IRIS Nugget
Welcome to the IRIS Science Nuggets: highlights of recent IRIS scientific results for the solar physics community.
{"id":"pod_polito_vanessa_2023-01-03T21:19:17.867Z","submitter":"A. Sainz Dalda (asainz.solarphysics@gmail.com)","author":"A. Sainz Dalda [1,2] and B. De Pontieu [1,3,4]","status":"published","creation-date":"2023-01-03T21:19:17.895Z","last-modified-date":"2023-01-13T19:32:16.073Z","credit":"[1] Lockheed Martin Solar & Astrophysics Laboratory, 3251 Hanover Street, Palo Alto, CA 94304, USA. [2] Bay Area Environmental Research Institute, NASA Research Park, Moffett Field, CA 94035, USA. [3] Rosseland Center for Solar Physics, University of Oslo, P.O. Box 1029 Blindern, NO-0315 Oslo, Norway. [4] Institute of Theoretical Astrophysics, University of Oslo, P.O. Box 1029 Blindern, NO-0315 Oslo, Norway","title":"Chromospheric Thermodynamic Conditions From Inversions of Complex Mg II h&k Profiles Observed in Flares","contentBlocks":[{"type":"text","text":"We%20have%20investigated%20the%20physical%20conditions%20in%20the%20chromosphere%20during%20the%20maximum%20of%20the%20X-class%20flare%20SOL2014-03-29%2017%3A48UT%20through%20the%20simultaneous%20inversion%20of%20the%20lines%20C%20II%201334%26amp%3B1335%20%26Aring%3B%2C%20the%20Mg%20II%20h%26amp%3Bk%20lines%2C%20and%20the%20Mg%20II%20UV%20triplet%20lines%20observed%20by%20IRIS%20%28De%20Pontieu%20et%20al.%2C%202014%29.%20The%20interpretation%20of%20these%20profiles%20has%20remained%20elusive%2C%20and%2C%20therefore%2C%20the%20physics%20associated%20with%20them%20as%20well.%20The%20main%20characteristic%20of%20these%20profiles%20is%20their%20pointy%20shape.%20By%20using%20the%20inversion%20with%20the%20state-of-the-art%20STiC%20code%20%28de%20la%20Cruz%20et%20al.%202019%29%20on%20the%20representative%20profiles%20%28calculated%20using%20the%20k-means%20technique%29%2C%20we%20have%20obtained%20the%20thermodynamics%20and%20we%20are%20able%20to%20give%20a%20feasible%20explanation%20of%20the%20physical%20conditions%20in%20the%20flare%20ribbons%20%28Sainz%20Dalda%20%26amp%3B%20De%20Pontieu%2C%202022%29."},{"type":"image","file":"","url":"nuggetvideos/2023/01/03/pod_polito_vanessa_2023-01-03T21%3A19%3A17.867Z/figure_1_nugget.png","hash":"d910c3ac3cb5a3eccb741f25937aa868","mimeType":"image/png","caption":"Figure%201.%20Thermodynamics%20of%20the%20X-class%20flare%20SOL2014-03-29%2017%3A48UT%20from%20the%20high%20chromosphere%20%28first%20row%29%20to%20the%20low%20chromosphere%20%28last%20row%29.%20The%20temperature%20%28%5Cbegin%7Bequation%7DT%5Cend%7Bequation%7D%2C%20in%20kK%29%2C%20line-of-sight%20velocity%20%28%5Cbegin%7Bequation%7Dv_%7Blos%7D%5Cend%7Bequation%7D%2C%20in%20km%2Fs%29%2C%20velocity%20of%20turbulent%20motions%20%28%5Cbegin%7Bequation%7Dv_%7Bturb%7D%5Cend%7Bequation%7D%2C%20in%20km%2Fs%29%2C%20and%20electron%20density%20%28log%20%5Cbegin%7Bequation%7Dn_%7Be%7D%5Cend%7Bequation%7D%29%20in%20cm-3%29%20are%20shown%20by%20columns%20%28left%20to%20right%20respectively%29%20at%20different%20optical%20depths%20averaged%20in%20an%20interval%20of%20%CE%94%CF%84%20%3D%20%2B%2F-0.2%20%28in%20rows%29."},{"type":"text","text":"Figure%201%20shows%20the%20thermodynamics%20during%20the%20maximum%20of%20the%20flare%20along%20the%20optical%20depth%2C%20%20log10%28%CF%84500%29.%20That%20is%2C%20the%20reference%20of%20the%20optical%20depth%20unity%20corresponds%20to%20the%20continuum%20at%20500%20nm.%20For%20the%20sake%20of%20simplicity%20in%20the%20notation%2C%20we%20use%20log%28%CF%84%29.%20As%20a%20rough%20reference%2C%20%0Awe%20consider%20the%20high%20chromosphere%20in%20the%20optical%20depth%20range%20%E2%88%926.5%20%26lt%3B%20log%28%CF%84%29%26lt%3B%20%E2%88%925%2C%20the%20mid%20chromosphere%20in%20%E2%88%925%20%26lt%3B%20log%28%CF%84%29%26lt%3B%20%E2%88%924%2C%20the%20low%20chromosphere%20in%20%E2%88%924%20%26lt%3B%20log%28%CF%84%29%26lt%3B%20%E2%88%922%2C%20and%20the%20high%20photosphere%20in%20%E2%88%922%20%26lt%3B%20log%28%CF%84%29%26lt%3B%20%E2%88%921.%20Although%20Figure%201%20shows%20a%20moment%20in%20the%20flare%20evolution%2C%20the%20different%20parts%20of%20the%20ribbon%20%28leading%20and%20trailing%20edges%29%20may%20be%20at%20different%20thermodynamic%20stages%20as%20the%20energy%20is%20propagating%20through%20the%20ribbon.%20Thus%2C%20in%20the%20high%20chromosphere%20%28first%20row%29%2C%20the%20temperature%20in%20the%20trailing%20edge%20of%20the%20lower%20ribbon%20%E2%80%94%20located%20at%20%5BX%2CY%5D%20%3D%20%5B517%20%E2%88%92%20526%2C%20263%5D%20%E2%80%94%20has%20a%20higher%20temperature%20%20than%20in%20the%20rest%20of%20the%20ribbon.%20That%20means%2C%20the%20trailing%20edge%20has%20been%20energized%20longer%20than%20the%20leading%20edge.%20In%20addition%2C%20in%20the%20trailing%20edge%20the%20temperature%20in%20the%20high%20chromosphere%20is%20higher%20than%20in%20the%20mid%20chromosphere.%20However%2C%20the%20inner%20part%20of%20the%20ribbon%20and%20the%20leading%20ribbon%2C%20%20the%20temperature%20in%20the%20high%20chromosphere%20%28first%20row%29%20is%20lower%20than%20in%20the%20mid%20chromosphere%20%28second%20row%20of%20Figure%201%29.%20These%20observations%20support%20a%20scenario%20in%20which%20energy%20is%20deposited%20in%20the%20middle%20chromosphere%2C%20with%20an%20associated%20local%20temperature%20increase.%20This%20energy%20deposition%20affects%20the%20high%20chromosphere%20at%20later%20times%20in%20the%20inner%20ribbon%20and%20the%20leading%20ribbon%2C%20as%20the%20flare%20evolves%2C%20but%20it%20has%20already%20affected%20to%20the%20trailing%20edge.%20Allred%20et%20al.%20%282015%29%20obtained%20a%20similar%20behavior%20in%20numerical%20models%20of%20flares%20energy%20deposition%20in%20the%20chromosphere.%0A%0AThe%20%5Cbegin%7Bequation%7Dv_%7Blos%7D%5Cend%7Bequation%7D%20in%20the%20ribbon%20shows%20a%20divergent%20behavior%20in%20the%20high-%20and%20mid-chromosphere%20%28first%20and%20second%20row%20respectively%20in%20the%20second%20column%20of%20Figure%201%29.%20Thus%2C%20we%20observe%20predominantly%20an%20upflow%20in%20the%20high%20chromosphere%20%28log%28%CF%84%29%3D%20%E2%88%925.8%29%2C%20while%20in%20the%20middle%20chromosphere%20and%20lower%20regions%20in%20the%20atmosphere%20%28%E2%88%924.2%20%26lt%3B%20log%28%CF%84%29%29%20we%20observe%20a%20downflow.%20This%20divergent%20flow%20is%20compatible%20with%20a%20scenario%20where%20an%20electron%20beam%20propagating%20downwards%20from%20the%20flare%20reconnection%20site%20in%20the%20corona%20impacts%20the%20dense%20chromosphere%20%28thick%20target%20model%29.%20Such%20divergent%20flows%20have%20also%20been%20obtained%20in%20radiation%20hydrodynamic%20experiments%20by%20Kerr%20et%20al.%202016%20and%20Kowalski%20et%20al.%202017.%20This%20divergent%20region%20is%20observed%20also%20in%20the%20leading%20edge%20in%20the%20low-chromosphere%20and%20high-chromosphere%2C%20making%20this%20scenario%20compatible%20with%20the%20results%20obtained%20by%20Graham%20et%20al.%202020%20and%20the%20one%20previously%20suggested%20by%20Libbrecht%20et%20al.%202019.%20Again%2C%20different%20parts%20of%20the%20ribbon%20are%20simultaneously%20experiencing%20different%20physical%20conditions."},{"type":"image","file":"","url":"nuggetvideos/2023/01/03/pod_polito_vanessa_2023-01-03T21%3A19%3A17.867Z/figure_2_nugget.png","hash":"9bf89573e12721e71134b7e468ea498d","mimeType":"image/png","caption":"Figure%202.%20Example%20of%20an%20extremely%20pointy%20profile.%20From%20top%20to%20bottom%2C%20from%20left%20to%20right%3A%20C%20II%201334%20%26amp%3B%201335%20%28panel%20A%29%2C%20Mg%20II%20UV1%20%28B%29%2C%20Mg%20II%20h%26amp%3Bk%20%28C%20and%20left%20and%20right%20sub-panels%20in%20panel%20C%29%2C%20and%20Mg%20II%20UV2%26amp%3B3%20%28C%20and%20center%20sub-panel%20in%20panel%20C%29%20lines.%20The%20observed%20profile%20is%20display%20in%20dotted%2C%20black%20line.%20The%20dashed%2C%20blue%20line%20corresponds%20to%20the%20inversion%20only%20taking%20into%20account%20the%20Mg%20II%20h%26amp%3Bk%20lines.%20The%20fuchsia%20line%20corresponds%20to%20the%20inversion%20considering%20simultaneously%20the%20C%20II%201334%20%26amp%3B%201335%20.%20lines%2C%20the%20Mg%20II%20UV1%20line%2C%20and%20the%20Mg%20II%20h%26amp%3Bk%20lines%20-%20including%20the%20Mg%20II%20UV2%26amp%3B3%20lines.%20The%20last%20row%20shows%20the%20model%20recovered%20from%20the%20inversion%3A%20temperature%20%28%5Cbegin%7Bequation%7DT%5Cend%7Bequation%7D%2C%20in%20orange%29%2C%20logarithm%20of%20the%20electron%20density%20%28%5Cbegin%7Bequation%7Dn_%7Be%7D%5Cend%7Bequation%7D%2C%20in%20blue%29%2C%20velocity%20of%20turbulent%20motions%20or%20micro-turbulence%20%28%5Cbegin%7Bequation%7Dv_%7Bturb%7D%5Cend%7Bequation%7D%2C%20in%20green%29%2C%20and%20line-of-sight%20velocity%20%28%5Cbegin%7Bequation%7Dv_%7Blos%7D%5Cend%7Bequation%7D%2C%20in%20violet%29.%20The%20dashed%20lines%20correspond%20to%20the%20model%20recovered%20from%20the%20inversion%20considering%20only%20the%20Mg%20II%20h%26amp%3Bk%20lines%2C%20while%20the%20solid%20lines%20correspond%20to%20the%20inversion%20considering%20all%20the%20spectral%20lines%20mentioned%20above.%20The%20red%20shade%20area%20in%20the%20model%20atmosphere%20panels%20%28D%20and%20E%29%20indicates%20the%20optical%20depth%20range%20that%20we%20should%20not%20consider%20as%20reliable."},{"type":"text","text":"These%20thermodynamic%20values%20have%20been%20obtained%20by%20the%20simultaneous%20inversion%20of%20the%20spectral%20lines%20mentioned%20above%2C%20that%20gives%20us%20an%20unprecedented%20coverage%20from%20the%20top%20of%20the%20chromosphere%20to%20the%20top%20of%20the%20photosphere.%20The%20Mg%20II%20h%26amp%3Bk%20spectral%20lines%20in%20the%20ribbon%20during%20the%20maximum%20of%20the%20flare%20are%20either%20extremely%20pointy%20profiles%20or%20combined%20pointy%20profiles.%20Figure%202%20shows%20an%20example%20of%20an%20extremely%20pointy%20profile%20%28in%20dotted%20line%29%2C%20the%20inverted%20profile%20%28best%20fit%20to%20the%20observed%20one%2C%20in%20fuchsia%29%2C%20and%20the%20thermodynamic%20parameters%20%28in%20the%20last%20row%29.%20These%20profiles%20are%20associated%20with%20strong%20gradients%20in%20the%20mid-%20and%20high-chromosphere%2C%20showing%20divergent%20flows%20in%20some%20instances.%20Figure%203%20shows%20an%20example%20of%20a%20combined%20pointy%20profile.%20In%20this%20case%2C%20we%20can%20observe%20the%20behavior%20mentioned%20above%3A%20a%20high%20temperature%20at%20log%28%CF%84%20%29%3D%20%E2%88%925.8%2C%20%20followed%20by%20a%20lower%20temperature%20in%20the%20high-chromosphere%20%28%28log%28%CF%84%20%29%3D%20%E2%88%926.4%29%2C%20i.e.%20the%20high-chromosphere%20has%20not%20been%20yet%20energized%20from%20the%20mid-chromosphere.%20The%20%5Cbegin%7Bequation%7Dv_%7Blos%7D%5Cend%7Bequation%7D%20shows%20a%20divergent%20flow%20in%20the%20low%20chromosphere%2C%20at%20log%28%CF%84%29%3D%20%E2%88%923.8."},{"type":"image","file":"","url":"nuggetvideos/2023/01/03/pod_polito_vanessa_2023-01-0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href=\"https://ui.adsabs.harvard.edu/abs/2015ApJ...809..104A\"> Allred, Kowalski, & Carlsson, The Astrophysical Journal, 809, 104 (2015)</a>","<a href=\"https://ui.adsabs.harvard.edu/abs/2019A&A...623A..74D\"> de la Cruz Rodríguez et al., Astronomy and Astrophysics, 623, A74 (2019)</a>","<a href=\"https://ui.adsabs.harvard.edu/abs/2014SoPh..289.2733D\"> De Pontieu et al., Solar Physics, 289, 2733 (2014)</a>","<a href=\"https://ui.adsabs.harvard.edu/abs/2020ApJ...895....6G\"> Graham et al., The Astrophysical Journal, 895, 6 (2020)</a>","<a href=\"https://ui.adsabs.harvard.edu/abs/2016ApJ...827..101K\"> Kerr et al., The Astrophysical Journal, 827, 101 (2016)</a>","<a href=\"https://ui.adsabs.harvard.edu/abs/2017ApJ...836...12K\"> Kowalski et al., The Astrophysical Journal, 836, 12 (2017)</a>","<a href=\"https://ui.adsabs.harvard.edu/abs/2019A&A...621A..35L\"> Libbrecht et al., Astronomy and Astrophysics, 621, A35 (2019)</a>","<a href=\"https://ui.adsabs.harvard.edu/abs/2022arXiv221105459S\"> Sainz Dalda & De Pontieu, arXiv e-prints, arXiv:2211.05459 (2022)</a>","",""],"pubDate":"2023-01-13T19:32:51.666Z"}