Characteristics of Magnetic Field Evolution and Onset Process of Successive X-class Flares in May 2024

Characteristics of Magnetic Field Evolution and Onset Process of Successive X-class Flares in 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 Characteristics of Magnetic Field Evolution and Onset Process of Successive X-class Flares in May 2024 Yumi Bamba, Daikou Shiota, Kanya Kusano This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-7986926/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 In early May 2024, active regions (ARs) 13663 and 13664 appeared on the solar disk and produced 17 X-class flares. The associated coronal mass ejections caused geomagnetic disturbances, named the Gannon Storm, resulting in significant societal impacts. To investigate why these regions generated successive X-class flares, we conducted detailed analyses of nine X-class flares that occurred near the solar disk center using data from the Solar Dynamics Observatory and post-event analysis based on the κ-scheme, a flare prediction scheme utilizing nonlinear force-free field modeling. Comparative analysis was also performed with ARs 12192 and 12673, which produced multiple X-class flares during the previous solar cycle 24. Our analysis showed that AR 13664 maintained flare-favorable conditions through the emergence of multiple twisted magnetic flux systems and sustained flux injection over 11 days, which continuously increased the releasable magnetic energy (Er) and preserved small critical radii (rc) conducive flare onset reconnection. AR 13663 also produced multiple flares due to strong magnetic shear and a rapid flux injection episode lasting 2.5 days, which led to the rapid growth of flare-triggering magnetic structures. All nine flares originated under the conditions of rc 1.9x1030 [erg], which we propose as new threshold values for X-class flare prediction using the κ-scheme. Additionally, some flares were triggered by small-scale reconnection outside strong shear regions, propagating along the magnetic polarity inversion line like a fuse and activating larger energy release. These findings highlight the importance of monitoring both strong and weak shear regions for effective flare forecasting. This study demonstrates the potential to contribute to the development of a preemptive and stepwise warning system for large flares based on the κ-scheme, by enabling future statistical analyses of a broader set of events—including M-class flares—to derive threshold values corresponding to flare magnitudes. Sun Sunspot Solar magnetic field Solar flare Flare prediction Space weather Full Text Supplementary Files graphicabstract.png 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-7986926","acceptedTermsAndConditions":true,"allowDirectSubmit":true,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":543992211,"identity":"343755db-a08b-44a6-a64c-9af020632369","order_by":0,"name":"Yumi 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The associated coronal mass ejections caused geomagnetic disturbances, named the Gannon Storm, resulting in significant societal impacts. To investigate why these regions generated successive X-class flares, we conducted detailed analyses of nine X-class flares that occurred near the solar disk center using data from the Solar Dynamics Observatory and post-event analysis based on the κ-scheme, a flare prediction scheme utilizing nonlinear force-free field modeling. Comparative analysis was also performed with ARs 12192 and 12673, which produced multiple X-class flares during the previous solar cycle 24. Our analysis showed that AR 13664 maintained flare-favorable conditions through the emergence of multiple twisted magnetic flux systems and sustained flux injection over 11 days, which continuously increased the releasable magnetic energy (Er) and preserved small critical radii (rc) conducive flare onset reconnection. AR 13663 also produced multiple flares due to strong magnetic shear and a rapid flux injection episode lasting 2.5 days, which led to the rapid growth of flare-triggering magnetic structures. All nine flares originated under the conditions of rc \u0026lt; 1.1 [Mm] and Er \u0026gt; 1.9x1030 [erg], which we propose as new threshold values for X-class flare prediction using the κ-scheme. Additionally, some flares were triggered by small-scale reconnection outside strong shear regions, propagating along the magnetic polarity inversion line like a fuse and activating larger energy release. These findings highlight the importance of monitoring both strong and weak shear regions for effective flare forecasting. 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