IRIS Nugget
Welcome to the IRIS Science Nuggets: highlights of recent IRIS scientific results for the solar physics community.
{"id":"pod_polito_vanessa_2022-03-22T16:10:52.903Z","submitter":"","author":"Hechao Chen[1], Hui Tian[1,2], Leping Li[2], Hardi Peter[3], Lakshmi Pradeep Chitta[3], Zhenyong Hou[1]","status":"published","creation-date":"2022-03-22T16:10:52.906Z","last-modified-date":"2022-04-07T17:23:25.293Z","credit":"[1] School of Earth and Space Sciences, Peking University, China. [2] CAS, National Astronomical Observatories, China. [3] Max Planck Institute for Solar System Research, Germany","title":"Coronal condensation as the source of quasi-steady supersonic downflows into sunspots","contentBlocks":[{"type":"text","text":"In%20the%201980s%2C%20downflows%20at%20supersonic%20speeds%20towards%20sunspots%20were%20discovered%20in%20the%20transition%20region%20%28TR%29%20spectra.%20With%20the%20launch%20of%20the%20Interface%20Region%20Imaging%20Spectrograph%20%28IRIS%29%2C%20a%20wealth%20of%20observational%20data%20of%20sunspots%20at%20high%20spatial%20and%20spectral%20resolutions%20have%20revealed%20that%20these%20TR%20supersonic%20downflows%20%28SDs%29%20commonly%20exist%20above%20the%20majority%20of%20sunspots%20%28Samanta%20et%20al.%202018%29.%20In%20IRIS%20spectra%2C%20they%20are%20often%20observed%20as%20strongly%20redshifted%20secondary%20emission%20peaks%20with%20a%20speed%20of%20%7E100%20km%2Fs%20and%20last%20for%20at%20least%20several%20hours%20%28e.g.%3B%20Tian%20et%20al.%202014%3B%20Straus%20et%20al.%202015%3B%20Chitta%20et%20al.%202016%29%20%28See%20Figure%201%29.%20However%2C%20how%20these%20long-lived%20supersonic%20downflows%20form%20and%20what%20mechanisms%20are%20responsible%20for%20the%20substantial%20and%20stable%20mass%20supply%20has%20remained%20unclear%20for%20the%20past%20four%20decades."},{"type":"image","file":"","url":"nuggetvideos/2022/03/22/pod_polito_vanessa_2022-03-22T16%3A10%3A52.903Z/iris0_ok.png","hash":"71f63b3da527206cf4af36f11863e9ae","mimeType":"image/png","caption":"Figure%201.%20IRIS%20observations%20of%20sunspot%20supersonic%20downflows%20%28SDs%29.%20%28a%29%20Image%20of%20an%20IRIS%20raster%20scan%20at%20Mg%20II%20k%202803.43%20%26Aring%3B.%20Coronal%20rain%20flows%20into%20the%20sunspot%20along%20the%20yellow%20arrow.%20%28b%29%20Spatial%20extent%20of%20SDs%20as%20shown%20the%20intensity%20images%20of%20the%20secondary%20component%20of%20Si%20IV%201400%20%26Aring%3B%20integrated%20in%20the%20velocity%20range%20of%2050%20km%2Fs%20to%20300%20km%2Fs%20.%20%28c%29%20Average%20spectrum%20in%20the%20small%20red%20box%20%283%E2%80%B2%E2%80%B2%20%26times%3B%203%E2%80%B2%E2%80%B2%20%29%20shown%20in%20panel%20b%20%28Raster%202%29.%20A%20six-component%20Gaussian%20fit%20to%20the%20spectrum%20is%20shown%20as%20the%20red%20%28primary%20component%29%20and%20blue%20lines%20%28secondary%20component%29."},{"type":"text","text":"With%20joint%20observations%20from%20IRIS%20and%20several%20other%20telescopes%20at%20multiple%20vantage%20points%2C%20Chen%20et%20al.%20%282022%29%20have%20recently%20investigated%20a%20series%20of%20TR%20SDs%20in%20NOAA%20AR%2012740%20%28see%20Figure%201%29%20and%20their%20associated%20coronal%20dynamic%20processes.%20They%20clearly%20tracked%20the%20formation%20of%20a%20quasi-steady%20SD%20event%20for%20the%20first%20time.%20Dual-perspective%20EUV%20imaging%20observations%20%28see%20Figures%202%20and%203%29%20reveal%20that%20these%20downflows%20originate%20from%20the%20cooling%20and%20condensation%20of%20hot%20coronal%20plasma%20at%20magnetic%20dips%20along%20a%20large-scale%20closed%20magnetic%20loop%20system%20spanning%20the%20sunspot%20region%20and%20a%20remote%20region.%20In%20the%20magnetic%20dip%20region%2C%20repeated%20coronal%20rain%20forms%20and%20continuously%20flows%20along%20these%20magnetic%20loops%20towards%20the%20sunspot%2C%20resulting%20in%20a%20TR%20SD%20event."},{"type":"image","file":"","url":"nuggetvideos/2022/03/22/pod_polito_vanessa_2022-03-22T16%3A10%3A52.903Z/2.png","hash":"4317af89bc409c511c4510b49aa96726","mimeType":"image/png","caption":"Figure%202.%20Quasi-steady%20supersonic%20downflows%20%28SDs%29%20resulting%20from%20a%20long-lived%20coronal%20rain%20event.%20%28a%29%20An%20IRIS%20SJI%201400%20%26Aring%3B%20image.%20SDs%20were%20best%20detected%20at%20the%20last%20slit%20position%20%28the%20black%20line%29.%20%28b1%29-%28b3%29%20Temporal%20evolution%20of%20the%20Si%20IV%201403%20%26Aring%3B%2C%20O%20IV%201401%20%26Aring%3B%2C%20and%20Mg%20II%202796%20%26Aring%3B%20line%20profiles%20averaged%20within%20the%20section%20marked%20by%20the%20green%20line%20shown%20in%20%28a%29.%20%28c%29%20The%20corresponding%20coronal%20rain%20event%20in%20an%20EUVI%20304%20%26Aring%3B%20image%20from%20a%20different%20perspective.%20The%20%28magnetic%29%20dip%20region%20is%20marked%20by%20the%20blue%20%26quot%3B%2B%26quot%3B%20sign.%20%28d%29%20Space-time%20diagram%20of%20EUVI%20304%20%26Aring%3B%20intensity%20for%20the%20trajectory%20%60%60S1%26quot%3B%20shown%20in%20panel%20%28c%29.%20The%20period%20of%20the%20IRIS%20four-step%20rasters%20is%20marked%20by%20the%20green%20solid%20line%20at%20the%20bottom.%20In%20%28a%29%20and%20%28c%29%2C%20the%20cyan%20plus%20signs%20mark%20the%20same%20heliocentric%20position%20after%20considering%20the%20solar%20rotation%2C%20and%20the%20yellow%20dashed%20line%20indicates%20the%20same%20altitude."},{"type":"text","text":"Based%20on%20imaging%20observations%20and%20magnetic%20field%20extrapolations%2C%20the%20authors%20proposed%20a%20reconnection-facilitated%20coronal%20condensation%20scenario%20%28see%20Figure%203b%20and%20also%20Li%20et%20al.%202018%29.%20In%20this%20scenario%2C%20the%20magnetic%20dips%20form%20slowly%20via%20reconnection%20of%20opposite-polarity%20coronal%20loops.%20With%20the%20presence%20of%20this%20dip%20region%2C%20the%20hot%20coronal%20plasma%20soon%20cools%20and%20condenses%20via%20thermal%20instability.%20In%20this%20process%2C%20condensed%20materials%20soon%20accumulate%20as%20a%20transient%20prominence%20in%20the%20dip%20region%20and%20thus%20form%20a%20mass%20reservoir%20available%20to%20feed%20a%20long-lasting%20rain%20flow.%20As%20the%20rain%20persistently%20drains%20into%20the%20sunspot%20along%20different%20trajectories%20in%20funnel-like%20magnetic%20structures%20%28sunspot%20plumes%29%2C%20the%20funnel%20effect%20of%20this%20magnetic%20geometry%20further%20reshapes%20the%20clumpy%20rain%20at%20the%20coronal%20height%20into%20a%20more%20elongated%20and%20stream-like%20one%20when%20reaching%20the%20lower%20atmosphere.%20This%20thus%20leads%20to%20the%20quasi-steady%20SDs."},{"type":"image","file":"","url":"nuggetvideos/2022/03/22/pod_polito_vanessa_2022-03-22T16%3A10%3A52.903Z/new2.png","hash":"2761b6d4ae68b9c5f9bdc086a23bc63e","mimeType":"image/png","caption":"Figure%203.%20Global%20view%20of%20coronal%20rain%2Fprominence%20activity%20and%20supersonic%20downflows%20%28SDs%29%20near%20the%20sunspot%20observed%20by%20STEREO-A%2FEUVI.%20%28a%29%20rotated%20171%20%26Aring%3B%20and%20304%20%26Aring%3B%20images.%20%28b%29%20a%20possible%20scenario%20for%20the%20formation%20of%20reconnection-facilitated%20coronal%20condensation%20and%20its%20induced%20quasi-steady%20SDs.%20%28c%29%20Magnetic%20dips%20reconstructed%20by%20the%20PFSS%20model."},{"type":"text","text":"The%20drainage%20of%20coronal%20rain%20and%20its%20resultant%20SDs%20last%20for%20more%20than%202%20hours%20%28Figure%202%20b%20and%20c%29%2C%20suggesting%20a%20substantial%20mass%20supply%20by%20the%20coronal%20condensation.%20In%20the%20dip%20region%2C%20the%20total%20mass%20of%20condensation%20%281.3%20%5Cbegin%7Bequation%7D%20%5Ctimes%2010%5E%7B14%7D%20%5Cend%7Bequation%7D%20g%29%20and%20condensation%20rate%20%20%281.5%20%5Cbegin%7Bequation%7D%20%5Ctimes%2010%5E%7B10%7D%20%20%5Cend%7Bequation%7D%20g%20%20%5Cbegin%7Bequation%7D%20s%5E%7B-1%7D%20%5Cend%7Bequation%7D%29%20were%20found%20to%20be%20large%20enough%20to%20sustain%20this%20long-lived%20SD%20event%2C%20which%20has%20a%20mass%20transport%20rate%20of%207.1-12.2%20%5Cbegin%7Bequation%7D%2010%5E9%20%5Cend%7Bequation%7D%20g%20%5Cbegin%7Bequation%7D%20s%5E%7B-1%7D%20%5Cend%7Bequation%7D.%20As%20downflows%20fall%20into%20the%20sunspot%2C%20they%20eventually%20impart%20their%20energy%20into%20the%20lower%20atmosphere%20of%20sunspots%20and%20result%20in%20a%20long-lived%20localized%20brightening%20in%20the%20umbra.%20This%20SD-induced%20chromospheric%20brightening%20was%20clearly%20imaged%20by%20a%20ground-based%20solar%20telescope%2C%20the%20New%20Vacuum%20Solar%20Telescope%20%28NVST%29%2C%20located%20in%20the%20Fuxian%20Solar%20Observatory%20of%20the%20Yunnan%20Astronomical%20Observatories%20of%20the%20Chinese%20Academy%20of%20Sciences.%20This%20indicates%20that%20SDs%20play%20an%20important%20role%20in%20the%20chromosphere-corona%20mass%20cycle%20of%20the%20sunspot%20atmosphere.%0A%0A%0AFor%20the%20full%20paper%2C%20please%20check%20out%20Chen%20et%20al.%20%282022%29."}],"references":["<a href=\"https://ui.adsabs.harvard.edu/abs/2018ApJ...859..158S/abstract\">Samanta, T., Tian, H., and Prasad Choudhary, D., ApJ 859, 158 (2018)</a>","<a href=\"https://ui.adsabs.harvard.edu/abs/2014ApJ...786..137T/abstract\">Tian, H., DeLuca, E., Reeves, K. K., et al., ApJ 786, 137 (2014)</a>","<a href=\"https://ui.adsabs.harvard.edu/abs/2015A%26A...582A.116S/abstract\">Straus, T., Fleck, B., and Andretta, V., A&A 582, A116 (2015)</a>","<a href=\"https://ui.adsabs.harvard.edu/abs/2016A%26A...587A..20C/abstract\">Chitta, L. P., Peter, H., and Young, P. R., A&A 587, A20 (2016)</a>","<a href=\"https://ui.adsabs.harvard.edu/abs/2022A%26A...659A.107C/abstract\">Chen, H., Tian, H., Li, L., et al., A&A 659, A107 (2022)</a>","<a href=\"https://ui.adsabs.harvard.edu/abs/2018ApJ...864L...4L/abstract\">Li, L., Zhang, J., Peter, H., et al., ApJL 864, L4 (2018)</a>","","","",""],"pubDate":"2022-04-11T20:54:55.238Z"}