Detection of ``diffuse'' coronal He I1083 during the April 8 2024 Solar Eclipse: evidence for terrestrial atmospheric scattering contribution

Detection of ``diffuse'' coronal He I1083 during the April 8 2024 Solar Eclipse: evidence for terrestrial atmospheric scattering contribution | 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 Systematic Review Detection of ``diffuse'' coronal He I1083 during the April 8 2024 Solar Eclipse: evidence for terrestrial atmospheric scattering contribution Momchil Molnar, Roberto Casini, Paul Bryans, Ben Berkey, Kalista Tyson This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-5743793/v1 This work is licensed under a CC BY 4.0 License Status: Published Journal Publication published 27 Jun, 2025 Read the published version in Solar Physics → Version 1 posted 4 You are reading this latest preprint version Abstract Strong He I 1083 nm atomic line signals have previously been measured during total solar eclipses at coronal heights above the lunar limb. Theserather unexpected measurements have kindled a discussion about the suggested presence of significant amounts of neutral helium at coronal conditions.We performed spectroscopic observations of the He I 1083 nm wavelength regionduring the April 8th 2024 totalsolar eclipse, using an instrument specifically designed to test the presence of He I 1083 in the solar corona.We were able to detect the He I 1083 line, the forbidden coronal line of Fe XIII at 1074.7 nm, as well as thechromospheric H I 1093.8 nm (Paschen-gamma) line in our data.The chromospheric He I 1083 nm and H I 1093.8 nm lines were detected in both the corona and on the lunar disc. We hypothesize that our observations support a terrestrial atmospheric scattering of the solar flash spectrum as the origin of the He I 1083 signal during the April 8th 2024 eclipse. Our findings challenge the notion of abundant neutral helium in the solar corona suggested by previous eclipse observations. Corona Structures Eclipse Observations Spectral Line Intensity and Diagnostics Full Text Additional Declarations No competing interests reported. Cite Share Download PDF Status: Published Journal Publication published 27 Jun, 2025 Read the published version in Solar Physics → Version 1 posted Reviewers agreed at journal 25 Apr, 2025 Reviewers invited by journal 24 Apr, 2025 Submission checks completed at journal 15 Apr, 2025 First submitted to journal 04 Apr, 2025 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. 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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-5743793","acceptedTermsAndConditions":true,"allowDirectSubmit":false,"archivedVersions":[],"articleType":"Systematic Review","associatedPublications":[],"authors":[{"id":448173413,"identity":"b5c3b45f-b680-4f7e-9612-05208719d259","order_by":0,"name":"Momchil Molnar","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAAA2klEQVRIiWNgGAWjYJACZgYDCxDVACRsgJixgRgtEjCVacRqYYBrOUzYUbrt3YmfCwokgIzGtgc/95y3N7h9uIHh455anFrMzpzdLD0D6DCzMwfbDXue3U7ccC6xgXHGs+O4tdzI3cbMA9JyI7FNgufA7QSzM4wNzDwHjhGnRfLPgXP2pGmR5jlwgHEbREsNfr8AtfAA/dImLXMgOXE/UMvBGQcO4NZyvHfjZ54/NnJmx5uPSb45YGcv2cP+8MGHA3U4tcAADwrvAFERhA4I2zIKRsEoGAUjBgAA3yZYrhYFsjwAAAAASUVORK5CYII=","orcid":"","institution":"National Center for Atmospheric Research","correspondingAuthor":true,"prefix":"","firstName":"Momchil","middleName":"","lastName":"Molnar","suffix":""},{"id":448173414,"identity":"15c5ee0d-4273-49ba-a2f5-875002000182","order_by":1,"name":"Roberto Casini","email":"","orcid":"","institution":"National Center for Atmospheric Research","correspondingAuthor":false,"prefix":"","firstName":"Roberto","middleName":"","lastName":"Casini","suffix":""},{"id":448173416,"identity":"531c4d5a-1824-420f-afe2-01b96cc03c95","order_by":2,"name":"Paul Bryans","email":"","orcid":"","institution":"National Center for Atmospheric Research","correspondingAuthor":false,"prefix":"","firstName":"Paul","middleName":"","lastName":"Bryans","suffix":""},{"id":448173418,"identity":"91eb0aed-6997-46e2-87f2-05a9179d8938","order_by":3,"name":"Ben Berkey","email":"","orcid":"","institution":"National Center for Atmospheric Research","correspondingAuthor":false,"prefix":"","firstName":"Ben","middleName":"","lastName":"Berkey","suffix":""},{"id":448173419,"identity":"4a3dec8a-61e3-4556-9531-2f03e5095a41","order_by":4,"name":"Kalista Tyson","email":"","orcid":"","institution":"National Center for Atmospheric Research","correspondingAuthor":false,"prefix":"","firstName":"Kalista","middleName":"","lastName":"Tyson","suffix":""}],"badges":[],"createdAt":"2024-12-31 20:53:08","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-5743793/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-5743793/v1","draftVersion":[],"editorialEvents":[{"content":"https://doi.org/10.1007/s11207-025-02500-5","type":"published","date":"2025-06-27T15:57:16+00:00"}],"editorialNote":"","failedWorkflow":false,"files":[{"id":85686153,"identity":"f993fedd-cdf6-4046-8308-280d13af28a1","added_by":"auto","created_at":"2025-06-30 16:03:58","extension":"pdf","order_by":1,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":1962545,"visible":true,"origin":"","legend":"","description":"","filename":"CHEESEexperiment.pdf","url":"https://assets-eu.researchsquare.com/files/rs-5743793/v1_covered_d0886843-d300-4ed2-af16-b07e60ce010c.pdf"}],"financialInterests":"No competing interests reported.","formattedTitle":"Detection of ``diffuse'' coronal He I1083 during the April 8 2024 Solar Eclipse: evidence for terrestrial atmospheric scattering contribution","fulltext":[],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":false,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":false,"highlight":"","institution":"","isAcceptedByJournal":true,"isAuthorSuppliedPdf":true,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":true,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"solar-physics","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"sola","sideBox":"Learn more about [Solar Physics](http://link.springer.com/journal/11207)","snPcode":"11207","submissionUrl":"https://submission.nature.com/new-submission/11207/3","title":"Solar Physics","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"em","reportingPortfolio":"Springer Hybrid","inReviewEnabled":true,"inReviewRevisionsEnabled":false},"keywords":"Corona, Structures; Eclipse Observations; Spectral Line, Intensity and Diagnostics","lastPublishedDoi":"10.21203/rs.3.rs-5743793/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-5743793/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"Strong He I 1083 nm atomic line signals have previously been measured during total solar eclipses at coronal heights above the lunar limb. 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