disturbed periods over the magnetic equator boundary sites. Therefore, this work establishes new findings of the EEJ influence expansion dynamics in the Es layer formation over the Brazilian regions, which was considered in MIRE for the first time.

An Empirical Model of the Ionospheric Sporadic E Layer Based on GNSS Radio Occultation Data

“…Besides, the influences of solar activity, equatorial electrojet current plasma instabilities, and geomagnetic disturbances are not yet included in the model. The short‐term variations in the low‐ and high‐latitude E s layers are associated with fast solar wind streams (Davies, 1990; L. Resende et al., 2021) and recurrent geomagnetic activity (Yu, Scott, Xue, Yue, Chi, et al., 2021).…”

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).…”

“…(2021) and Resende, Zhu, et al. (2021) also used the GSWM‐00 for providing the winds profiles as input in MIRE to simulate the Es layer dynamics in the Brazilian territory. A complete mathematical description of MIRE can be found in Carrasco et al.…”

E‐Field Effects on Day‐To‐Day Variations of Geomagnetic Mid‐Latitude Sporadic E Layers

“…The EsLs are called the blanketing EsLs and affected by both E‐fields and winds (Moro et al., 2017; Resende et al., 2016, 2018). At geomagnetic low‐latitudes, disturbance dynamo E‐field effects on EsL dynamics have been investigated recently (e.g., Resende et al., 2020; Resende, Shi, et al., 2021; Resende, Zhu, et al., 2021). Moreover, it is known that equatorial E‐fields due to the evening prereversal enhancement can cause low‐latitude EsL disruption or intensification (e.g., Abdu et al., 2003; Carrasco et al., 2007).…”