Ionospheric TEC variations during an intense geomagnetic storm on 11 May 2024

Ionospheric TEC variations during an intense geomagnetic storm on 11 May 2024 | Research Square window.SnipcartSettings = { analytics: { enabled: false } }; (function() { var accessVector = localStorage.getItem('access_vector') || ''; window.dataLayer = window.dataLayer || []; if (accessVector) { window.dataLayer.push({ user: { profile: { profileInfo: { snid: accessVector } } } }); } })(); (function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start':new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0],j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src='https://www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f);})(window,document,'script','dataLayer','GTM-K279D39R'); Browse Preprints In Review Journals COVID-19 Preprints AJE Video Bytes Research Tools Research Promotion AJE Professional Editing AJE Rubriq About Preprint Platform In Review Editorial Policies Our Team Advisory Board Help Center Sign In Submit a Preprint Cite Share Download PDF Research Article Ionospheric TEC variations during an intense geomagnetic storm on 11 May 2024 Chaithra P, Kamsali Nagaraja This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-4691095/v1 This work is licensed under a CC BY 4.0 License Status: Posted Version 1 posted You are reading this latest preprint version Abstract On May 11, 2024, a severe geomagnetic storm occurred, causing significant disruptions to Earth’s magnetosphere and ionosphere. These storms, primarily caused by solar activity, are distinguished by variations in solar wind that increase energy flow from the Sun to Earth. The present research aims to analyze the latitudinal response of ionospheric Total Electron Content (TEC) during this event. The analysis is based on data collected from three different geographic locations: IISC (13.02°N, 77.57°E), POL2 (42.68°N, 74.69°E), and NOVM (55.03°N, 82.91°E). The electron density of the ionosphere is crucial for satellite-based communication and navigation systems. Geomagnetic storm strength is measured by the Kp-index and Disturbance storm time (Dst) index. During a geomagnetic storm and X-class flare of magnitude 5.89, a maximum Dst index of -412 nT and Kp index of 9 are observed during the storm day. TEC values increased at IISc during the storm period compared to quiet days, but decreased over POL2 and NOVM stations. A good correlation was observed between the observed TEC during a storm day and the predicted TEC by the IRI-2020 model over IISC and NOVM, while moderate correlation was observed over POL2. Ionosphere TEC Earth Sun Geomagnetic Storm Solar flare Figures Figure 1 Figure 2 Figure 3 Figure 4 1. Introduction The temporal and spatial variability of Earth’s ionosphere is significant in space weather. The variability is highly influenced by multiple strong coupling processes (Saranya et al., 2015 ). Solar activity such as Coronal Mass Ejections (CMEs) and high-speed solar wind streams, interact with the Earth’s magnetosphere to cause geomagnetic storms. The interactions cause greater plasma circulation within the magnetosphere, resulting in high electric currents and fields (Gonzalez et al., 1994 ). Storms have an impact on the Earth's ionosphere, causing fluctuations in Total Electron Content (TEC). TEC is an important indicator that quantifies the number of electrons inside a vertical column of the ionosphere, spanning from 50 km to 1000 km above the Earth’s surface (Bhattarai et al., 2018 ) and 1 TEC unit = 1×10 16 electrons/m 2 . Significant information on the effects of space weather on satellite systems, communication, and navigation may be obtained by comprehending the latitudinal response of ionospheric thermoelectric conduction during geomagnetic storms (Kintner et al., 2007). Specific features of low-latitude and equatorial ionosphere include the electrodynamics of the plasma fountain, the equatorial electrojet (EEJ), the equatorial ionization anomaly (EIA), and the development of equatorial plasma bubbles after sunset (Panda et al., 2013 ; Harsha et al., 2020; Ghanshyam et al., 2023). The EIA consists of two crests of increased TEC centered around ± 15° magnetic latitude, separated by a trough along the magnetic equator (Appleton 1946 ; Olwendo et al., 2017 ; Ghanshyam et al., 2023). The equatorial plasma fountain phenomenon elevates ionospheric plasma to greater heights, resulting in its dispersion along magnetic field lines and the formation of crests (Anderson, 1981 ). The EIA results from the eastward electric fields that occur during daytime, which also contribute to the equatorial ionospheric fountain effect (Appleton, 1946 ). This phenomenon is caused by an upward drift in E×B a result of the interaction between the horizontal northward magnetic fields and the eastward electric fields near the equator. Panda et al. ( 2013 ) state that the plasma is elevated by a vertical movement and transported to greater altitudes. From there, it moves to higher latitudes via magnetic field lines. The plasma flow at magnetic latitudes ± 15° is responsible for the production of EIA peaks (Kelley, 2009 ). The ionosphere receives a large amount of energy from powerful geomagnetic storms that occur at high latitudes. This energy is responsible for the production of currents, electric fields, and Joule heating. Disturbed winds and disturbance dynamo processes may have an impact on ionospheric electric currents and fields. These storms may disrupt the equatorial ionosphere by shifting electric fields from high to low latitudes (Sastri et al., 2000 ). Storms cause two groups of electric fields. The first one is called the disturbance dynamo electric field (DDEF), which can persist for more than a day. It counteracts the normal zonal electric field during quiet periods and shifts westward during the day and eastward during the night. The second type is the transitory prompt penetration electric field (PPEF), generated by the solar wind's magnetospheric dynamo. This electric field moves westward at night and eastward during the day. This PPEF lasts only a few hours. That means that during a storm, the eastward electric field during the daytime can change, which can increase or decrease the plasma fountain effect (Lin et al., 2007 ; Olwendo et al., 2017 ). Mannucci et al. ( 2005 ) investigated the impact of a Halloween storm, with a disturbance storm time index (Dst) of -390 nT, on fluctuations in the total electron content of the ionosphere. The study showed that plasma transport towards the pole and potential uplift at mid-latitudes contribute to significant increase in mid-latitude plasma, which may lead to high TEC differences and TEC plumes resulting from subauroral electric fields. Sharma et al. ( 2011 ) conducted a study on the TEC of the ionosphere at low latitudes in response to a geomagnetic storm that occurred on August 25, 2005. The storm had a Dst value of -184 nT. During the storm, the TEC records a peak with two distinct humps, which have an amplitude about twice as large as that observed on a quiet day. The second peak belongs to the plasma fountain effect, whereas the first peak is assigned to the PPEF. In addition, it has been shown that the impact of the PPEF is nearly uniform in the longitudinal direction. Ikubanni et al. ( 2020 ) studied the impact of intense geomagnetic storms on TEC in the low-latitude area of Africa. March 17, 2013, geomagnetic storm (Dst = -132 nT) had a substantial influence at commencement of recovery phase, particularly at Equatorial Ionization Anomaly (EIA) crest site. On the other hand, March 17, 2015 storm (Dst = -234 nT) event had a significant impact near the end of the main phase and during recovery phase. VTEC reactions have been analysed during a geomagnetic storm (Dst = -175 nT) from August 24 to 31, 2018, and found that the VTEC peak on August 26, 2018 was produced by the PPEF from a geomagnetic storm (Sur et al. 2020 ). The corresponding decrease in VTEC over the subsequent days was attributed to DDEF during the storm’s recovery phase. The impact of four strong geomagnetic storms that occurred between 2010 and 2015 on fluctuations in Total Electron Content (TEC) in low-latitude areas of India (Singh et al. 2021 ). They found that the notable changes in TEC during the storm period were mostly attributed to the electric field and neutral winds associated with the storms. Geomagnetic storms cause substantial fluctuations in the electron density of the ionosphere, which are often measured as total electron content (TEC). These storms induce ionospheric perturbations that may either increase or decrease electron density. This research investigates the variations in ionospheric TEC at various locations across the planet Earth during the May 11, 2024, which is the most severe (Dst = -412 nT) to be observed after the Halloween storm that occurred on October 29–30, 2003 (Dst = -390 nT). 2. Data and method of analysis This research analyzes data from three distinct geographic sites, namely IISC (13.02°N, 77.57°E), POL2 (42.68°N, 74.69°E), and NOVM (55.03°N, 82.91°E), to examine the latitudinal reaction of ionospheric TEC during the geomagnetic storms. These stations are situated in latitudes ranging from low to mid, which enables a thorough investigation of the impact of the geomagnetic storm across different latitudes. The selection of GPS stations in this study was based on their geographical and geomagnetic coordinates, which are shown in Table-1. The IISC is situated inside the EIA area, although the stations POL2 and NOVM are located outside of it. Ionospheric TEC data is obtained by obtaining the RINEX file from the International GNSS Station (IGS), which may be accessed at the following link: https://cddis.nasa.gov/Data_and_Derived_Products/GNSS/broadcast_ephemeris_data.html . Gopi Seemala’s GPS-TEC software package is used to process this data. Reddybattula et al. ( 2019 ) provide a comprehensive elucidation of the operational basis of the program. Figure 1 displays the several sites of the IGS network on the Earth’s surface that were chosen for this study. Table-1: GPS stations with geographic and geomagnetic coordinates used in the study Station code Geographic coordinates Geomagnetic coordinates Latitude Longitude Latitude Longitude NOVM 55.03 N 82.91 E 46.31 N 159.81 E POL2 42.68 N 74.69 E 34.55 N 151.09 E IISC 13.02 N 77.57 E 4.90 N 150.93 E The disturbed storm time (Dst) index is used to measure the intensity of a geomagnetic storm. The geomagnetic storms are categorised as moderate (-50 nT ≥ Dst > -100 nT), strong (-100 nT ≥ Dst > -200 nT), and extreme (-200 nT ≥ Dst) based on higher deviation of Dst index from undisturbed duration (Gonzalez et al., 1994 ). Gosling et al. ( 1991 ) classified geomagnetic storms into several categories based on the Kp index of 3-hour values. These categories include weak (Kp ≤ 5), moderate (Kp = 6), strong (Kp = 7), and severe storms (Kp ≥ 8). The Dst and Kp indices data were obtained from Kyoto Geomagnetic Data Service via https://wdc.kugi.kyoto-u.ac.jp/wdc/Sec3.html . Intensity of solar flare data was retrieved from the National Oceanic and Atmospheric Administration (NOAA) through https://www.swpc.noaa.gov/products/goes-x-ray-flux . The NOAA/GOES XRS classifies solar flare intensities, which spans a wide range, on their peak emissions in soft x-ray (0.1–0.8 nm) spectral region. The solar flares are classified as A-class begins at 10 − 8 Wm -2 as the initial x-ray flux level, B-class (≥ 10 − 7 Wm -2 ), C- class (10 − 6 Wm- 2 ), M-class (10 − 5 Wm- 2 ), and X-class (10 − 4 Wm- 2 ) flares. TEC data obtained is compared with the TEC data predicted by the IRI-2021 model throughout a geomagnetic storm. 3. Results and Discussions An analysis was conducted on the Ionospheric TEC observations obtained from three GNSS receiver stations, namely IISC, POL2, and NOVM. The observations were made over five days during May 09–13, 2024, encompassing the day before, during, and after a geomagnetic storm. A substantial decrease in the Dst index, which quantifies the disturbance in the Earth's magnetic field, indicated the beginning of a severe storm. During the present observation period, the Dst index attained a value of -413 nT, indicating an intense geomagnetic storm. The significant level of geomagnetic activity was further validated by the Kp index attaining a value of 9, which quantifies geomagnetic activity on a scale ranging from 0 to 9. The measurements demonstrated the storm's intensity and the possibility of significant disruptions in the ionosphere. The TEC fluctuations over the three selected areas during the geomagnetic storm are depicted in Fig. 2 , together with the accompanying Dst and Kp index. The duration of the geomagnetic storm was about 24 hours, as seen by the darkened region in Fig. 2 . The Sudden Commencement of Storm (SCS) begins at 18:00 UT on May 10, 2024. The TEC values for the three sites show typical diurnal variations, with higher values during the daytime and lower values at nighttime. After SCS, the highest TEC recorded at the IISC station on May 11, 2024 was 96.16 TECU, which was notably higher than the values recorded from the previous days. The equatorial plasma fountain effect and the equatorial ionization anomaly (EIA) are responsible for an increase in TEC at IISC. The eastward electric field at the equator can be strengthened by penetration of electric fields from high latitudes during geomagnetic storms. Stronger E×B drift that raises the altitude of the ionospheric plasma, and from there, it diffuses along magnetic field lines forces to generate enhanced EIA crests (Fejer et al., 1999 ). Prompt Penetration Electric Fields (PPEFs) can also quickly reach the equator during intense storms, enhancing the EIA and increases the ionospheric TEC (Panda et al., 2015 ). The study demonstrates that there was a substantial decrease in Total Electron Content (TEC) measurements over the POL2 station during the geomagnetic storm. The highest TEC recorded on May 11, 2024 is 18.08 TECU, indicating a significant 59% reduction compared to preceding days characterized by minimal storm activity. The decrease in TEC at POL2 is primarily due to the intricate interplay between electric fields and thermospheric winds during the storm. Mid-latitude regions often experience the combined impacts of direct electric field penetration from higher latitudes and disturbance dynamo phenomena. The PPEFs initially cause a rapid rise in Total Electron Content. However, the ensuing disturbance dynamo generates westward electric fields during the daylight, which counteract the upward E×B drift and result in decreased TEC (Maruyama et al., 2005 ). Over NOVM location, the maximum TEC observed during geomagnetic storm on May 11, 2024 is 17.57 TECU, representing a 36% decrease in TEC compared to the previous days. Several high-latitude effects are responsible for the drop in TEC at NOVM, even though it is at the end of mid-latitudes. Auroral precipitation and electric fields at high latitudes may exert significant impacts. During geomagnetic storms, the auroral oval expands, leading to the precipitation of energetic particles into the ionosphere and an increase in ionization in the E-region. This leads to an elevation in recombination rates, resulting in a decrease in total electron content (TEC) in the F-region. Intense Joule heating may also cause the upward movement of neutral gas, leading to increased recombination rates and further reduction of Total Electron Content (TEC) at high altitudes (Fuller-Rowell et al., 1994 ). On May 11, 2024, a noticeable solar flare was also observed in addition to the geomagnetic storm. The solar flare was categorized as an X-class solar flare, signifying a very strong flare with the Intensity of the solar flare as 5.89×10 − 4 Wm -2 . The Fig. 3 shows the changes in the ionospheric TEC over the three stations chosen during extreme solar flare events. Solar flares are sudden and massive bursts of radiation from the sun that can produce significant changes in ionization within the Earth’s ionosphere. The fluctuations in the TEC over the selected three sites can be attributed to several causes including geomagnetic storm dynamics, ionospheric processes at various latitudes, and the impact of the X- class solar flares. The X 5.89 solar flare would have caused more ionization in the lower ionosphere, resulting in higher TEC values. Solar flares produce large quantities of X-rays and Extreme Ultra Violet (EUV) radiation, which substantially boosts ionization rates (Tsurutani et al., 2005 ). Further increased in the ionization along with geomagnetic storm effects would account for the increase in TEC over IISC. The X 5.89 solar flare caused considerable changes in TEC values, which were especially noticeable over POL2 and NOVM due to the high latitude’s sensitivity to geomagnetic disturbances and ionospheric coupling. The solar flare has led to an increase in ionization, which, when paired with the effects of geomagnetic storms, has created a notable initial rise in Total Electron Content. This increase is then followed by a sharp decrease owing to accelerated recombination and particle precipitation. The IRI-2020 (International Reference Ionosphere) model was used to investigate the ionosphere and assess the accuracy of our observed Total Electron Content (TEC) data, as seen in Fig. 3 , during the period of geomagnetic storm activity. The correlation coefficients (R²) were calculated to assess the relationship between the modelled and observed TEC values at all stations. The found correlation coefficients (R²) are as follows: R² = 0.80 for IISC, R² = 0.57 for POL2, and R² = 0.84 for NOVM. The correlations indicate a substantial concurrence between the observed and predicted TEC values at IISC and NOVM, whereas a modest correlation is reported at POL2. The IRI-2020 model demonstrates a robust connection at IISC and NOVM, suggesting its efficacy in accurately modeling the ionospheric behavior at lower and higher latitudes during periods of disturbance. The intricate behavior of the ionosphere at mid-latitudes during geomagnetic storms may not be fully represented by the model, as seen by the moderate correlation with the IRI-2020 model, indicating the presence of some discrepancies. 4. Conclusion The analysis of Total Electron Content (TEC) changes during an intense geomagnetic storm on May 11, 2024 reveals significant differences in ionospheric responses across various latitudes. The recorded TEC data was affected by both the geomagnetic storm and an X-class solar flare. At the low-latitude station IISC, the TEC data increased, whereas at the mid-latitudes POL2 and NOVM locations, it decreased. Disparities in the impact of the solar flare on TEC were observed based on latitude, namely at the NOVM, POL2, and IISC stations. The differing ionospheric response to the enhanced radiation and subsequent impacts of geomagnetic storms can account for this variance. The TEC values experienced a significant increase above the IISC during the storm that can be attributed to the equatorial plasma fountain effect and the equatorial ionization anomaly. The X 5.89 solar flare contributed to increased ionization, which led to higher TEC values. TEC values at POL2 decreased sharply throughout the storm, owing to complicated interactions between storm-time electric fields and thermospheric winds. A significant drop in TEC was found at NOVM, owing to high-latitude factors such as auroral precipitation and increased recombination rates caused by intense Joule heating. To minimize the effect of space weather on communication and navigation networks that rely on satellites, this research provides helpful information for enhancing ionospheric models and prediction tools. Declarations Author Contribution The research was carried out jointly with shared responsibilities, and both authors contributed to the manuscript. Chaithra P and Kamsali Nagaraja worked together to develop the concept, methodology, and formal analysis and conducted the investigation. Chaithra P and Kamsali Nagaraja were also involved in the initial drafting, revision, and editing of the manuscript in its entirety. Kamsali Nagaraja served as superviser for the research work and handled the resources. Acknowledgments The author acknowledges the World Data Center for Geomagnetism, Kyoto, for providing the geomagnetic data, the National Oceanic and Atmospheric Administration (NOAA) for the GOES solar flare data, and the Crustal Dynamics Data Information System (CDDIS) for providing the TEC data. The author Nagaraja expresses gratitude to the Inter-University Centre for Astronomy and Astrophysics in Pune, India for their assistance in the form of an associate fellowship. 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V. 2000, “Ionospheric storm of early November 1993 in the Indian equatorial region”, Journal of Geophysical Research: Space Physics, 105(A8), 18443-18455 Sharma, S., Galav, P., Dashora, N., Alex, S., Dabas, R. S., & Pandey, R. 2011, “Response of low‐latitude ionospheric total electron content to the geomagnetic storm of 24 August 2005”, Journal of Geophysical Research: Space Physics, 116(A5) Singh, A., Rathore, V. S., Kumar, S., Rao, S. S., Singh, S. K., & Singh, A. K. 2021, “Effect of intense geomagnetic storms on low-latitude TEC during the ascending phase of the solar cycle 24”, Journal of Astrophysics and Astronomy, 42(2), 99 Sur, D., Firdaus, J., Dutta, R., Bhattacharyya, C., Banerjee, S., & Paul, T. 2020, “Response of Low Latitude Ionization Towards Intense Geomagnetic Storm in 2018”, Proceedings of Industry Interactive Innovations in Science, Engineering & Technology (I3SET2K19). Tsurutani, B. T., Judge, D. L., Guarnieri, F. L., Gangopadhyay, P., Jones, A. R., Nuttall, J., ... & Viereck, R. 2005, “The October 28, 2003 extreme EUV solar flare and resultant extreme ionospheric effects: Comparison to other Halloween events and the Bastille Day event”, Geophysical Research Letters, 32(3) Additional Declarations No competing interests reported. Cite Share Download PDF Status: Posted Version 1 posted You are reading this latest preprint version Research Square lets you share your work early, gain feedback from the community, and start making changes to your manuscript prior to peer review in a journal. As a division of Research Square Company, we’re committed to making research communication faster, fairer, and more useful. We do this by developing innovative software and high quality services for the global research community. Our growing team is made up of researchers and industry professionals working together to solve the most critical problems facing scientific publishing. Also discoverable on Platform About Our Team In Review Editorial Policies Advisory Board Help Center Resources Author Services Accessibility API Access RSS feed Manage Cookie Preferences © Research Square 2026 | ISSN 2693-5015 (online) Privacy Policy Terms of Service Do Not Sell My Personal Information {"props":{"pageProps":{"initialData":{"identity":"rs-4691095","acceptedTermsAndConditions":true,"allowDirectSubmit":true,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":329867065,"identity":"997eb1d3-a6c7-4fef-8893-da7784a37177","order_by":0,"name":"Chaithra P","email":"","orcid":"","institution":"Bangalore University","correspondingAuthor":false,"prefix":"","firstName":"Chaithra","middleName":"","lastName":"P","suffix":""},{"id":329867068,"identity":"a8e197c5-b459-41f3-9581-0946ec28e731","order_by":1,"name":"Kamsali Nagaraja","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAABCklEQVRIiWNgGAWjYBACCTBZIAHl8tgACcbGA4S1GMC1pIG0NBCjBc4/DCbxapFsP5384YeBRR5//+JnH37InLdb234YaEuNTTQuLdI8udskewwkiiVuPDOe2cNzO3nbmUSglmNpuQ04tMgx5G5j4DGQSGy4ccCYgQeoxewAUAtjw2HcWvjfbv74B6hl/o3jnxn/8JxLNjv/EL8WaYncDdIgWzac7zFm5uE5YGd2g4AtkjPebpOWAWrZeIOnmFmGJznB7AbQlgQ8fpE4n7v545uKusR5549vZnzbY2dvdj794YMPNTY4tSBpTgBGYg9DIlhlAkHlIMB/AEj8YLAnSvEoGAWjYBSMKAAAgb5kSdLMlfIAAAAASUVORK5CYII=","orcid":"","institution":"Bangalore University","correspondingAuthor":true,"prefix":"","firstName":"Kamsali","middleName":"","lastName":"Nagaraja","suffix":""}],"badges":[],"createdAt":"2024-07-05 09:13:08","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-4691095/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-4691095/v1","draftVersion":[],"editorialEvents":[],"editorialNote":"","failedWorkflow":false,"files":[{"id":61415964,"identity":"d31e348a-89b0-4f81-97d2-130c783ccbc3","added_by":"auto","created_at":"2024-07-30 12:44:46","extension":"png","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":157146,"visible":true,"origin":"","legend":"\u003cp\u003eSchematic representation of a GNSS receiver situated on Earth\u003c/p\u003e","description":"","filename":"floatimage1.png","url":"https://assets-eu.researchsquare.com/files/rs-4691095/v1/16ea8dd655aea44f0b155681.png"},{"id":61416501,"identity":"28826345-4ae1-4d33-96f7-85ecb9c02fd3","added_by":"auto","created_at":"2024-07-30 12:52:46","extension":"png","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":1077988,"visible":true,"origin":"","legend":"\u003cp\u003eDisturbed storm time (DST) index, Planetary- K (Kp) index and Ionospheric TEC variations from 09 to 13, May 2024.\u003c/p\u003e","description":"","filename":"floatimage2.png","url":"https://assets-eu.researchsquare.com/files/rs-4691095/v1/07a653ad69819e663d2b6c61.png"},{"id":61415961,"identity":"5d8e781b-da17-4c94-9a8e-7743abfa6188","added_by":"auto","created_at":"2024-07-30 12:44:45","extension":"png","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":829125,"visible":true,"origin":"","legend":"\u003cp\u003eSolar flare intensity (I), Ionospheric TEC variation over the stations IISC, POL2, and NOVM for the period from 9 to 13, May 2024.\u003c/p\u003e","description":"","filename":"floatimage3.png","url":"https://assets-eu.researchsquare.com/files/rs-4691095/v1/4c93cd418639a0ed3bec27be.png"},{"id":61415962,"identity":"582a5373-f0b8-4382-8e3f-0317ffe2bade","added_by":"auto","created_at":"2024-07-30 12:44:46","extension":"png","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":679453,"visible":true,"origin":"","legend":"\u003cp\u003eCorrelation between observed TEC with IRI-TEC during the geomagnetic storm\u003c/p\u003e","description":"","filename":"floatimage4.png","url":"https://assets-eu.researchsquare.com/files/rs-4691095/v1/be6c4eee3e82b5da68487fc1.png"},{"id":61930614,"identity":"73f5b61a-ab5a-4757-a255-51e0d88693fd","added_by":"auto","created_at":"2024-08-07 08:08:33","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":3678158,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-4691095/v1/13c2a225-95c7-46ff-b461-02a9380c65a3.pdf"}],"financialInterests":"No competing interests reported.","formattedTitle":"Ionospheric TEC variations during an intense geomagnetic storm on 11 May 2024","fulltext":[{"header":"1. Introduction","content":"\u003cp\u003eThe temporal and spatial variability of Earth\u0026rsquo;s ionosphere is significant in space weather. The variability is highly influenced by multiple strong coupling processes (Saranya et al., \u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e2015\u003c/span\u003e). Solar activity such as Coronal Mass Ejections (CMEs) and high-speed solar wind streams, interact with the Earth\u0026rsquo;s magnetosphere to cause geomagnetic storms. The interactions cause greater plasma circulation within the magnetosphere, resulting in high electric currents and fields (Gonzalez et al., \u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e1994\u003c/span\u003e). Storms have an impact on the Earth's ionosphere, causing fluctuations in Total Electron Content (TEC). TEC is an important indicator that quantifies the number of electrons inside a vertical column of the ionosphere, spanning from 50 km to 1000 km above the Earth\u0026rsquo;s surface (Bhattarai et al., \u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e2018\u003c/span\u003e) and 1 TEC unit\u0026thinsp;=\u0026thinsp;1\u0026times;10\u003csup\u003e16\u003c/sup\u003e electrons/m\u003csup\u003e2\u003c/sup\u003e. Significant information on the effects of space weather on satellite systems, communication, and navigation may be obtained by comprehending the latitudinal response of ionospheric thermoelectric conduction during geomagnetic storms (Kintner et al., 2007).\u003c/p\u003e \u003cp\u003eSpecific features of low-latitude and equatorial ionosphere include the electrodynamics of the plasma fountain, the equatorial electrojet (EEJ), the equatorial ionization anomaly (EIA), and the development of equatorial plasma bubbles after sunset (Panda et al., \u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e2013\u003c/span\u003e; Harsha et al., 2020; Ghanshyam et al., 2023). The EIA consists of two crests of increased TEC centered around \u0026plusmn;\u0026thinsp;15\u0026deg; magnetic latitude, separated by a trough along the magnetic equator (Appleton \u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e1946\u003c/span\u003e; Olwendo et al., \u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e2017\u003c/span\u003e; Ghanshyam et al., 2023). The equatorial plasma fountain phenomenon elevates ionospheric plasma to greater heights, resulting in its dispersion along magnetic field lines and the formation of crests (Anderson, \u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1981\u003c/span\u003e). The EIA results from the eastward electric fields that occur during daytime, which also contribute to the equatorial ionospheric fountain effect (Appleton, \u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e1946\u003c/span\u003e). This phenomenon is caused by an upward drift in E\u0026times;B a result of the interaction between the horizontal northward magnetic fields and the eastward electric fields near the equator. Panda et al. (\u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e2013\u003c/span\u003e) state that the plasma is elevated by a vertical movement and transported to greater altitudes. From there, it moves to higher latitudes via magnetic field lines. The plasma flow at magnetic latitudes\u0026thinsp;\u0026plusmn;\u0026thinsp;15\u0026deg; is responsible for the production of EIA peaks (Kelley, \u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e2009\u003c/span\u003e).\u003c/p\u003e \u003cp\u003eThe ionosphere receives a large amount of energy from powerful geomagnetic storms that occur at high latitudes. This energy is responsible for the production of currents, electric fields, and Joule heating. Disturbed winds and disturbance dynamo processes may have an impact on ionospheric electric currents and fields. These storms may disrupt the equatorial ionosphere by shifting electric fields from high to low latitudes (Sastri et al., \u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e2000\u003c/span\u003e). Storms cause two groups of electric fields. The first one is called the disturbance dynamo electric field (DDEF), which can persist for more than a day. It counteracts the normal zonal electric field during quiet periods and shifts westward during the day and eastward during the night. The second type is the transitory prompt penetration electric field (PPEF), generated by the solar wind's magnetospheric dynamo. This electric field moves westward at night and eastward during the day. This PPEF lasts only a few hours. That means that during a storm, the eastward electric field during the daytime can change, which can increase or decrease the plasma fountain effect (Lin et al., \u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e2007\u003c/span\u003e; Olwendo et al., \u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e2017\u003c/span\u003e).\u003c/p\u003e \u003cp\u003eMannucci et al. (\u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e2005\u003c/span\u003e) investigated the impact of a Halloween storm, with a disturbance storm time index (Dst) of -390 nT, on fluctuations in the total electron content of the ionosphere. The study showed that plasma transport towards the pole and potential uplift at mid-latitudes contribute to significant increase in mid-latitude plasma, which may lead to high TEC differences and TEC plumes resulting from subauroral electric fields. Sharma et al. (\u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e2011\u003c/span\u003e) conducted a study on the TEC of the ionosphere at low latitudes in response to a geomagnetic storm that occurred on August 25, 2005. The storm had a Dst value of -184 nT. During the storm, the TEC records a peak with two distinct humps, which have an amplitude about twice as large as that observed on a quiet day. The second peak belongs to the plasma fountain effect, whereas the first peak is assigned to the PPEF. In addition, it has been shown that the impact of the PPEF is nearly uniform in the longitudinal direction. Ikubanni et al. (\u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e2020\u003c/span\u003e) studied the impact of intense geomagnetic storms on TEC in the low-latitude area of Africa. March 17, 2013, geomagnetic storm (Dst = -132 nT) had a substantial influence at commencement of recovery phase, particularly at Equatorial Ionization Anomaly (EIA) crest site. On the other hand, March 17, 2015 storm (Dst = -234 nT) event had a significant impact near the end of the main phase and during recovery phase. VTEC reactions have been analysed during a geomagnetic storm (Dst = -175 nT) from August 24 to 31, 2018, and found that the VTEC peak on August 26, 2018 was produced by the PPEF from a geomagnetic storm (Sur et al. \u003cspan citationid=\"CR24\" class=\"CitationRef\"\u003e2020\u003c/span\u003e). The corresponding decrease in VTEC over the subsequent days was attributed to DDEF during the storm\u0026rsquo;s recovery phase. The impact of four strong geomagnetic storms that occurred between 2010 and 2015 on fluctuations in Total Electron Content (TEC) in low-latitude areas of India (Singh et al. \u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e2021\u003c/span\u003e). They found that the notable changes in TEC during the storm period were mostly attributed to the electric field and neutral winds associated with the storms.\u003c/p\u003e \u003cp\u003eGeomagnetic storms cause substantial fluctuations in the electron density of the ionosphere, which are often measured as total electron content (TEC). These storms induce ionospheric perturbations that may either increase or decrease electron density. This research investigates the variations in ionospheric TEC at various locations across the planet Earth during the May 11, 2024, which is the most severe (Dst = -412 nT) to be observed after the Halloween storm that occurred on October 29\u0026ndash;30, 2003 (Dst = -390 nT).\u003c/p\u003e"},{"header":"2. Data and method of analysis","content":"\u003cp\u003e \u003cdiv class=\"BlockQuote\"\u003e \u003cp\u003eThis research analyzes data from three distinct geographic sites, namely IISC (13.02\u0026deg;N, 77.57\u0026deg;E), POL2 (42.68\u0026deg;N, 74.69\u0026deg;E), and NOVM (55.03\u0026deg;N, 82.91\u0026deg;E), to examine the latitudinal reaction of ionospheric TEC during the geomagnetic storms. These stations are situated in latitudes ranging from low to mid, which enables a thorough investigation of the impact of the geomagnetic storm across different latitudes. The selection of GPS stations in this study was based on their geographical and geomagnetic coordinates, which are shown in Table-1. The IISC is situated inside the EIA area, although the stations POL2 and NOVM are located outside of it. Ionospheric TEC data is obtained by obtaining the RINEX file from the International GNSS Station (IGS), which may be accessed at the following link: \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://cddis.nasa.gov/Data_and_Derived_Products/GNSS/broadcast_ephemeris_data.html\u003c/span\u003e\u003cspan address=\"https://cddis.nasa.gov/Data_and_Derived_Products/GNSS/broadcast_ephemeris_data.html\" targettype=\"URL\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e. Gopi Seemala\u0026rsquo;s GPS-TEC software package is used to process this data. Reddybattula et al. (\u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e2019\u003c/span\u003e) provide a comprehensive elucidation of the operational basis of the program. Figure\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e displays the several sites of the IGS network on the Earth\u0026rsquo;s surface that were chosen for this study.\u003c/p\u003e \u003c/div\u003e \u003c/p\u003e \u003cp\u003eTable-1: GPS stations with geographic and geomagnetic coordinates used in the study\u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"No\" id=\"Taba\" border=\"1\"\u003e \u003ccolgroup cols=\"5\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003eStation code\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colspan=\"2\" nameend=\"c3\" namest=\"c2\"\u003e \u003cp\u003eGeographic coordinates\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colspan=\"2\" nameend=\"c5\" namest=\"c4\"\u003e \u003cp\u003eGeomagnetic coordinates\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eLatitude\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003eLongitude\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003eLatitude\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c5\"\u003e \u003cp\u003eLongitude\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eNOVM\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e55.03 N\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e82.91 E\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e46.31 N\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e159.81 E\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003ePOL2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e42.68 N\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e74.69 E\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e34.55 N\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e151.09 E\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eIISC\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e13.02 N\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e77.57 E\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e4.90 N\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e150.93 E\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003cp\u003e \u003cdiv class=\"BlockQuote\"\u003e \u003cp\u003eThe disturbed storm time (Dst) index is used to measure the intensity of a geomagnetic storm. The geomagnetic storms are categorised as moderate (-50 nT\u0026thinsp;\u0026ge;\u0026thinsp;Dst \u0026gt; -100 nT), strong (-100 nT\u0026thinsp;\u0026ge;\u0026thinsp;Dst \u0026gt; -200 nT), and extreme (-200 nT\u0026thinsp;\u0026ge;\u0026thinsp;Dst) based on higher deviation of Dst index from undisturbed duration (Gonzalez et al., \u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e1994\u003c/span\u003e). Gosling et al. (\u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e1991\u003c/span\u003e) classified geomagnetic storms into several categories based on the Kp index of 3-hour values. These categories include weak (Kp\u0026thinsp;\u0026le;\u0026thinsp;5), moderate (Kp\u0026thinsp;=\u0026thinsp;6), strong (Kp\u0026thinsp;=\u0026thinsp;7), and severe storms (Kp\u0026thinsp;\u0026ge;\u0026thinsp;8). The Dst and Kp indices data were obtained from Kyoto Geomagnetic Data Service via \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://wdc.kugi.kyoto-u.ac.jp/wdc/Sec3.html\u003c/span\u003e\u003cspan address=\"https://wdc.kugi.kyoto-u.ac.jp/wdc/Sec3.html\" targettype=\"URL\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e. Intensity of solar flare data was retrieved from the National Oceanic and Atmospheric Administration (NOAA) through \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://www.swpc.noaa.gov/products/goes-x-ray-flux\u003c/span\u003e\u003cspan address=\"https://www.swpc.noaa.gov/products/goes-x-ray-flux\" targettype=\"URL\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e. The NOAA/GOES XRS classifies solar flare intensities, which spans a wide range, on their peak emissions in soft x-ray (0.1\u0026ndash;0.8 nm) spectral region. The solar flares are classified as A-class begins at 10\u003csup\u003e\u0026minus;\u0026thinsp;8\u003c/sup\u003e Wm\u003csup\u003e-2\u003c/sup\u003e as the initial x-ray flux level, B-class (\u0026ge;\u0026thinsp;10\u003csup\u003e\u0026minus;\u0026thinsp;7\u003c/sup\u003e Wm\u003csup\u003e-2\u003c/sup\u003e), C- class (10\u003csup\u003e\u0026minus;\u0026thinsp;6\u003c/sup\u003e Wm-\u003csup\u003e2\u003c/sup\u003e), M-class (10\u003csup\u003e\u0026minus;\u0026thinsp;5\u003c/sup\u003e Wm-\u003csup\u003e2\u003c/sup\u003e), and X-class (10\u003csup\u003e\u0026minus;\u0026thinsp;4\u003c/sup\u003e Wm-\u003csup\u003e2\u003c/sup\u003e) flares. TEC data obtained is compared with the TEC data predicted by the IRI-2021 model throughout a geomagnetic storm.\u003c/p\u003e \u003c/div\u003e \u003c/p\u003e"},{"header":"3. Results and Discussions","content":"\u003cp\u003e \u003cdiv class=\"BlockQuote\"\u003e \u003cp\u003eAn analysis was conducted on the Ionospheric TEC observations obtained from three GNSS receiver stations, namely IISC, POL2, and NOVM. The observations were made over five days during May 09\u0026ndash;13, 2024, encompassing the day before, during, and after a geomagnetic storm. A substantial decrease in the Dst index, which quantifies the disturbance in the Earth's magnetic field, indicated the beginning of a severe storm. During the present observation period, the Dst index attained a value of -413 nT, indicating an intense geomagnetic storm. The significant level of geomagnetic activity was further validated by the Kp index attaining a value of 9, which quantifies geomagnetic activity on a scale ranging from 0 to 9. The measurements demonstrated the storm's intensity and the possibility of significant disruptions in the ionosphere.\u003c/p\u003e \u003cp\u003eThe TEC fluctuations over the three selected areas during the geomagnetic storm are depicted in Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003e, together with the accompanying Dst and Kp index. The duration of the geomagnetic storm was about 24 hours, as seen by the darkened region in Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003e. The Sudden Commencement of Storm (SCS) begins at 18:00 UT on May 10, 2024. The TEC values for the three sites show typical diurnal variations, with higher values during the daytime and lower values at nighttime. After SCS, the highest TEC recorded at the IISC station on May 11, 2024 was 96.16 TECU, which was notably higher than the values recorded from the previous days. The equatorial plasma fountain effect and the equatorial ionization anomaly (EIA) are responsible for an increase in TEC at IISC. The eastward electric field at the equator can be strengthened by penetration of electric fields from high latitudes during geomagnetic storms. Stronger E\u0026times;B drift that raises the altitude of the ionospheric plasma, and from there, it diffuses along magnetic field lines forces to generate enhanced EIA crests (Fejer et al., \u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e1999\u003c/span\u003e). Prompt Penetration Electric Fields (PPEFs) can also quickly reach the equator during intense storms, enhancing the EIA and increases the ionospheric TEC (Panda et al., \u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e2015\u003c/span\u003e).\u003c/p\u003e \u003cp\u003eThe study demonstrates that there was a substantial decrease in Total Electron Content (TEC) measurements over the POL2 station during the geomagnetic storm. The highest TEC recorded on May 11, 2024 is 18.08 TECU, indicating a significant 59% reduction compared to preceding days characterized by minimal storm activity. The decrease in TEC at POL2 is primarily due to the intricate interplay between electric fields and thermospheric winds during the storm. Mid-latitude regions often experience the combined impacts of direct electric field penetration from higher latitudes and disturbance dynamo phenomena. The PPEFs initially cause a rapid rise in Total Electron Content. However, the ensuing disturbance dynamo generates westward electric fields during the daylight, which counteract the upward E\u0026times;B drift and result in decreased TEC (Maruyama et al., \u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e2005\u003c/span\u003e).\u003c/p\u003e \u003c/div\u003e \u003c/p\u003e \u003cp\u003eOver NOVM location, the maximum TEC observed during geomagnetic storm on May 11, 2024 is 17.57 TECU, representing a 36% decrease in TEC compared to the previous days. Several high-latitude effects are responsible for the drop in TEC at NOVM, even though it is at the end of mid-latitudes. Auroral precipitation and electric fields at high latitudes may exert significant impacts. During geomagnetic storms, the auroral oval expands, leading to the precipitation of energetic particles into the ionosphere and an increase in ionization in the E-region. This leads to an elevation in recombination rates, resulting in a decrease in total electron content (TEC) in the F-region. Intense Joule heating may also cause the upward movement of neutral gas, leading to increased recombination rates and further reduction of Total Electron Content (TEC) at high altitudes (Fuller-Rowell et al., \u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e1994\u003c/span\u003e).\u003c/p\u003e \u003cp\u003e \u003cdiv class=\"BlockQuote\"\u003e \u003cp\u003eOn May 11, 2024, a noticeable solar flare was also observed in addition to the geomagnetic storm. The solar flare was categorized as an X-class solar flare, signifying a very strong flare with the Intensity of the solar flare as 5.89\u0026times;10\u003csup\u003e\u0026minus;\u0026thinsp;4\u003c/sup\u003e Wm\u003csup\u003e-2\u003c/sup\u003e. The Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003e shows the changes in the ionospheric TEC over the three stations chosen during extreme solar flare events. Solar flares are sudden and massive bursts of radiation from the sun that can produce significant changes in ionization within the Earth\u0026rsquo;s ionosphere.\u003c/p\u003e \u003c/div\u003e \u003c/p\u003e \u003cp\u003e \u003cdiv class=\"BlockQuote\"\u003e \u003cp\u003eThe fluctuations in the TEC over the selected three sites can be attributed to several causes including geomagnetic storm dynamics, ionospheric processes at various latitudes, and the impact of the X- class solar flares. The X\u003csub\u003e5.89\u003c/sub\u003e solar flare would have caused more ionization in the lower ionosphere, resulting in higher TEC values. Solar flares produce large quantities of X-rays and Extreme Ultra Violet (EUV) radiation, which substantially boosts ionization rates (Tsurutani et al., \u003cspan citationid=\"CR25\" class=\"CitationRef\"\u003e2005\u003c/span\u003e). Further increased in the ionization along with geomagnetic storm effects would account for the increase in TEC over IISC. The X\u003csub\u003e5.89\u003c/sub\u003e solar flare caused considerable changes in TEC values, which were especially noticeable over POL2 and NOVM due to the high latitude\u0026rsquo;s sensitivity to geomagnetic disturbances and ionospheric coupling. The solar flare has led to an increase in ionization, which, when paired with the effects of geomagnetic storms, has created a notable initial rise in Total Electron Content. This increase is then followed by a sharp decrease owing to accelerated recombination and particle precipitation.\u003c/p\u003e \u003cp\u003eThe IRI-2020 (International Reference Ionosphere) model was used to investigate the ionosphere and assess the accuracy of our observed Total Electron Content (TEC) data, as seen in Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003e, during the period of geomagnetic storm activity. The correlation coefficients (R\u0026sup2;) were calculated to assess the relationship between the modelled and observed TEC values at all stations. The found correlation coefficients (R\u0026sup2;) are as follows: R\u0026sup2; = 0.80 for IISC, R\u0026sup2; = 0.57 for POL2, and R\u0026sup2; = 0.84 for NOVM. The correlations indicate a substantial concurrence between the observed and predicted TEC values at IISC and NOVM, whereas a modest correlation is reported at POL2. The IRI-2020 model demonstrates a robust connection at IISC and NOVM, suggesting its efficacy in accurately modeling the ionospheric behavior at lower and higher latitudes during periods of disturbance. The intricate behavior of the ionosphere at mid-latitudes during geomagnetic storms may not be fully represented by the model, as seen by the moderate correlation with the IRI-2020 model, indicating the presence of some discrepancies.\u003c/p\u003e \u003c/div\u003e \u003c/p\u003e \u003cp\u003e \u003c/p\u003e"},{"header":"4. Conclusion","content":"\u003cp\u003e \u003cdiv class=\"BlockQuote\"\u003e \u003cp\u003eThe analysis of Total Electron Content (TEC) changes during an intense geomagnetic storm on May 11, 2024 reveals significant differences in ionospheric responses across various latitudes. The recorded TEC data was affected by both the geomagnetic storm and an X-class solar flare. At the low-latitude station IISC, the TEC data increased, whereas at the mid-latitudes POL2 and NOVM locations, it decreased. Disparities in the impact of the solar flare on TEC were observed based on latitude, namely at the NOVM, POL2, and IISC stations. The differing ionospheric response to the enhanced radiation and subsequent impacts of geomagnetic storms can account for this variance. The TEC values experienced a significant increase above the IISC during the storm that can be attributed to the equatorial plasma fountain effect and the equatorial ionization anomaly. The X\u003csub\u003e5.89\u003c/sub\u003e solar flare contributed to increased ionization, which led to higher TEC values. TEC values at POL2 decreased sharply throughout the storm, owing to complicated interactions between storm-time electric fields and thermospheric winds. A significant drop in TEC was found at NOVM, owing to high-latitude factors such as auroral precipitation and increased recombination rates caused by intense Joule heating. To minimize the effect of space weather on communication and navigation networks that rely on satellites, this research provides helpful information for enhancing ionospheric models and prediction tools.\u003c/p\u003e \u003c/div\u003e \u003c/p\u003e"},{"header":"Declarations","content":"\u003ch2\u003eAuthor Contribution\u003c/h2\u003e\u003cp\u003eThe research was carried out jointly with shared responsibilities, and both authors contributed to the manuscript. Chaithra P and Kamsali Nagaraja worked together to develop the concept, methodology, and formal analysis and conducted the investigation. Chaithra P and Kamsali Nagaraja were also involved in the initial drafting, revision, and editing of the manuscript in its entirety. Kamsali Nagaraja served as superviser for the research work and handled the resources.\u003c/p\u003e\u003ch2\u003eAcknowledgments\u003c/h2\u003e \u003cp\u003eThe author acknowledges the World Data Center for Geomagnetism, Kyoto, for providing the geomagnetic data, the National Oceanic and Atmospheric Administration (NOAA) for the GOES solar flare data, and the Crustal Dynamics Data Information System (CDDIS) for providing the TEC data. The author Nagaraja expresses gratitude to the Inter-University Centre for Astronomy and Astrophysics in Pune, India for their assistance in the form of an associate fellowship.\u003c/p\u003e\u003ch2\u003eData Availability\u003c/h2\u003e \u003cp\u003eIonospheric is obtained from the International GNSS Station (IGS) with link: \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://cddis.nasa.gov/Data_and_Derived_Products/GNSS/broadcast_ephemeris_data.html\u003c/span\u003e\u003cspan address=\"https://cddis.nasa.gov/Data_and_Derived_Products/GNSS/broadcast_ephemeris_data.html\" targettype=\"URL\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e. The Dst and Kp indices data were obtained from Kyoto Geomagnetic Data Service via \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://wdc.kugi.kyoto-u.ac.jp/wdc/Sec3.html\u003c/span\u003e\u003cspan address=\"https://wdc.kugi.kyoto-u.ac.jp/wdc/Sec3.html\" targettype=\"URL\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e Intensity of solar flare data was retrieved from the National Oceanic and Atmospheric Administration (NOAA) through \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://www.swpc.noaa.gov/products/goes-x-ray-flux\u003c/span\u003e\u003cspan address=\"https://www.swpc.noaa.gov/products/goes-x-ray-flux\" targettype=\"URL\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\n \u003cli\u003eAnderson, D. 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K. 2021, \u0026ldquo;Effect of intense geomagnetic storms on low-latitude TEC during the ascending phase of the solar cycle 24\u0026rdquo;, Journal of Astrophysics and Astronomy, 42(2), 99\u0026nbsp;\u003c/li\u003e\n \u003cli\u003eSur, D., Firdaus, J., Dutta, R., Bhattacharyya, C., Banerjee, S., \u0026amp; Paul, T. 2020, \u0026ldquo;Response of Low Latitude Ionization Towards Intense Geomagnetic Storm in 2018\u0026rdquo;, Proceedings of Industry Interactive Innovations in Science, Engineering \u0026amp; Technology (I3SET2K19).\u003c/li\u003e\n \u003cli\u003eTsurutani, B. T., Judge, D. L., Guarnieri, F. L., Gangopadhyay, P., Jones, A. R., Nuttall, J., ... \u0026amp; Viereck, R. 2005, \u0026ldquo;The October 28, 2003 extreme EUV solar flare and resultant extreme ionospheric effects: Comparison to other Halloween events and the Bastille Day event\u0026rdquo;, Geophysical Research Letters, 32(3)\u003c/li\u003e\n\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":true,"highlight":"","institution":"","isAcceptedByJournal":false,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true},"keywords":"Ionosphere, TEC, Earth, Sun, Geomagnetic Storm, Solar flare","lastPublishedDoi":"10.21203/rs.3.rs-4691095/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-4691095/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eOn May 11, 2024, a severe geomagnetic storm occurred, causing significant disruptions to Earth\u0026rsquo;s magnetosphere and ionosphere. These storms, primarily caused by solar activity, are distinguished by variations in solar wind that increase energy flow from the Sun to Earth. The present research aims to analyze the latitudinal response of ionospheric Total Electron Content (TEC) during this event. The analysis is based on data collected from three different geographic locations: IISC (13.02\u0026deg;N, 77.57\u0026deg;E), POL2 (42.68\u0026deg;N, 74.69\u0026deg;E), and NOVM (55.03\u0026deg;N, 82.91\u0026deg;E). The electron density of the ionosphere is crucial for satellite-based communication and navigation systems. Geomagnetic storm strength is measured by the Kp-index and Disturbance storm time (Dst) index. During a geomagnetic storm and X-class flare of magnitude 5.89, a maximum Dst index of -412 nT and Kp index of 9 are observed during the storm day. TEC values increased at IISc during the storm period compared to quiet days, but decreased over POL2 and NOVM stations. A good correlation was observed between the observed TEC during a storm day and the predicted TEC by the IRI-2020 model over IISC and NOVM, while moderate correlation was observed over POL2.\u003c/p\u003e","manuscriptTitle":"Ionospheric TEC variations during an intense geomagnetic storm on 11 May 2024","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2024-07-30 12:44:41","doi":"10.21203/rs.3.rs-4691095/v1","editorialEvents":[{"type":"communityComments","content":0}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"4147684e-bd7a-4316-ad7a-0283cb97272b","owner":[],"postedDate":"July 30th, 2024","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"posted","subjectAreas":[],"tags":[],"updatedAt":"2024-08-07T08:00:04+00:00","versionOfRecord":[],"versionCreatedAt":"2024-07-30 12:44:41","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-4691095","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-4691095","identity":"rs-4691095","version":["v1"]},"buildId":"8U1c8b4HqxoKbykW_rLl7","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}