{"id":"pod_polito_vanessa_2024-10-23T00:04:39.105Z","submitter":"","author":"Juraj Lörinčík[1,2], Jaroslav Dudík [3], Alberto Sainz Dalda [1, 2], Guillaume Aulanier [5,6,7], Vanessa Polito [2, 4], Bart De Pontieu [2,6,7] [1] Bay Area Environmental Research Institute [2] Lockheed Martin Solar & Astrophysics Laboratory [3] Astronomical Institute of the Czech Academy of Sciences [4] Department of Physics, Oregon State University [5] Sorbonne Université, Observatoire de Paris - PSL, École Polytechnique, Institut Polytechnique de Paris, CNRS, LPP [6] Rosseland Center for Solar Physics, University of Oslo [7] Institute of Theoretical Astrophysics, University of Oslo","status":"published","creation-date":"2024-10-23T00:04:39.157Z","last-modified-date":"2024-10-31T13:31:52.544Z","credit":"Juraj Lörinčík","title":"Observational discovery of super-Alfvénic slippage of reconnecting magnetic field lines","contentBlocks":[{"type":"text","text":"The%20morphology%20and%20dynamics%20of%20solar%20flare%20ribbons%20provides%20a%20wealth%20of%20information%20on%20magnetic%20reconnection%20driving%20solar%20flares.%20Flare%20kernels%20%28see%20e.g.%2C%20Fletcher%20et%20al.%202004%29%2C%20the%20building%20bricks%20of%20ribbons%2C%20are%20often%20seen%20to%20exhibit%20apparent%20motions%20along%20the%20ribbons%2C%20a%20signature%20of%20magnetic%20slipping%20reconnection%2C%20first%20noted%20by%20Dud%26iacute%3Bk%20et%20al.%20%282014%29.%20The%20observed%20slipping%20speeds%20are%20however%20usually%20by%20at%20least%20an%20order%20of%20magnitude%20lower%20than%20those%20predicted%20by%20numerical%20simulations.%20Super-Alfv%26eacute%3Bnic%20field%20line%20slippage%20at%20speeds%20exceeding%20thousands%20of%20kilometers%20per%20second%20is%20a%20key%20characteristic%20of%20%E2%80%98slip-running%20reconnection%E2%80%99%20%28Aulanier%20et%20al.%202006%2C%20Janvier%20et%20al.%202013%29."},{"type":"image","file":"","url":"nuggetvideos/2024/10/23/pod_polito_vanessa_2024-10-23T00%3A04%3A39.105Z/Fig1.png","hash":"a8039fa84db853c9041628d8fa66519f","mimeType":"image/png","caption":"Figure%201%3A%20SDO%2FAIA%20131%20%28left%29%20and%20304%20%28middle%29%20context%20observations%20of%20flare%20loops%20and%20ribbons%20after%20the%20flare%20onset.%20Panel%20on%20the%20right%20presents%20the%20IRIS%2FSJI%201330%20observations%20of%20the%20W%20ribbon.%20The%20red%20curve%20designates%20the%20artificial%20cut%20used%20to%20produce%20the%20stackplots."},{"type":"text","text":"Our%20new%20study%20%28L%26ouml%3Brin%C4%8D%26iacute%3Bk%20et%20al.%202024%29%20presents%20an%20analysis%20of%20IRIS%2FSJI%20observations%20of%20a%20confined%20C-class%20flare%20from%202022%20September%2025%20%28Figure%201%29.%20The%20SJI%201330%26Aring%3B%20channel%20imagery%2C%20dominated%20by%20chromospheric%20and%20transition%20region%20C%20II%20emission%2C%20captured%20the%20evolution%20of%20the%20W%20ribbon%20at%20a%20high%20cadence%20of%20less%20than%202%20seconds.%20The%20ribbon%20was%20composed%20of%20numerous%20fast-moving%20kernels%20whose%20dynamics%20was%20studied%20via%20a%20stackplot%20%28Figure%202%29%20constructed%20along%20the%20red%20cut%20indicated%20in%20the%20right%20panel%20of%20Figure%201.%20The%20kernel%20motions%20there%20imprint%20elongated%20traces%2C%20whose%20inclination%20is%20proportional%20to%20the%20kernel%20slipping%20speed.%20Many%20of%20the%20kernels%20were%20faint.%20In%20order%20to%20highlight%20their%20traces%2C%20the%20SJI%20observations%20were%20processed%20using%20the%20log-running%20ratio%20%28LRR%29%20technique%2C%20facilitating%20the%20measurements%20of%20kernel%20velocities.%20Linear%20fits%20to%20the%20kernel%20traces%20%28colored%20lines%20in%20Figure%202%29%20indicate%20a%20broad%20range%20of%20slipping%20velocities%2C%20ranging%20roughly%20between%20100%20and%202600%20km%2Fs.%20Multiple%20kernels%20exhibited%20speeds%20of%20the%20order%20of%201000%20km%2Fs%2C%20corresponding%20to%20the%20typical%20Alfv%26eacute%3Bn%20speeds%20in%20the%20solar%20corona%2C%20a%20direct%20observational%20evidence%20of%20slip-running%20reconnection."},{"type":"image","file":"","url":"nuggetvideos/2024/10/23/pod_polito_vanessa_2024-10-23T00%3A04%3A39.105Z/Fig2.png","hash":"ebafc5c173d6e93721f31bddea5ab703","mimeType":"image/png","caption":"Figure%202%3A%20Panel%20A%20presents%20the%20stackplot%20produced%20along%20the%20artificial%20cut%20plotted%20in%20Figure%201.%20Panels%20B%20and%20C%20present%20the%20same%20diagram%2C%20but%20produced%20using%20the%20LRR%20data%20and%20split%20to%20two%20time%20ranges%20with%20different%20saturation.%20The%20yellow%20and%20blue%20dotted%20lines%20designate%20linear%20fits%20to%20example%20traces%20of%20the%20slipping%20kernels."},{"type":"text","text":"This%20discovery%20has%20another%20implication%20for%20the%20understanding%20of%20magnetic%20reconnection%20in%20three%20dimensions.%20The%20observed%20ribbons%20exhibited%20only%20negligible%20separation%20motions%20%28see%20e.g.%2C%20Qiu%20et%20al.%202004%29%20at%20speeds%20below%205%20km%2Fs.%20As%20derived%20by%20Janvier%20et%20al.%20%282013%29%20and%20demonstrated%20Dud%26iacute%3Bk%20et%20al.%20%282016%29%2C%20the%20ratio%20of%20the%20slipping%20and%20separation%20speeds%20can%20be%20used%20as%20a%20proxy%20of%20the%20mapping%20norm%20N%20of%20field%20line%20connectivity.%20Our%20observations%20indicate%20N%20%26gt%3B%20500%2C%20representative%20of%20high%20gradients%20of%20magnetic%20connectivity%20within%20quasi-separatrix%20layers%20%28QSLs%3B%20D%26eacute%3Bmoulin%20et%20al.%201996%29%2C%20preferred%20sites%20for%20reconnection%20in%20the%20absence%20of%20null%20points.%20Our%20results%20thus%20extend%20the%20range%20of%20magnetic%20field%20configurations%20where%20reconnection-related%20phenomena%20can%20occur."},{"type":"text","text":"The%20high%20kernel%20speeds%20notably%20exceed%20those%20reported%20in%20the%20past%20%28e.g.%2C%20L%26ouml%3Brin%C4%8D%26iacute%3Bk%20et%20al%202019%29%2C%20often%20relying%20on%20304%26Aring%3B%20%28resp.%201600%26Aring%3B%29%20channel%20observations%20from%20SDO%2FAIA%20at%20a%20cadence%20of%2012%20%28resp.%2024%29%20seconds.%20As%20a%20part%20of%20our%20investigation%2C%20we%20explored%20the%20importance%20of%20cadence%20on%20the%20instrument%E2%80%99s%20ability%20to%20detect%20the%20rapid%20kernel%20slippage.%20Figure%203%20compares%20stackplots%20constructed%20using%20the%20SJI%201330%20%28top%29%20and%20AIA%20304%20%28bottom%29%20data%20along%20the%20same%20artificial%20cut%2C%20and%20processed%20using%20the%20Sobel%20operator%20for%20the%20edge%20detection.%20The%20magenta%20frames%20indicate%20traces%20of%20slipping%20kernels%20resolved%20in%20different%20datasets%20via%20an%20automatic%20feature%20detection%20algorithm%20available%20in%20the%20OpenCV%20library.%20Our%20statistics%20%28see%20Table%201%20in%20the%20manuscript%29%20show%20that%20the%20SJI%201330%20data%20present%20an%20order-of-magnitude%20improvement%20in%20terms%20of%20the%20number%20of%20kernels%20resolved%20compared%20to%20AIA%20304.%20In%20addition%2C%20the%20mean%20slipping%20velocities%20observed%20by%20IRIS%20are%20by%201%E2%80%942%20orders%20of%20magnitude%20higher%20than%20those%20visible%20in%20the%20AIA%20304%20and%201600%20stackplots%2C%20respectively.%20By%20degrading%20the%20original%20SJI%201330%20observations%20we%20found%20that%20cadence%20of%20around%204%20seconds%20is%20needed%20to%20resolve%20the%20rapid%20kernel%20slippage%20at%20speeds%20exceeding%201000%20km%2Fs."},{"type":"image","file":"","url":"nuggetvideos/2024/10/23/pod_polito_vanessa_2024-10-23T00%3A04%3A39.105Z/Fig3.png","hash":"28b2ae5870138f1fac33170fd6fad179","mimeType":"image/png","caption":"Figure%203%3A%20Top%20panel%20presents%20the%20same%20stackplot%20as%20in%20Figure%202%2C%20but%20processed%20using%20the%20Sobel%20operator.%20The%20stackplot%20in%20the%20bottom%20panel%20was%20produced%20via%20the%20artificial%20cut%20indicated%20in%20Figure%201%2C%20but%20using%20the%20AIA%20304%20data.%20The%20magenta%20frames%20in%20both%20panels%20indicate%20the%20kernel%20traces%20detected%20using%20the%20automatic%20feature%20detection%20method%20%28see%20Methods%20in%20L%26ouml%3Brin%C4%8D%26iacute%3Bk%20et%20al.%202024%29."},{"type":"text","text":"This%20result%20evidences%20that%20the%20high%20cadence%20of%20IRIS%20played%20a%20crucial%20role%20in%20this%20discovery%20and%20places%20important%20constraints%20on%20the%20time%20resolution%20of%20future%20instrumentation%20focused%20on%20dynamic%20phenomena%20such%20as%20flares.%20The%20automatic%20detection%20of%20kernel%20traces%20powered%20by%20computer%20vision%20offers%20a%20very%20robust%20tool%20for%20a%20more%20comprehensive%20comparative%20analysis%20of%20kernel%20traces%20in%20a%20larger%20selection%20flares%20observed%20at%20a%20high%20cadence%2C%20to%20be%20conducted%20in%20the%20near%20future."}],"references":["<a href=\"https://ui.adsabs.harvard.edu/abs/1996A%26A...308..643D/abstract\">Demoulin, P. et al., (1996)</a>","<a href=\"https://ui.adsabs.harvard.edu/abs/2004SoPh..222..279F/abstract\">Fletcher, L. et al., SoPh 222, 279 (2004)</a>","<a href=\"ttps://ui.adsabs.harvard.edu/abs/2004ApJ...604..900Q/abstract\">Qiu, J. et al., ApJ 604, 900 (2004)</a>","<a href=\"https://ui.adsabs.harvard.edu/abs/2006SoPh..238..347A/abstract\">Aulanier, G. et al., SoPh 238, 347 (2006)</a>","<a href=\"https://ui.adsabs.harvard.edu/abs/2013A%26A...555A..77J/abstract\">Janvier, M. et al., A&A 555, 77 (2013)</a>","<a href=\"https://ui.adsabs.harvard.edu/abs/2014ApJ...784..144D/abstract\">Dudik, J. et al., ApJ 784, 144 (2014)</a>","<a href=\"https://ui.adsabs.harvard.edu/abs/2016ApJ...823...41D/abstract\">Dudik, J. et al., ApJ 823, 41 (2016)</a>","<a href=\"https://ui.adsabs.harvard.edu/abs/2019ApJ...881...68L/abstract\">Lorincik, J. et al., ApJ 881, 68 (2019)</a>","<a href=\"https://ui.adsabs.harvard.edu/abs/2024NatAs.tmp..255L/abstract\">Lorincik, J. et al., NatAs (online) (2024)</a>",""],"pubDate":"2024-10-31T13:21:49.194Z"}