Geomagnetism and Aeronomy最新文献

{"title":"Ionospheric Response to the 25–26 August 2018 Geomagnetic Storm Using Detrended GPS-TEC and Wavelet Spectral Analysis at Low-MID Latitude Stations","authors":"Devbrat Pundhir,&nbsp; Ashok Kumar","doi":"10.1134/S0016793226600128","DOIUrl":"10.1134/S0016793226600128","url":null,"abstract":"<p>This study investigates the ionospheric response to the moderate geomagnetic storm of 25–26 August 2018 (Dst_min ≈ –174 nT), using GPS-derived Total Electron Content (TEC) observations from six stations distributed across low and mid latitudes in the Indian and Asian sectors. A systematic detrending approach was applied to remove diurnal trends and long-period background variations, thereby isolating storm-driven disturbances. Continuous Wavelet Transform (CWT) analysis of the detrended TEC revealed statistically significant (95% confidence against first-order autoregressive (AR1) red-noise background) storm-associated oscillations in the 30–90-min range, corresponding to atmospheric gravity waves (AGWs) and medium-scale traveling ionospheric disturbances (MSTIDs). Low-latitude stations exhibited the strongest signatures, consistent with equatorial electrodynamic coupling and Equatorial Ionization Anomaly (EIA) modulation. A segmented CWT analysis effectively captured the pre-storm, main-phase, and recovery-phase evolution. These findings highlight coherent equatorward propagation of storm-induced AGWs/TIDs and demonstrate the utility of multi-station TEC-wavelet diagnostics for storm-ionosphere coupling studies.</p>","PeriodicalId":55597,"journal":{"name":"Geomagnetism and Aeronomy","volume":"66 3","pages":"99 - 110"},"PeriodicalIF":0.5,"publicationDate":"2026-07-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148909525","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"An Improved Ionospheric Disturbance Detection Method for GNSS with Time-Resolved FFT Averaging Ratio","authors":"Swapna Raghunath,&nbsp;Indrajit Pal,&nbsp;Sriramakavacham Ramacharan,&nbsp;Prasun Chakrabarti,&nbsp;Venkata Ratnam Devanaboyina","doi":"10.1134/S0016793226600104","DOIUrl":"10.1134/S0016793226600104","url":null,"abstract":"<p>The ionosphere exhibits rapid spatial and temporal variability, particularly during Geomagnetic storms and Equatorial Plasma Bubble (EPB) events which can severely degrade the performance of Global Navigation Satellite System (GNSS). Although, the Fast Fourier Transform (FFT) Averaging Ratio (FAR) algorithm effectively detects ionospheric irregularities, it is computationally intensive, lacks precise temporal resolution and may miss ionospheric disturbance events when most of the satellite PRNs are simultaneously corrupted. To overcome this limitation, the present study proposes a Time Resolved-FAR (TR-FAR) technique that operates on time averaged Vertical Total Electron Content (VTEC) at every epoch. The TR-FAR algorithm applies FFT over consecutive non-overlapping 30-min windows, enabling almost real-time detection of medium- and large-scale ionospheric disturbances. A disturbance is detected when the ratio of the mean to average Power Spectral Density within a window exceeds a predetermined Threshold. GNSS data from the low-latitude stations, IISC (13.02117° N, 77.57038° E) and HYDE (17.41728° N, 78.55088° E), for the year 2023 were analyzed. Case studies of severe geomagnetic storms on 23–24 April, demonstrate that TR-FAR successfully captures short-time ionospheric irregularities that are underestimated by daily FAR indices. Comparative analysis shows that TR-FAR detects medium- and large-scale ionospheric disturbances with significantly higher sensitivity than the Rate of TEC Index (ROTI) by suppressing link-dependent ionospheric variability. The ionospheric climatological analysis from TR-FAR algorithm reveals pronounced seasonal dependance, with number of disturbances during March equinox exceeding those of the September equinox by approximately 8%, indicating clear equinoctial asymmetry. During solstitial period, the occurrence of ionospheric disturbances is suppressed with number of ionospheric disturbances reduced by approximately 24% compared to equinoctial periods. However, localized enhancements during December solstice reflect winter anomaly. These results establish TR-FAR as a computationally efficient tool for GNSS based ionospheric disturbance monitoring.</p>","PeriodicalId":55597,"journal":{"name":"Geomagnetism and Aeronomy","volume":"66 2","pages":"80 - 98"},"PeriodicalIF":0.5,"publicationDate":"2026-06-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148268547","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Global Characterization of Bottomside Ionospheric Parameters (B0 and B1) Using FORMOSAT-7/COSMIC-2 Radio Occultation Observations and Evaluation of IRI-2020 during Solar Cycle 25","authors":"Iswariya S.,&nbsp;Mefe Moses,&nbsp;Daniel Okoh,&nbsp;Chiranjeevi G. Vivek,&nbsp;Sampad Kumar Panda","doi":"10.1134/S0016793226600062","DOIUrl":"10.1134/S0016793226600062","url":null,"abstract":"<p>The bottomside thickness (B0) and shape (B1) parameters are crucial for representing ionospheric electron density profiles below the F2 layer in the IRI (International Reference Ionosphere) model. In the present study, the comprehensive analysis of diurnal, seasonal, longitudinal, and latitudinal variations of B0 and B1 is conducted using FORMOSAT-7/COSMIC-2 radio occultation electron density profiles over 2019–2024 and compared with corresponding IRI-2020 submodels, namely Bil-2000, Gul-1987, and ABT-2009, under different seasonal and solar activity conditions. The results show that B0 and B1 are strongly controlled by geomagnetic latitude and seasons, with maximum values near the equator and an apparent hemispheric asymmetry during the solstice. The consistent coupling among hmF2, NmF2, B0, and B1 is observed in geomagnetic latitude with local time variation, indicating that their variability is controlled by the equatorial dynamics. The magnitude of B0 and B1 primarily increases through solar activity without altering the spatial structure. The longitudinal analysis reveals pronounced modulation in B0, especially during the equinox and summer under high solar activity, whereas B1 exhibits weaker longitudinal dependence. On comparison with IRI-2020, it is observed that the model produces the spatial structure but with systematic differences in magnitude and variability from the COSMIC-2-derived B0 and B1 parameters. The results highlight the importance of these parameters for characterizing low and mid-latitude bottomside ionospheric structure and provide an opportunity for improvements of the empirical ionospheric model.</p>","PeriodicalId":55597,"journal":{"name":"Geomagnetism and Aeronomy","volume":"66 2","pages":"62 - 79"},"PeriodicalIF":0.5,"publicationDate":"2026-05-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148268568","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Solar Eclipse of February 26, 2017, Observed from the SAMBA Magnetometer Network","authors":"J. A. Lazzús,&nbsp;I. Salfate","doi":"10.1134/S0016793225600031","DOIUrl":"10.1134/S0016793225600031","url":null,"abstract":"<p>A report on the geomagnetic variations observed in Chile and Antarctica during the annular solar eclipse of February 26, 2017, is presented. This eclipse was visible from southern Chile in the morning and ended in the Democratic Republic of the Congo at sunset. Using data from three SAMBA network stations positioned at different magnetic latitudes along the 0° geomagnetic longitude and around the path of annularity, we analyzed changes in the geomagnetic field’s <i>X</i>, <i>Y</i>, and <i>Z</i> components during the eclipse. A baseline method, derived from the quietest days of the month, was applied to isolate eclipse-induced disturbances. Our analysis shows a decrease in the <i>X</i> component, an increase in the <i>Y</i> component, and a flattening of the <i>Z</i> component in synchrony with the eclipse. In addition, an analysis of ULF Pc3 pulsations reveals a localized attenuation of wave amplitudes during the eclipse, particularly near the umbral path. These results align with theoretical predictions and previous observations, suggesting a strong influence of the solar eclipse on the observed geomagnetic variations. The study reinforces the role of solar radiation reduction in modulating ionospheric currents and provides insights into the Earth’s magnetospheric response during these events. The study provides evidence of the role of solar radiation in regulating ionospheric currents and geomagnetic field variations in response to transient solar events, particularly in the Chile-Antarctica sector.</p>","PeriodicalId":55597,"journal":{"name":"Geomagnetism and Aeronomy","volume":"66 2","pages":"55 - 61"},"PeriodicalIF":0.5,"publicationDate":"2026-05-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148268567","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Earthquake-Induced Ionospheric TEC Variations Analysis over Indonesia during 2004–2024 and Comparison with Median/NeQuick TEC","authors":"R. Mukesh,&nbsp;S. Kiruthiga,&nbsp;S. Karthick,&nbsp;Sarat C. Dass,&nbsp;P. Priyavarshini","doi":"10.1134/S0016793226600025","DOIUrl":"10.1134/S0016793226600025","url":null,"abstract":"<p>The ionospheric layer contains free electrons and charged particles, which influence the propagation of radio signals. Total electron content (TEC) is a significant ionospheric parameter that represents the total number of electrons along the path between a radio transmitter and a receiver. Variations in TEC can affect communication and navigation systems and are mainly changed by solar ultraviolet radiation, geomagnetic storms, and atmospheric waves initiating from the lower atmosphere. Besides these activities, earthquakes can also cause TEC disturbances in the ionosphere. This research studies the TEC variations of five significant earthquakes of magnitude greater than 5.9 Mw that happened in Indonesia between the years 2004 and 2024. To do this study, we have selected the earthquakes that include the Western New Guinea, Wharton Basin, Papua, Maluku, and Sarangani events. The required TEC data was recorded from the BAKO GNSS station in Indonesia. In the case of each selected earthquake, TEC values of 30 days prior to that particular earthquake were used in the estimation of median TEC. A comparative analysis is carried out among the observed True TEC, Median TEC, and NeQuick model TEC for five days before and one day after each quake. This comparison is evaluated based on the statistical parameters such as the Root Mean Square Error (RMSE), Mean Absolute Gross Error (MAGE), Nash–Sutcliffe Efficiency (NSE), and Spearman Correlation Coefficient (SCC). The result indicates that the Median TEC is closer to the observed true TEC compared to the NeQuick TEC during these earthquake periods. The variations of TEC were observed at the time of the earthquake; this indicates variations that occurred due to changes in the ionosphere. This study helps to understand the relationship between earthquakes and disturbances in the ionosphere, which will be very effective in doing further research related to seismic studies.</p>","PeriodicalId":55597,"journal":{"name":"Geomagnetism and Aeronomy","volume":"66 1","pages":"11 - 28"},"PeriodicalIF":0.7,"publicationDate":"2026-05-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148009690","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Evaluating the Performance of GNSS NTCM-G Ionospheric Broadcast Model over the Indian Low-Latitude Region","authors":"Chakali Raja Sekhar,&nbsp; Devanaboyina Venkata Ratnam","doi":"10.1134/S0016793226600049","DOIUrl":"10.1134/S0016793226600049","url":null,"abstract":"<p>Users of the single frequency (SF) Global Navigation Satellite System (GNSS) are most affected by ionospheric delay, especially when solar and geomagnetic activity are at their strongest. Predicting the ionosphere total electron content (TEC) accordingly is therefore crucial for better replacement. Using Seasonal conditions and two intense geomagnetic storms that happened on 1 January and 12 November 2025, during solar cycle 25. This study examine the performance of three broadcast models over the low latitude Indian region. The models are Klobuchar (GPS), NeQuick-G (Galileo) and Neustrelitz TEC Model for Galileo (NTCM-G). we compare the TEC estimation from four GNSS stations (DRDN, BHPL, HYDE, and IISC), spanning low to high latitudes, are validated against the UPCG Global Ionospheric Map (GIM). Model performance is assessed using mean absolute error (MAE) and root mean square error (RMSE). Results show that the NTCM-G model consistently outperforms the Klobuchar and NeQuick-G models under both quiet and disturbed conditions. During the January storm, the NTCM-G model achieves a minimum RMSE of 11.68 TECU, while corresponding errors for NeQuick-G and Klobuchar reach 27.61 TECU and 22.63 TECU, respectively. Similar improvements are observed during the November storm event. Overall, the NTCM-G model demonstrates superior robustness in capturing seasonal variability and storm-time ionospheric disturbances, highlighting its suitability for enhanced ionospheric correction for SF GNSS applications over low-latitude regions.</p>","PeriodicalId":55597,"journal":{"name":"Geomagnetism and Aeronomy","volume":"66 1","pages":"29 - 40"},"PeriodicalIF":0.7,"publicationDate":"2026-05-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148009688","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Ionospheric Disturbance Monitoring during Typhoon Hagibis Based on GNSS G/SBased Joint Technology","authors":"Jianfeng Li,&nbsp;Fang Wang,&nbsp;Ding Yang,&nbsp;Yunhui Xiang","doi":"10.1134/S0016793226600013","DOIUrl":"10.1134/S0016793226600013","url":null,"abstract":"<p>Typhoon formation and development in the ocean area, leading to a major challenge in the study of ionospheric response to typhoon is the sparse distribution of observation sites. To address this limitation, this study proposes a ground and space based (G/SBased) joint ionospheric detection technique that integrates data from ground-based Global Navigation Satellite System (GNSS) receivers and Low Earth Orbit (LEO) satellites. The approach combines LEO-derived Total Electron Content (TEC) with ground-based GNSS-TEC for unified ionospheric modeling. Prior to integration, the LEO-TEC is adjusted using the Chapman function to ensure consistency with the vertical sensing altitude of the ground-based GNSS-TEC. This innovative approach was applied to examine ionospheric anomalies during Super Typhoon Hagibis (1919). The results demonstrate that the G/SBased joint detection method effectively addresses the spatial sparsity of ground based GNSS sites over oceans, substantially increasing both the quantity and spatial homogeneity of ionospheric piercing points (IPPs). This approach resolves the issue of TEC overfitting associated with uneven IPP distribution in ground based GNSS monitoring. Comparative analysis reveals that the G/SBased technique significantly enhances TEC retrieval accuracy in the typhoon’s core region, reducing the mean error (ME) from –3.98 to –0.67 TECU and the root mean square error (RMSE) from 5.83 to 5.16 TECU compared to standalone ground based GNSS measurements. Furthermore, the study identifies distinct ionospheric TEC anomalies in the typhoon center as it approached landfall. The G/SBased joint detection technique exhibits superior capabilities for monitoring typhoon-related ionospheric disturbances. By incorporating LEO satellite constellations, it overcomes the challenge of insufficient direct observation data over ocean areas, which otherwise hinders the use of GNSS observation data to detect typhoon induced ionospheric disturbances in remote seas.</p>","PeriodicalId":55597,"journal":{"name":"Geomagnetism and Aeronomy","volume":"66 1","pages":"41 - 53"},"PeriodicalIF":0.7,"publicationDate":"2026-05-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148009689","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Ionospheric Response to Recent Strong Geomagnetic Storm at Low, Mid, and High Latitudes Using GPS-TEC Observations","authors":"Devbrat Pundhir","doi":"10.1134/S0016793225600304","DOIUrl":"10.1134/S0016793225600304","url":null,"abstract":"<p>The ionospheric response to the intense geomagnetic storm of 10–13 November 2025 is investigated using multi-latitude GNSS-derived total electron content (TEC), ground magnetic field observations, and geomagnetic indices. The storm was characterized by a minimum Dst of –230 nT and elevated Kp values exceeding 8, while the solar flux F10.7 remained relatively stable. Differential TEC (dTEC) analysis reveals a strong latitude dependence of storm-time ionospheric perturbations. Low-latitude stations exhibit relatively smooth variations within ±15 TECU, mid-latitude stations show enhanced and structured responses reaching ±30–35 TECU, and high-latitude stations experience the largest disturbances, with dTEC values exceeding –40 to –45 TECU during the main phase. Ground magnetic field data indicate increasing disturbance amplitudes with latitude, and wavelet analysis of TEC residuals shows enhanced power during the storm main and early recovery phases, with dominant shorter-period fluctuations at higher latitudes. These results demonstrate the significant latitude-dependent impact of intense geomagnetic storms on ionospheric TEC and highlight the importance of multi-latitude GNSS observations for characterizing storm-time ionospheric variability. Pre-storm analysis shows that TEC variability during the 2–3 days prior to the sudden storm commencement (SSC) remained comparable to quiet-time levels, with no coherent ionospheric precursor. These results demonstrate a pronounced latitude-dependent ionospheric response to intense geomagnetic storms and highlight the importance of coordinated multi-latitude GNSS observations for understanding storm-time magnetosphere–ionosphere–thermosphere coupling.</p>","PeriodicalId":55597,"journal":{"name":"Geomagnetism and Aeronomy","volume":"66 1","pages":"1 - 10"},"PeriodicalIF":0.7,"publicationDate":"2026-04-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148009811","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Total Electron Content Variability in Response to Solar Flares and a Geomagnetic Storm Over East Africa during May 8–15, 2024","authors":"Lamessa Tamasgen Mogasa,&nbsp; Dejene Ambisa Terefe","doi":"10.1134/S0016793225600237","DOIUrl":"10.1134/S0016793225600237","url":null,"abstract":"<p>This study investigates the ionospheric response over the East Africa region during solar flares and a geomagnetic storm from 8–15 May 2024. During this period, 12 X-class solar flares and one extreme geomagnetic storm occurred, causing pronounced variability in total electron content (TEC). X-ray flux measurements from the Extreme Ultraviolet and X-ray Irradiance Sensors (EXIS) on board the Geostationary Operational Environmental Satellites (GOES) are analyzed to detect solar flares. TEC derived from four GNSS receiver stations and the IRI-2020 model, O/N₂ ratio maps, and an ionospheric electric fields model are used to identify ionospheric variation owing to the space weather events. The X-class flares prior to May 11 produced immediate TEC enhancements of up to +15 TECU relative to quiet day levels, consistent with sudden ionospheric disturbances. In contrast, the geomagnetic storm on May 10–11 induced both positive and negative storm phases, with TEC deviations ranging from –31.46 to +33.13 TECU. During the main phase of the geomagnetic storm, at the ADIS station, TEC increased by +10.8 TECU and then decreased by –8 TECU. In the recovery phase, it increased to +31 TECU. At the DJIG station during the main phase, TEC decreased by –16.1 TECU, followed by a significant positive enhancement reaching +30.5 TECU on May 12th. Similarly, the MAL2 station recorded a minimum negative TEC deviation of –16.6 TECU during the main phase, with a notable maximum positive deviation of +33.03 TECU also occurring on May 12th. For the MBAR station, the main storm phase on May 10th showed a minimum negative TEC deviation of –15.94 TECU, and a maximum positive deviation of +33.13 TECU was observed on May 12th. We have used correlation coefficients (<span>(r)</span>), Percentage Root-Mean Square Error (PRMSE) and root mean square errors (RMSE) to examine the variation of the IRI-2020 TEC from the GPS TEC during the storm. The results show that the model performed best at the ADIS station, with the highest <span>(r)</span> (0.93) and the lowest RMSE (13.33) and PRMSE (28.31%). These study enhance our understanding of solar flare and geomagnetic storm impacts in equatorial and low latitude regions, which is crucial for improving space weather forecasting and mitigating risks.</p>","PeriodicalId":55597,"journal":{"name":"Geomagnetism and Aeronomy","volume":"65 7-8","pages":"174 - 186"},"PeriodicalIF":0.7,"publicationDate":"2026-02-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147341575","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Ionospheric Responses in the Low-Latitude Region of Africa during the Geomagnetic Storm of 27 August 2021","authors":"Chukwuma Moses Anoruo,&nbsp; Francisca Nneka Okeke","doi":"10.1134/S0016793225600286","DOIUrl":"10.1134/S0016793225600286","url":null,"abstract":"<p>In this paper, we employ equatorial-latitude Global Navigation Satellite System (GNSS) data from TERONET to investigate the storm that occurred on August 27, 2021. To characterize the equatorial and mid-latitude ionosphere during the storm, the 10 quietest days of August 2021 were selected as background TECs, and we calculated the relative TEC (rTEC) from the deviation of the disturbed days using a median value of the TEC at each timestep, considering all 10 days and selecting the threshold |–30 ≤ rTEC ≥ 30| for the TEC anomaly. Additionally, we employ the African geodetic reference frame (AFREF) GNSS network to analyze the data from 19 stations in the African region during storms. We employ ROTI_ave as a proxy for scintillation to study irregularities and GNSS fluctuations during storm main and recovery phases and examine thermospheric variations from the [O]/[N₂] ratio. Again, we employ the depression of the horizontal component (<i>H</i>) of the Earth’s magnetic field obtained from equatorial and mid-latitude magnetometers to feature the seeding of the TEC enhancements and depression. Our major findings reveal that ionospheric irregularities at low latitudes, as observed from GNSS measurements, show distinct latitudinal differences and seem not well experienced at the dip equator. The equatorial and mid-latitude ionosphere of the Africa sector shows a complex irregularity occurrence that may not have a stronger effect of the solar activity cycle but seems to follow storm-enhanced density, where morning-hour positive storms govern irregularities during the commencement of storms preceded by the equatorial ionization anomaly (EIA) due to localized expansion of the neutral atmosphere. </p>","PeriodicalId":55597,"journal":{"name":"Geomagnetism and Aeronomy","volume":"65 7-8","pages":"159 - 173"},"PeriodicalIF":0.7,"publicationDate":"2026-02-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147341576","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}