## 1 Introduction
This current is approximately twice as strong as the mid-latitude solar-quiet (Sq) ionospheric current [24]. 3. Equatorial plasma bubbles (EPB) related to the pre-reversal enhancement (PRE) of the eastward electric field around sunset [25; 26; 27]. The electric field is eastward during the day and westward during night, and the PRE occurs as an eastward electric field increases before turning westward at sunset. The PRE associated with the sharp ionospheric depletion at sunset creates a Rayleigh Taylor instability at the origin of EPB. During geomagnetic storms, the equatorial ionosphere is coupled with the high latitude ionosphere through electrodynamics and related factors: 1. Transmission of electric fields related to the motion of particles in the magnetosphere, namely Prompt Penetration Electric Field (PPEF) [28]. 2. The electrojet in the auroral zone (ionospheric electric currents) dissipates energy through Joule heating and produces a thermal expansion of the atmosphere (variations in pressure, temperature, and motion) [29]. 3. Motions of the neutral atmosphere by disturbance dynamo electric fields (DDEF) [30; 31]. TEC enhancements during geomagnetic storms have been widely studied on regional and global scales. Several authors have specifically looked for latitudinal and longitudinal dependencies with multi-instrumental observations (e.g., [32; 33; 34; 35]). Ref. [30] studied the modelling of DDEF at mid-latitudes and showed the existence of electric current cells, which is a very interesting finding for studies on low-latitude magnetic disturbances due to ionospheric DDEF on a planetary scale. Ref. [36] observed similar effects at two zonal sectors separated by 12 h in LST during an intense geomagnetic storm. The southward IMF B\({}_{\rm z}\) caused an eastward electric-field drift in the daytime sector, and then westward in the night side [37]. Ref. [38] showed the redistribution of plasma in the low-latitude ionosphere under electrodynamics processes of the E and F regions, and [39] examined the low-latitude ionosphere for different longitudes. They showed no significant longitudinal variations in the electron densities. The EIA crests can reach up to \(\pm 20\) degrees of the magnetic latitude during geomagnetic storms [40], and the PPEF of westward polarity during the night side has Earth directed to a downward drift, which results in plasma depletion at the low-latitude regions. Ref. [41] performed a complete analysis of the storm-time ionospheric responses at different stations in the equatorial regions and provided similar evidence during storm time periods in the form of ion drift and EEJ variability, but the authors found a lack of variations in the ionosphere due to PPEF, except for South America. The authors investigated the correlation of storm-time enhancements in South America during the local morning with PPEF peaks, while the African and Asian sectors showed ionospheric variations before the PPEF. Ionospheric variations before the PPEF have been shown in the African and Asian sectors [41], where the energetic particle input may strengthen the enhancements of TEC. Ref. [42] investigated TEC enhancements at the low-latitude GNSS stations of Japan using a 27-day running-median window and stated a possible relation to the equatorial crest expansion. The expansion of the EIA to mid-latitude regions has been reported in [16]. The authors investigated the main phase of the August 2018 geomagnetic storm in the South American sector using GNSS TEC and other satellite data. In their work, storm-time ionospheric variations were attributed to PPEF and DDEF variability, which prompted EIA expansion to higher latitude regions. Ref. [40] studied the same storm and found medium-scale positive and negative ionospheric disturbances at middle and high latitudes that were attributed to a storm-enhanced density (SED)-plume, mid-latitude ionospheric trough, particle precipitation in the auroral zone, and equatorial plasma bubbles in South America.