Equatorial E Region Electric Fields and Sporadic E Layer Responses to the Recovery Phase of the November 2004 Geomagnetic Storm

Abstract

Equatorial E region electric fields (EEFs) inferred from coherent radar data, sporadic‐E (Es) layers observed from a digital ionosonde data, and modeling results are used to study the responses of the equatorial E region over São Luís (SLZ, 2.3°S, 44.2°W, ~−7° dip angle), Brazil, during the super storm of November 2004. The EEF is presented in terms of the zonal (Ey) and vertical (Ez) components in order to analyze the corresponding characteristics of different types of Es seen in ionograms and simulated with the E region ionospheric model. We bring out the variabilities of Ey and Ez components with storm time changes in the equatorial E region. In addition, some aspects of the electric fields and Es behavior in three cases of weak, very weak, and strong Type II occurrences during the recovery phase of the geomagnetic storm are discussed. The connection between the enhanced occurrence and suppressions of the Type II irregularities and the q‐type Es (Esq) controlled by electric fields, with the development or disruption of the blanketing sporadic E (Esb) layers produced by wind shear mechanism, is also presented. The mutual presence of Esq along with the Esb occurrences is a clear indicator of the secular drift of the magnetic equator and hence that of the equatorial electrojet (EEJ) over SLZ. The results show evidence about the EEJ and Es layer electrodynamics and coupling during geomagnetic disturbance time electric fields.

The Influence of Disturbance Dynamo Electric Field in the Formation of Strong Sporadic E Layers Over Boa Vista, a Low‐Latitude Station in the American Sector

“…In the previous studies that used MIRE (Moro et al, 2017;Resende et al, 2016;Resende et al, 2017a;Resende et al, 2017b), the authors fitted the wind model from the amplitude, wavelength, and phase parameters computed using the observational data of the meteor radars installed in Brazilian low-latitude regions. However, there is no meteor radar available near BV.…”

“…Therefore, the constant westward electric field strengthened the Es layers in BV. Resende et al (2016) and Moro et al (2017) showed that the zonal electric field can cause a modulation in the existing Es layers because of the tidal wind mechanism. They studied the equatorial region electric field created by the EEJ current to analyze the Es layer formation, concluding that the zonal electric fields are not efficient enough to create or disrupt the Es layers.…”

“…Although these layers are named sporadic, they can be considered as permanent layers due to their frequent observation and the long lifetime of the metallic ions, such as Fe + , Mg + , K + , Ca + , and Na + (Kopp, 1997). Several authors studied the Es layer characteristics showing that their intensity and locations are controlled generally by the tidal wind atmospheric dynamics (Pignalberi et al, 2014;Prasad et al, 2012;Resende et al, 2017a) and, in some cases, by the electric field (Abdu et al, 2014;Moro et al, 2017;Resende et al, 2017b).…”

“…The results confirm that the winds are the principal mechanism of the Es layer formation at low latitudes, whereas the electric field plays a secondary role. Moro et al (2017) used the same model to analyze the equatorial Es layer formation during the magnetic storm that occurred in November 2004. The results showed that the vertical electric fields of the EEJ irregularity inferred from coherent radar data can suffer severe changes, disrupting the Es q layers.…”

On the Sources of the Ionospheric Variability in the South American Magnetic Anomaly During Solar Minimum

“…Therefore, there exists a gap in proper understanding the ionospheric variability in South America, especially in the Brazilian sector where there are some unique geophysical characteristics. One of them is the high magnetic declination angle that reaches approximately −20° in the equatorial region due to the dip equator secular displacement effect causing considerable changes in the Equatorial Electrojet and consequently in sporadic E (Es) layers (Denardini et al, ; Moro et al, , ; Moro et al, ; Resende et al, ). There is also a more pronounced energetic particle precipitation in the SAMA region (Moro et al, , ) when compared with other regions having the same latitudinal range, due to the global minimum in the intensity of the geomagnetic field.…”