IRIS Nugget
Welcome to the IRIS Science Nuggets: highlights of recent IRIS scientific results for the solar physics community.
{"id":"pod_polito_vanessa_2024-03-05T19:00:56.574Z","submitter":"Seray Sahin","author":"Seray Sahin[1], Patrick Antolin[1], Clara Froment[2], Thomas A. Schad[3]","status":"published","creation-date":"2024-03-05T19:00:56.614Z","last-modified-date":"2024-03-09T10:23:17.603Z","credit":"[1] Department of Mathematics, Physics and Electrical Engineering, Northumbria University, Newcastle Upon Tyne, NE1 8ST, UK, [2] LPC2E, CNRS/University of Orleans/CNES, 3A avenue de la Recherche Scientifique, Orleans, France, [3] National Solar Observatory, 22 Ohia Ku Street, Pukalani, HI 96768, USA","title":"Spatial and Temporal Analysis of Quiescent Coronal Rain over an Active Region","contentBlocks":[{"type":"text","text":"The%20solar%20corona%20contains%20cool%20and%20dense%20plasma%20structures%2C%20such%20as%20prominences%20and%20coronal%20rain%2C%20in%20addition%20to%20being%20hot%2C%20tenuous%2C%20and%20diffuse.%20Coronal%20rain%20is%20magnetized%20plasma%20that%20cools%20and%20condenses%20along%20coronal%20loops%2C%20producing%20spectacular%20showers%20of%20plasma%20that%20can%20be%20observed%20with%20high-resolution%20instruments.%20Coronal%20rain%20has%20been%20a%20subject%20in%20solar%20physics%20since%20the%201970s%20%28Leroy%201972%29%3B%20however%2C%20it%20has%20only%20been%20significantly%20studied%20in%20the%20last%20decade%20because%20it%20was%20considered%20simply%20downflows%20from%20prominence%20structures.%20Coronal%20rain%20is%20intimately%20linked%20to%20one%20of%20the%20most%20enduring%20mysteries%20in%20astrophysics%3A%20the%20coronal%20heating%20problem.%20%0A%0AThe%20prevailing%20hypothesis%20regarding%20coronal%20rain%20formation%20suggests%20that%20it%20arises%20from%20thermal%20instability%20%28TI%29%20within%20coronal%20loops%20in%20a%20state%20of%20thermal%20non-equilibrium%20%28TNE%29%2C%20referred%20to%20as%20the%20TNE-TI%20scenario%20%28Antolin%202020%29.%20In%20this%20scenario%2C%20radiative%20cooling%20locally%20overcomes%20the%20coronal%20heating%20input%2C%20resulting%20in%20regions%20of%20cool%20and%20dense%20condensations%20called%20rain%20clumps%2C%20which%20subsequently%20fall%20as%20coronal%20rain%20toward%20the%20solar%20surface%20under%20the%20action%20of%20various%20forces%20%28Oliver%20et%20al.%202014%29.%20In%20the%20presence%20of%20steady%20and%20strongly%20stratified%20heating%20%28Klimchuk%20%26amp%3B%20Luna%202019%29%2C%20TNE-TI%20undergoes%20repetitive%20cycles%2C%20resulting%20in%20long-period%20EUV%20intensity%20pulsations%20and%20periodic%20rain%20occurrences%20%28Froment%20et%20al.%202020%29.%20Coronal%20rain%20is%20mainly%20observed%20in%20quiescent%20and%20flaring%20active%20regions%20%28AR%29%2C%20and%20correspondingly%20referred%20as%20quiescent%20%28QSr%29%20or%20flare-driven%20%28FDr%29%20coronal%20rain.%20The%20QSr%20is%20the%20most%20common%20type%20of%20coronal%20rain%20associated%20with%20AR%20coronal%20loops.%20FDr%20coronal%20rain%20is%20observed%20during%20the%20cooling%20phase%20%28known%20as%20gradual%20phase%29%20of%20a%20solar%20flare.%0A%0AIn%20this%20study%20%28Sahin%20et%20al.%202023%29%2C%20we%20performed%20the%20first%20large-scale%20statistical%20investigation%20of%20QSr%20rain%20over%20an%20AR%20off-limb%20with%20the%20Interface%20Region%20Imaging%20Spectrograph%20%28IRIS%29%20and%20Solar%20Dynamics%20Observatory%20%28SDO%29%20instruments%20%28see%20Figure%201%29%2C%20spanning%20chromospheric%20to%20transition%20region%20%28TR%29%20temperatures.%20We%20focused%20on%20the%20origin%2C%20dynamics%2C%20and%20morphology%20of%20quiescent%20coronal%20rain%2C%20contributing%20to%20our%20understanding%20of%20coronal%20heating%20mechanisms."},{"type":"image","file":"","url":"nuggetvideos/2024/03/05/pod_polito_vanessa_2024-03-05T19%3A00%3A56.574Z/Figure1.png","hash":"541f88fd0106bcacaddfcf492c582380","mimeType":"image/png","caption":"Figure%201.%20The%20studied%20AR%20at%20the%20east%20limb%20of%20the%20Sun%20on%202017%20June%202%2C%20observed%20by%20IRIS%2FSJI%202796%20%26Aring%3B%20%28left%29%2C%20SJI%201400%20%26Aring%3B%20%28second%20from%20left%29%20and%2C%20SDO%2FAIA%20304%20%26Aring%3B%20%28third%20from%20left%29.%20The%20separated%20panel%20on%20the%20right%20shows%20a%20wider%20FOV%20with%20SDO%2FAIA%20171%20%26Aring%3B%20over%20the%20same%20AR%2C%20with%20the%20white%20rectangle%20outlining%20the%20FOV%20shown%20in%20the%20left%20panels.%20All%20images%20were%20obtained%20summing%20over%20ten%20images%20in%20the%20interval%2007%3A28%3A00%20%E2%80%93%2007%3A34%3A28%20UT.%20An%20animation%20of%20this%20figure%20is%20available%20in%20Sahin%20et%20al.%202023."},{"type":"text","text":"We%20detected%20coronal%20rain%20during%20the%205.45-hour%20observational%20time%20using%20the%20Rolling%20Hough%20Transform%20%28RHT%29%20technique%20developed%20by%20Schad%20%282017%29.%20Figure%202%20presents%20the%20average%20spatial%20%28rain%20inclination%29%20and%20temporal%20%28dynamical%20change%29%20mean%20angle%20maps%20of%20all%20detected%20rain%20pixels%20derived%20from%20RHT.%20We%20found%20that%20coronal%20rain%20is%20pervasive%20around%20the%20AR%20with%20similar%20quantities%2C%20morphologies%2C%20and%20dynamics%20throughout%2C%20suggesting%20that%20coronal%20heating%20operates%20in%20a%20similar%20manner%20over%20a%20very%20wide%20area%20around%20the%20sunspot.%20Sahin%20and%20Antolin%20%282022%29%20observed%20widespread%20rain%20showers%20over%20the%20same%20AR%20and%20estimated%20the%20TNE%20volume%20to%20be%20at%20least%2050%25%20of%20the%20AR%20volume%2C%20suggesting%20the%20prevalence%20of%20TNE%20over%20the%20AR.%20The%20finding%20also%20reveals%20that%20most%20of%20the%20coronal%20rain%20exhibits%20a%20downward%20motion%20%2887.5%25%3B%20negative%20values%20in%20Figure%202%29%2C%20as%20expected%20due%20to%20the%20solar%20gravity.%20However%2C%20upward%20motions%20are%20also%20ubiquitous%20%2812.5%25%3B%20positive%20values%20in%20Figure%202%29."},{"type":"image","file":"","url":"nuggetvideos/2024/03/05/pod_polito_vanessa_2024-03-05T19%3A00%3A56.574Z/Figure2.png","hash":"23e7f64e4d0dff59ec5c2c1a0919e7ec","mimeType":"image/png","caption":"Figure%202.%20The%20average%20spatial%20%28top%29%20and%20temporal%20%28bottom%29%20mean%20angle%20maps%20over%20the%20entire%20time%20sequences%20as%20derived%20using%20the%20RHT%20technique.%20The%20spatial%20mean%20angle%20maps%20indicate%20the%20inclination%20of%20the%20rain%20with%20respect%20to%20the%20vertical%20direction%2C%20while%20temporal%20mean%20angle%20maps%20indicate%20the%20dynamical%20change%20along%20a%20trajectory.%20The%20dashed%20black%20curves%20indicate%20the%20solar%20limb."},{"type":"text","text":"Figure%203%20shows%20the%20histogram%20distribution%20of%20the%20downflow%20projected%20velocities%20%28a%29%2C%20widths%20%28b%29%2C%20lengths%20%28c%29%2C%20and%20their%20variation%20with%20height%20%28d%2C%20e%2C%20f%2C%20respectively%29.%20On%20the%20dynamical%20side%2C%20rain%20has%20a%20broad%20velocity%20distribution%20varying%20from%20a%20few%20km%20s%5Cbegin%7Bequation%7D%20%5E%7B-1%7D%20%5Cend%7Bequation%7D%20to%20%26gt%3B150%20km%20s%5Cbegin%7Bequation%7D%20%5E%7B-1%7D%20%5Cend%7Bequation%7D.%20Small%20downward%20accelerations%20were%20found%20at%20higher%20heights%2C%20specifically%20between%2030%20and%2040%20Mm.%20Nevertheless%2C%20coronal%20rain%20remains%20almost%20at%20constant%20velocities%20during%20most%20of%20the%20fall%2C%20exhibiting%20only%20a%20slight%20linear%20increase%20on%20average%20%28see%20panel%20d%29.%20This%20linear%20increase%20at%20lower%20heights%20may%20be%20a%20combination%20of%20effective%20gravity%20and%20pressure%20restructuring%20%28Oliver%20et%20al.%202014%3B%20Martinez-Gomez%20et%20al.%202020%29.%20The%20analysis%20of%20rain%20dynamics%20across%20the%20observed%20temperature%20range%20also%20indicates%20a%20striking%20similarity%2C%20suggesting%20a%20co-location%20on%20average%20between%20TR%20and%20chromospheric%20emissions.%0A%0AThe%20findings%20concerning%20the%20widths%20suggest%20that%20the%20factors%20defining%20coronal%20rain%20widths%20act%20promptly%20upon%20formation%20and%20remain%20relatively%20constant%20along%20the%20lengths%20of%20the%20loops%20during%20their%20fall%2C%20indicating%20the%20fundamental%20scale%20at%20which%20coronal%20heating%20or%20cooling%20occurs%20%28Antolin%20et%20al.%2C%202022%29.%20Overall%2C%20the%20average%20clumps%E2%80%99%20widths%20and%20lengths%20are%20comparable%20across%20the%20investigated%20temperature%20range."},{"type":"image","file":"","url":"nuggetvideos/2024/03/05/pod_polito_vanessa_2024-03-05T19%3A00%3A56.574Z/Figure3.png","hash":"391552d159a9d7e841a0476700a3c25b","mimeType":"image/png","caption":"Figure%203.%20Histograms%20of%20rain%20clump%20downflow%20projected%20velocities%20%28a%29%2C%20widths%20%28b%29%2C%20lengths%20%28c%29%2C%20and%20their%20variation%20with%20height%20%28d%2C%20e%2C%20f%29%2C%20respectively%2C%20in%20SJI%201400%20%26Aring%3B%2C%20%28red%29%2C%20SJI%202796%20%26Aring%3B%2C%20%28blue%29%2C%20and%20AIA%20304%20%26Aring%3B%20%28green%29%2C%20with%20corresponding%20median%20and%20standard%20deviation%20in%20the%20inner%20caption."},{"type":"text","text":"In%20Figure%204%20%28left%20panel%29%2C%20we%20show%20the%20contours%20of%20some%20of%20the%20detected%20EUV-pulsation%20regions%20in%20AIA%20171%20%26Aring%3B%20%28cyan%29%20and%20AIA%20193%20%26Aring%3B%20%28blue%29%20over%20an%20AIA%20171%20image%20of%20the%20AR%20with%20the%20overlaid%202796%20%26Aring%3B%20spatial%20mean%20angle%20map%20from%20coronal%20rain%20given%20in%20Figure%202.%20We%20found%20a%20widespread%20occurrence%20of%20long-period%20EUV-intensity%20pulsations%20associated%20with%20the%20observed%20rain%2C%20all%20located%20at%20the%20apex%20of%20the%20loops%20and%20with%20periods%20between%203-%20and%209-hr%20%28see%20right%20panel%20in%20Figure%204%20for%20one%20contour%20region%29%2C%20strengthening%20the%20result%20of%20Froment%20et%20al.%20%282020%29%20that%20the%20two%20phenomena%20are%20two%20sides%20of%20the%20same%20coin%2C%20linked%20through%20the%20TNE-TI%20scenario."},{"type":"image","file":"","url":"nuggetvideos/2024/03/05/pod_polito_vanessa_2024-03-05T19%3A00%3A56.574Z/Figure4.png","hash":"a2e8e415d37d8739f1f54fa55524dc10","mimeType":"image/png","caption":"Figure%204.%20Left%3A%20Location%20over%20the%20AR%20of%20the%20long-period%20EUV%20intensity%20pulsations%20in%20AIA%20171%20%26Aring%3B%20%28cyan%29%20and%20AIA%20193%20%26Aring%3B%20%28blue%29%20with%20normalized%20Fourier%20power%20above%2010%5Cbegin%7Bequation%7D%20%5Csigma%20%5Cend%7Bequation%7D.%20Each%20contour%20is%20labelled%20with%20the%20corresponding%20dominating%20frequency%3A%2075.97%5Cbegin%7Bequation%7D%20%5Cmu%20%5Cend%7Bequation%7DHz%2F3.65-hr%20%281%29%2C%2065.28%5Cbegin%7Bequation%7D%20%5Cmu%20%5Cend%7Bequation%7DHz%2F4.25-hr%20%282%29%2C%2038.40%5Cbegin%7Bequation%7D%20%5Cmu%20%5Cend%7Bequation%7DHz%2F7.23-hr%20%283%29%2C%2049.92%5Cbegin%7Bequation%7D%20%5Cmu%20%5Cend%7Bequation%7DHz%2F5.56-hr%20%284%29.%20We%20overlay%20the%20spatial%20mean%20angle%20map%20obtained%20with%20the%20RHT%20from%20the%20IRIS%202796%20%26Aring%3B%20images.%20Right%3A%20AIA%20171%20%26Aring%3B%20map%20with%20label-1%20regions%20%28cyan%29.%20The%20pink%20square%20is%20the%20subregion%20for%20the%20detailed%20analysis.%20Top-right%3A%20AIA%20171%20%26Aring%3B%20intensity%20evolution%20over%20the%20observational%20period%20summed%20over%20the%20subregion.%20The%20dashed%20vertical%20line%20shows%20the%20time%20of%20the%20right%20map%2C%20while%20the%20vertical%20blue%20dotted%20lines%20indicate%20the%20observation%20time%20window%20of%20the%20IRIS%20instrument%20%28i.e.%2C%205.45-hr%29.%20Bottom-left%3A%20the%20normalized%20power%20map%20of%20AIA%20171%20%26Aring%3B%20in%20logarithmic%20scale%20at%2075.97%5Cbegin%7Bequation%7D%20%5Cmu%20%5Cend%7Bequation%7DHz%20%283.65-hr%29.%20Bottom-right%3A%20Fourier%20power%20spectrum%20of%20the%20AIA%20171%20%26Aring%3B%20light%20curve."}],"references":["<a href=\"https://ui.adsabs.harvard.edu/abs/2020PPCF...62a4016A/abstract\">Antolin, P., Plasma Phys. Control. Fusion 62(1), 014016 (2020)</a>","<a href=\"https://ui.adsabs.harvard.edu/abs/2022ApJ...926L..29A/abstract\"> Antolin, P., Martinez-Sykora, J., and Sahin, S. ApJL 926(2), L29 (2022)</a>","<a href=\"https://ui.adsabs.harvard.edu/abs/2020A%26A...633A..11F/abstract\">Froment, C., Antolin, P., Henriques, V. M. J., Kohutova, P. and Rouppe van der Voort, L. H. M. A&A 633, A11 (2020)</a>","<a href=\"https://ui.adsabs.harvard.edu/abs/2019ApJ...884...68K/abstract\">Klimchuk, J.A. and Luna, M. ApJ 884(1), 68 (2019)</a>","<a href=\"https://ui.adsabs.harvard.edu/abs/1972SoPh...25..413L/abstract\">Leroy, J.-L., SoPhys 25(2), 413-417 (1972)</a>","<a href=\"https://ui.adsabs.harvard.edu/abs/2020A%26A...634A..36M/abstract\">Martinez-Gomez, D., Oliver, R., Khomenko, E., Collados, M. A&A 634, A36 (2020)</a>","<a href=\"https://ui.adsabs.harvard.edu/abs/2014ApJ...784...21O/abstract\">Oliver, R., Soler, R., Terradas, J., Zaqarashvili, T. V. and Khodachenko, M. L. ApJ 784, 21 (2014)</a>","<a href=\"https://ui.adsabs.harvard.edu/abs/2022ApJ...931L..27S/abstract\">Sahin, S. and Antolin, P. ApJL 931(2), L27 (2022)</a>","<a href=\"https://ui.adsabs.harvard.edu/abs/2023ApJ...950..171S/abstract\">Sahin, S., Antolin, P., Froment, C. and Schad, T. A. ApJ 950(2), 171 (2023)</a>","<a href=\"https://ui.adsabs.harvard.edu/abs/2017SoPh..292..132S/abstract\">Schad, T., SoPhys 292(9), 132 (2017)</a>"],"pubDate":"2024-03-11T20:19:11.41Z"}