IRIS Nugget
Welcome to the IRIS Science Nuggets: highlights of recent IRIS scientific results for the solar physics community.
{"id":"pod_polito_vanessa_2022-01-21T19:08:55.089Z","submitter":"Vishal Upendran","author":"Vishal Upendran [1] and Durgesh Tripathi [1]","status":"published","creation-date":"2022-01-21T19:08:55.092Z","last-modified-date":"2022-02-09T21:11:43.161Z","credit":"[1] Inter-University Centre for Astronomy and Astrophysics, Pune, India","title":"On the formation of solar wind & switchbacks, and quiet Sun heating","contentBlocks":[{"type":"text","text":"The%20highly%20stratified%20and%20dynamic%20solar%20atmosphere%2C%20with%20temperatures%20ranging%20from%20%E2%89%885500%20K%20to%20more%20than%20a%20million%20degrees%20Kelvin%2C%20is%20tightly%20coupled%20by%20the%20dynamics%20of%20the%20magnetic%20field.%20Coronal%20Holes%20%28CH%29%20are%20morphological%20features%20seen%20as%20a%20deficit%20in%20intensity%20over%20the%20background%20Quiet%20Sun%20%28QS%29%20in%20the%20corona.%20However%2C%20at%20lower%20temperatures%2C%20i.e.%2C%20in%20the%20transition%20region%20%28TR%29%20%20and%20in%20the%20chromosphere%2C%20the%20stark%20differentiation%20between%20the%20two%20regions%20vanishes%21%20An%20example%20is%20shown%20in%20Fig.%201%2C%20with%20the%20coronal%20image%20from%20193%20%26Aring%3B%20passband%20of%20Atmospheric%20Imaging%20Assembly%20%28AIA%3B%20Boerner%20et%20al.%202012%29%20and%20the%20TR%20%28chromosphere%29%20intensity%20maps%20obtained%20in%20Si%20IV%20%28C%20II%2C%20Mg%20II%20k3%29%20from%20the%20Interface%20Region%20Imaging%20Spectrograph%20%28IRIS%3B%20De%20Pontieu%20et%20al.%202014%29.%20While%20the%20QS%20shows%20a%20larger%20radiative%20loss%20in%20the%20corona%2C%20the%20CHs%20are%20well-known%20sources%20of%20the%20solar%20wind%20%28Tu%20et%20al.%2C%202005%29.%20Hence%2C%20with%20the%20advent%20of%20high-quality%20observations%2C%20we%20demonstrate%20that%20these%20phenomena%20-%20i.e.%2C%20the%20solar%20wind%20formation%20and%20excess%20radiative%20losses%20in%20QS%20-%20may%20be%20unified%20under%20a%20single%20underlying%20scenario%20by%20studying%20the%20differences%20and%20similarities%20between%20CHs%20and%20QS."},{"type":"image","file":"","url":"nuggetvideos/2022/01/21/pod_polito_vanessa_2022-01-21T19%3A08%3A55.089Z/singleplot_FOV.png","hash":"f4f38a9db0c49fd6776c57229ebdd864","mimeType":"image/png","caption":"Fig.%201%3A%20CHs%20%28dark%29%20and%20QS%20%28bright%29%20in%20the%20corona%20%28AIA%20193%20%26Aring%3B%29%2C%20TR%20%28Si%20IV%29%20and%20the%20chromosphere%20%28C%20II%2C%20Mg%20II%20k3%29%20with%20the%20regions%20demarcated%20by%20contours%20obtained%20by%20employing%20the%20segmentation%20scheme%20of%20Upendran%20et.%20al%202020."},{"type":"text","text":"While%20prior%20studies%20report%20no%20significant%20differentiation%20between%20CHs%20and%20QS%20in%20the%20TR%20and%20chromosphere%20%28Stucki%20et%20al.%201999%29%2C%20differences%20are%20observed%20if%20the%20underlying%20photospheric%20magnetic%20flux%20density%20%28%7CB%7C%29%20is%20considered%20%28Tripathi%20et%20al.%202021%29.%20In%20these%20two%20studies%20%28Upendran%20%26amp%3B%20Tripathi%202021a%2C%202021b%29%2C%20we%20consider%205%20IRIS%20rasters%20and%20the%20corresponding%20%7CB%7C%20from%20Helioseismic%20and%20Magnetic%20Imager%20%28HMI%3B%20Scherrer%20et%20al.%202012%29%20and%20study%20the%20properties%20of%20Si%20IV%201393%20%26Aring%3B%2C%20C%20II%201334%20%26Aring%3B%2C%20and%20Mg%20II%20h%20%26amp%3B%20k%20lines%20in%20CHs%20and%20QS%20as%20a%20function%20of%20the%20%7CB%7C.%0A%0AWe%20find%20that%3A%0A1.%20Intensities%20increase%20with%20%7CB%7C%20for%20both%20regions.%20For%20similar%20%7CB%7C%2C%20QS%20shows%20excess%20intensity%20in%20both%20chromosphere%20and%20TR%20%28Fig.%202a%29%2C%20with%20larger%20excess%20in%20TR.%0A2.%20TR%20and%20chromosphere%20are%20redshifted%20on%20an%20average%2C%20with%20the%20average%20velocity%20increasing%20with%20%7CB%7C%20%28Fig.%202b%29.%0A3.%20For%20similar%20%7CB%7C%2C%20average%20velocity%20is%20consistent%20between%20regions%20in%20the%20chromosphere%2C%20while%20QS%20shows%20larger%20redshifts%20in%20TR%20%28Fig.%202b%29."},{"type":"image","file":"","url":"nuggetvideos/2022/01/21/pod_polito_vanessa_2022-01-21T19%3A08%3A55.089Z/Comb.png","hash":"6b34dbeb004e4fc7c06835b58ef0eb03","mimeType":"image/png","caption":"Fig.%202%3A%20QS-CH%20differences%20as%20a%20function%20of%20%7CB%7C%20in%20the%20TR%20and%20chromosphere.%20The%20intensity%20ratio%20is%20depicted%20in%20panel%20a%20and%20velocity%20differences%20in%20other%20panels.%20Panel%20b%20depicts%20the%20difference%20in%20average%20velocity%2C%20while%20panels%20c%20%26amp%3B%20d%20show%20for%20the%20blue-%20and%20red%20shifted%20pixels%20alone.%20The%20quantities%20are%20binned%20in%20%7CB%7C%20to%20improve%20statistics%2C%20and%20the%20error%20bars%20are%20standard%20error%20over%20the%20mean."},{"type":"text","text":"Next%2C%20we%20separately%20consider%20the%20blue-shifted%20and%20red-shifted%20pixels%20to%20study%20the%20systematic%20effects%20of%20%7CB%7C%20on%20the%20signed%20velocities.%20We%20find%20the%20blue%20and%20redshifts%20to%20increase%20with%20%7CB%7C%2C%20with%20the%20CHs%20showing%20excess%20blueshifts%20in%20both%20the%20chromosphere%20and%20the%20TR%20%28see%20Fig.%202c%29.%20However%2C%20the%20QS%20shows%20excess%20redshifts%20in%20TR%2C%20while%20CHs%20show%20excess%20redshifts%20in%20the%20chromosphere%2C%20presenting%20a%20dichotomy%20between%20the%20chromosphere%20and%20TR%20%28see%20Fig.%202d%29.%0A%0ATo%20understand%20further%2C%20we%20investigate%20the%20cross-correlation%20between%20TR%20and%20chromospheric%20velocities.%20We%20find%3A%0A1.%20TR%20and%20chromospheric%20up-%20and%20downflows%20are%20well%20correlated%20%28Fig.%203a%26amp%3Bb%29.%0A2.%20TR%20upflows%20are%20also%20well%20correlated%20with%20chromospheric%20downflows%20%28Fig.%203c%29%2C%20while%20no%20correlations%20are%20seen%20vice-versa%20%28Fig.%203d%29.%0A3.%20QS%20shows%20excess%20deceleration%20of%20downflows.%0A4.%20CHs%20show%20excess%20acceleration%20of%20upflows."},{"type":"image","file":"","url":"nuggetvideos/2022/01/21/pod_polito_vanessa_2022-01-21T19%3A08%3A55.089Z/singleplot_SiMgk3correlation.png","hash":"8604a572c80d88ca30aa106f1ca76ff9","mimeType":"image/png","caption":"Fig.%203%3A%20TR%20and%20chromospheric%20flow%20correlations%2C%20with%20the%20TR%20flows%20depicted%20in%20bins%20of%20chromospheric%20flows.%20Note%20that%20up-flows%20are%20blueshifts%2C%20and%20downflows%20are%20redshifts"},{"type":"text","text":"These%20observations%20may%20be%20explained%20by%20impulsive%20heating%20in%20a%20stratified%20atmosphere%20and%20different%20magnetic%20field%20topologies%20in%20CHs%20and%20QS.%20In%20the%20CHs%20%28Fig.%204a%29%2C%20the%20lesser%20%28similar%29%20number%20of%20long%20%28short%29%20loops%20give%20rise%20to%20a%20deficit%20in%20intensity%20%28similar%20gross%20intensity%29%20when%20compared%20to%20QS%20in%20the%20corona%20%28TR%20and%20chromosphere%29.%20The%20excess%20open%20flux%20undergoes%20interchange%20reconnection%20with%20adjoining%20closed%20loops%20of%20different%20heights%2C%20leading%20to%20bidirectional%20flows.%20The%20upflows%20are%20preferentially%20accelerated%20along%20the%20open%20field%20under%20the%20assumption%20of%20mass%20flux%20conserving%20flows%20%26amp%3B%20reduced%20coronal%20pressure%20in%20CHs%20and%20are%20seen%20as%20excess%20CH%20upflows%2C%20while%20the%20downflows%20radiatively%20cool%20to%20be%20visible%20in%20cooler%20lines.%20The%20correlated%20downflows%20may%20be%20explained%20if%20a%20fraction%20of%20the%20up-flowing%20plasma%20may%20cool%20down%20and%20fall%20back%2C%20or%20reconnection%20events%20much%20higher%20in%20the%20atmosphere%20drive%20such%20flows.%20An%20interesting%20consequence%20of%20interchange%20reconnection%20is%20the%20potential%20for%20these%20kinked%20field%20lines%20to%20propagate%20outwards%20as%20switchbacks%20%28Zank%20et%20al.%202020%29%20-%20in%20such%20a%20scenario%2C%20the%20flows%20we%20obtain%20serve%20as%20strong%20constraints%20on%20the%20possibility%20of%20low%20atmosphere%20switchback%20formation."},{"type":"image","file":"","url":"nuggetvideos/2022/01/21/pod_polito_vanessa_2022-01-21T19%3A08%3A55.089Z/Topology.png","hash":"4362d3b1d45da9d266238ff76fc50ef1","mimeType":"image/png","caption":"Fig.4%3A%20A%20schematic%20depicting%20the%20proposed%20picture%20of%20impulsive%20heating%20occurring%20across%20different%20magnetic%20field%20topologies.%20In%20the%20left%20panel%2C%20we%20show%20a%20CH%20topology%2C%20including%20open%20funnel-like%20structure%20%28black%29%2C%20closed%20loops%20of%20varying%20sizes%20%28yellow%29%2C%20and%20impulsive%20events%20%28red%20asterisks%29%20due%20to%20interchange%20reconnection%20between%20the%20open%20and%20closed%20field%20lines%2C%20giving%20rise%20to%20bidirectional%20flows%20%28blue%20and%20red%20arrows%29.%20The%20kinked%20field%20line%20propagating%20outward%20as%20a%20switchback%20is%20depicted%20as%20a%20dashed%20line%2C%20with%20the%20approximate%20propagation%20direction%20by%20black%20arrows.%20Right%20panel%3A%20QS%20topology%20shown%20with%20the%20same%20terminology%20as%20left%20panel."},{"type":"text","text":"Finally%2C%20the%20QS%20contains%20closed-loop%20structures%20predominantly%20%28see%20Fig.%204b%29%2C%20and%20closed-loop%20reconnection%20very%20much%20gives%20rise%20to%20the%20various%20correlated%20flows.%20However%2C%20due%20to%20confined%20plasma%20within%20loops%2C%20downflows%20are%20preferentially%20decelerated%20more%20in%20QS%20over%20CHs%2C%20while%20the%20upflows%20are%20not%20accelerated%20in%20this%20topology.%20Thus%2C%20a%20unified%20reconnection%20mechanism%20in%20different%20magnetic%20field%20topological%20settings%20elegantly%20gives%20rise%20to%20coronal%20heating%2C%20solar%20wind%20origin%2C%20and%20switchback%20formation."}],"references":["<a href=\"https://ui.adsabs.harvard.edu/abs/2021arXiv211111668U/abstract\">Vishal Upendran and Durgesh Tripathi ApJ (accepted) </a>","<a href=\"https://ui.adsabs.harvard.edu/abs/2021ApJ...922..112U/abstract\"> Vishal Upendran and Durgesh Tripathi 2021 ApJ 922 112 </a>","<a href=\"https://ui.adsabs.harvard.edu/abs/2020SpWea..1802478U/abstract\"> Upendran. V et al. (2020). Space Weather, 18, e2020SW002478 </a>","<a href=\"https://iopscience.iop.org/article/10.3847/1538-4357/abcc6b\">Durgesh Tripathi et al 2021 ApJ 908 28</a>","<a href=\"https://link.springer.com/article/10.1007%2Fs11207-014-0485-y\">De Pontieu et al. 2014, Solar Physics, 289, 2733 </a>","<a href=\"https://link.springer.com/article/10.1007%2Fs11207-011-9804-8\">Boerner, P. et al. 2012, SoPh, 275, 41</a>","<a href=\"https://link.springer.com/article/10.1007%2Fs11207-011-9834-2\">Scherrer, P. H et al. 2012, SoPh, 275, 207 </a>","<a href=\"https://link.springer.com/article/10.1023%2FA%3A1005145828283\">Stucki, K et al. Space Science Reviews 87, 315âÂÂ318 (1999). </a>","<a href=\"https://www.science.org/doi/10.1126/science.1109447\"> Tu, C.-Y et al. 2005, Science, 308, 519</a>","<a href=\"https://iopscience.iop.org/article/10.3847/1538-4357/abb828\">G. P. Zank et al 2020 ApJ 903 1</a>"],"pubDate":"2022-02-09T21:12:07.272Z"}