In this paper, we study the geomagnetic storm that occurred on 23–24 April 2023. We present variations in the values of interplanetary magnetic field (IMF-Bz), solar wind parameters (Vsw, Nsw, Tsw, and Psw), geomagnetic index (SYM-H), and vertical total electron content (VTEC) obtained from 18 GPS-TEC stations situated in equatorial, mid-latitude, and high-latitude regions. We analyze the variations in total electron content (TEC) before, during, and after the storm using VTEC plots, dTEC% plots, and global ionospheric maps for each GNSS receiver station, all referenced to universal time (UT). Our results indicate that GNSS receiver stations located at high latitudes detected an increase in ionospheric density during the main phase and a decrease during the recovery phase. In contrast, stations in equatorial and mid-latitude regions detected a decrease in ionospheric density during the main phase and an increase during the recovery phase. Large dTEC% values ranging from −80 to 190 TECU were observed a few hours before and during the storm period (23–24 April 2023); these can be compared to values ranging from −10 to 20 TECU on the day before (22 April 2023) and the day after (25 April 2023). Notably, higher dTEC% values were observed at stations in high and middle latitudes compared to those in the equatorial region. As the storm progressed, the TEC intensification observed on global ionospheric maps appeared to shift from east to west. A detailed analysis of these maps showed that equatorial and low-latitude regions experienced larger spatial and temporal TEC variations during the storm period compared to higher-latitude regions.

The annular solar eclipse of 21 June 2020, provided a valuable opportunity to examine the ionospheric response to celestial events. This study analyzes variations in Vertical Total electron content (VTEC) over the equatorial region using data from the UQRG Global Ionospheric Map (GIM), ground‐based GPS‐TEC measurements, and equatorial electrojet (EEJ) strength from magnetometers near the eclipse path. Significant VTEC reductions were observed during the eclipse. The early decline began in East Africa and South Asia during the morning hours, while in the Western Pacific region, the reduction occurred in the late afternoon, coinciding with the onset of the eclipse. Around local noon, a delayed decrease was detected at stations located in Southeast and East Asia. 22%–53% VTEC reduction was recorded during the eclipse's main phase, with effects persisting from 35 min to over 8 hr post‐eclipse. Post‐eclipse variations in dusk sector suggest local electrodynamical effects. The study found no significant impact on EEJ strength between E to E, and no substantial counter equatorial electrojet was detected. Conducted during the monsoon season and the longest day of the year, observed VTEC reductions likely result from eclipse‐induced pressure changes and cooling effects. GIM visualizations showed that dVTEC% decreased by up to 40% globally. The findings indicate that VTEC decreases are not strongly correlated with obscuration percentage, highlighting complexity of ionospheric responses. This study enhances understanding of eclipse‐driven ionospheric variability, emphasizing the role of photoionization, recombination, geographic location, and local time, with implications for space weather forecasting and ionospheric modeling.

In this paper, we study the geomagnetic storm that occurred on April 23–24, 2023. We present variations in the interplanetary magnetic field (IMF-Bz), solar wind parameters (Vsw, Nsw, Tsw, and Psw), geomagnetic index (SYM-H), and vertical total electron content (VTEC) derived from 18 GPS-TEC stations situated in equatorial, mid-latitude, and high-latitude regions. We analyze the Total Electron Content (TEC) variations before, during, and after the storm using VTEC plots, dTEC% plots, and global ionospheric maps for each GNSS receiver station, all referenced to Universal Time (UT). Our results indicate that GNSS receiver stations located at high latitudes exhibited an increase in ionospheric density structures during the main phase and a decrease during the recovery phase. In contrast, stations in equatorial and mid-latitude regions showed a decrease in ionospheric density during the main phase and an increase during the recovery phase. Large dTEC% values ranging from − 80 to 190 TECU were observed a few hours before and during the storm period (April 23–24, 2023), compared to values ranging from − 10 to 20 TECU on the day before (April 22, 2023) and the day after (April 25, 2023). Notably, higher dTEC% values were observed at stations in high and mid-latitudes compared to those in the equatorial region. As the storm progressed, the TEC intensification observed on global ionospheric maps appeared to shift from east to west. A detailed analysis of these maps showed that equatorial and low-latitude regions experienced the highest spatial and temporal TEC variations during the storm period compared to higher latitude regions.

We investigate the ionospheric response to the intense St. Patrick's Day geomagnetic storm of 17 March 2015 (minimum Dst ≈ −223 nT) using Global Navigation Satellite System (GNSS)–derived Total Electron Content (TEC) observations from 11 East African stations: Addis Ababa‐ADIS (9.04°N, 38.77°E), Arusha‐ARSH (3.38°S, 36.69°E), Dodoma‐DODM (6.19°S, 35.75°E), Eldoret‐MOIU (0.29°N, 35.29°E), Malindi‐MAL2 (2.99°S, 40.19°E), Mbarara‐MBAR (0.61°S, 30.65°E), and Mbeya‐MBEY (9.03°N, 38.74°E, Asab‐ASAB (13.06°N. 43.65°E), Ginr‐GINR (7.15°N, 40.71°E), Bahir Dar‐BDMT (11.60°N, 37.36°E), Debarek‐DEBK (13.15°N, 37.89°E), Assosa‐ASOS (10.05°N, 34.55°E). Instrumental biases were removed, data were screened for satellite elevation angles ≥40°, and analyzed using detrended TEC (dTEC) and Morlet continuous wavelet transform to identify storm‐time ionospheric disturbances across multiple temporal scales. The storm main phase was characterized by prolonged southward z‐component of interplanetary magnetic field (IMF‐Bz) (<−20 nT), enhanced solar wind speeds (>600 kms ⁻¹ ), and elevated y‐component of the interplanetary electric field (IEF‐Ey), indicating strong solar wind–magnetosphere coupling. These conditions drove significant ionospheric variability, with the largest dTEC amplitudes (>±4 TECU) observed near the Equatorial Ionization Anomaly (EIA), particularly at ADIS and MAL2. Wavelet analysis revealed the coexistence of medium‐scale traveling ionospheric disturbances (MSTIDs; ∼0.25–1 hr), large‐scale travelling ionospheric disturbances (LSTIDs; ∼1–4 hr), and short‐period fluctuations (<0.25 hr). Disturbances were most pronounced during the storm main and early recovery phases and exhibited clear latitudinal dependence, with enhanced activity near the EIA crest. Post‐sunset ionospheric irregularities, interpreted as equatorial plasma bubbles (EPBs), were identified through sharp dTEC depletions and enhanced short‐period wavelet power. EPBs occurred on most days but showed increased frequency, earlier onset, and wider latitudinal extent during the storm, consistent with intensified pre‐reversal enhancement and storm‐time electric field penetration. The temporal association between MSTIDs and EPB onset suggests a potential seeding role of atmospheric wave activity. These results demonstrate that ionospheric disturbances over East Africa are strongly controlled by the interplay between storm‐time electrodynamics and equatorial processes. The study highlights the effectiveness of combined dTEC and wavelet analysis for resolving multiscale ionospheric variability and provides important insights into space weather impacts on GNSS performance in equatorial regions.

N this study We utilized GPS - based TEC data from four ground based stations: Thule, Greenland and Ny-Alesund, Norway in the Northern hemisphere, and Syogo and Palmer in the Southern Hemisphere. While earlier studies have explored storm-time TEC fluctuations caused by mechanisms such as prompt penetration Electric fields (PPEF), disturbance dynamo effects , and thermospheric composition changes, high-latitude ionospheric behaivor- particularly during this specific storm has received relatively little attention. Furthermore, important irregularities like ploar cap patches and subauroral ion drifts remain underexplored in hemispheric comparisons. This work fills a critical gap by presenting a comparative , high-resolution analysis of Vertical TEC in both hemispheres, integrating key geophysical drivers such as Polar cap index, AE(AL/AU) indices, IMF B_z, and SYM-H. Results reveal distinct hemispheric responses: VTEC peaks at ∼ 19 TECU (Thule), ∼ 10 TECU (Ny-Ålesund), ∼ 21 TECU (Syowa), and ∼ 22 TECU (Palmer), with stronger variability observed in SH stations. These differences are attributed to enhanced solar EUV exposure, hemispheric magnetic field assymetries, and intensified particle precipitation during storm-time electrodynamic conditions. By providing new insights into the dynamics of magnetosphere-ionosphere coupling during geomagnetic storms. This study contributes to a more comprehensive understanding of high-latitude space weather effects and sets the stage for future modeling and monitoring efforts.