IRIS Nugget
Welcome to the IRIS Science Nuggets: highlights of recent IRIS scientific results for the solar physics community.
{"id":"pod_polito_vanessa_2024-05-30T15:45:17.742Z","submitter":"Ramada Sukarmadji","author":"A. Ramada C. Sukarmadji [1], Patrick Antolin [1]","status":"published","creation-date":"2024-05-30T15:45:17.776Z","last-modified-date":"2024-06-11T19:27:20.118Z","credit":"[1] Northumbria University","title":"Transverse MHD Waves as Signatures of Braiding-induced Magnetic Reconnection in Coronal Loops","contentBlocks":[{"type":"text","text":"The%20dissipation%20of%20Magnetohydrodynamic%20%28MHD%29%20waves%20and%20nanoflare-sized%20heating%20%28%5Cbegin%7Bequation%7D10%5E%7B24%7D%5Cend%7Bequation%7D%20erg%3B%20Parker%201988%29%20from%20magnetic%20reconnection%20are%20the%20two%20leading%20theories%20for%20the%20coronal%20heating%20problem.%20It%20is%20unclear%20how%20much%20heating%20is%20contributed%20by%20MHD%20waves%20and%20reconnection%2C%20and%20a%20direct%20observational%20signature%20to%20coronal%20reconnection%20could%20not%20be%20established%20until%20the%20discovery%20of%20nanojets%20by%20Antolin%20et%20al.%20%282021%29.%20Nanojets%20are%20small-scale%20and%20short-lived%20bursts%20%28%26lt%3B%20%7E500%20km%20in%20width%2C%20%26lt%3B%20%7E1500%20km%20in%20length%2C%20and%20lifetimes%20of%20%26lt%3B%20%7E25%20s%20on%20average%29%2C%20which%20are%20signatures%20of%20component%20magnetic%20reconnection%20in%20a%20braided%20field.%20This%20discovery%20allows%20the%20clear%20identification%20of%20reconnection-driven%20nanoflares%20from%20similar%20intensity%20bursts%20produced%20by%20other%20mechanisms.%0A%0AIt%20has%20been%20long%20known%20that%20magnetic%20reconnection%20can%20produce%20all%20kinds%20of%20MHD%20waves%20%28e.g.%20Petschek%201964%3B%20Parker%201991%3B%20Kigure%20et%20al.%202010%29.%20However%2C%20there%20are%20no%20direct%20observations%20of%20small-angle%20reconnection%20events%20leading%20to%20the%20commonly%20observed%20kink%20waves%2C%20in%20which%20their%20origin%20remains%20highly%20debated.%20In%20our%20recent%20work%20%28Sukarmadji%20%26amp%3B%20Antolin%202024%29%2C%20we%20present%20the%20first%20observation%20of%20transverse%20oscillations%20driven%20by%20small-angle%20reconnection%20events%20in%20a%20coronal%20loop%2C%20where%20the%20reconnections%20are%20identified%20by%20the%20presence%20of%20nanojets.%20%0A%0AThe%20observation%20of%20interest%20is%20of%20AR%2012192%2C%20taken%20on%20the%2029th%20October%202014%2C%20by%20the%20Interface%20Region%20Imaging%20Spectrograph%20%28IRIS%29%20in%20the%20SJI%201330%20filtergram%20and%20the%20Atmospheric%20Imaging%20Assembly%20%28AIA%29%20on%20board%20the%20Solar%20Dynamics%20Observatory%20%28SDO%29.%20Our%20focus%20is%20on%20a%20hot%20loop%20presented%20in%20Figure%201.%20At%20its%20apex%2C%20we%20observe%20around%20ten%20nanojets%20characterised%20as%20small%20jet-like%20structures%20with%20fast%20speeds%20and%20short%20timescales.%20Measurements%20taken%20from%20the%20three%20of%20the%20clearest%20nanojets%20%28N1%2C%20N2%2C%20and%20N3%29%20shown%20in%20Figure%202%20provide%20mean%20POS%20lengths%20and%20widths%20of%201500%20km%20and%20341%20km%2C%20respectively%2C%20velocities%20of%20156%20km%20s%5Cbegin%7Bequation%7D%5E%7B%E2%88%921%7D%5Cend%7Bequation%7D%2C%20lifetimes%20of%2019%20s%2C%20and%20kinetic%20and%20thermal%20energy%20releases%20of%20%20%5Cbegin%7Bequation%7D7.8%20%5Ctimes%2010%5E%7B24%7D%5Cend%7Bequation%7D%20erg%20and%20%5Cbegin%7Bequation%7D1.4%20%5Ctimes%2010%5E%7B25%7D%5Cend%7Bequation%7D%20erg%20per%20nanojet%2C%20which%20aligns%20with%20the%20previous%20observations%20by%20Antolin%20et%20al.%20%282021%29%20and%20Sukarmadji%20et%20al.%20%282022%29."},{"type":"image","file":"","url":"nuggetvideos/2024/05/30/pod_polito_vanessa_2024-05-30T15%3A45%3A17.742Z/fig1.png","hash":"527cb694f4cb97cb7ebed6b5717ad12d","mimeType":"image/png","caption":"Figure%201.%20The%20first%20two%20rows%20show%20the%20snapshots%20of%20the%20loop%20at%20the%20time%20when%20the%20nanojets%20are%20most%20visible%20in%20SJI%201330%20and%20AIA%20131%2C%20171%2C%20193%2C%20211%2C%20and%20304.%20The%20bottom%20row%20shows%20snapshots%20for%20selected%20emission%20bins%20from%20log%28T%29%20%3D%205.8%2C%206.2%2C%20and%206.4%20from%20the%20DEM%20analysis.%20Three%20of%20the%20clearest%20nanojets%20%28left%20to%20right%2C%20N1%2C%20N2%2C%20and%20N3%29%20at%20the%20apex%20are%20marked%20with%20the%20white%20arrows."},{"type":"text","text":"The%20nanojets%20are%20followed%20by%20transverse%20motions%20of%20the%20strands%2C%20initiated%20by%20the%20upward%20motion%20from%20the%20nanojets%2C%20seen%20in%20the%20time%E2%80%93distance%20diagrams%20of%20Figure%202%20between%20t%20%3D%20150%20and%20300%20s.%20The%20signatures%20of%20multiple%20strands%20oscillating%20can%20also%20be%20seen%20from%20the%20presence%20of%20multiple%20waves%20in%20the%20time%E2%80%93distance%20diagrams%2C%20with%20an%20example%20of%20two%20waves%20marked%20with%20%281%29%20and%20%282%29%20in%20panel%20A%20of%20Figure%202.%20These%20oscillations%20have%20a%20measured%20period%20of%20%5Cbegin%7Bequation%7D97%20%5Cpm%204%5Cend%7Bequation%7D%20s%20and%20an%20amplitude%20of%20%5Cbegin%7Bequation%7D21%20%5Cpm%202%5Cend%7Bequation%7D%20km%20s%5Cbegin%7Bequation%7D%5E%7B%E2%88%921%7D%5Cend%7Bequation%7D%2C%20and%20the%20fundamental%20mode%20is%20likely%20excited%20due%20to%20its%20occurrence%20at%20the%20apex.%20Prior%20to%20the%20nanojets%2C%20the%20loop%20did%20not%20show%20any%20oscillations%2C%20suggesting%20that%20the%20nanojets%20are%20the%20most%20likely%20trigger%20for%20the%20waves."},{"type":"image","file":"","url":"nuggetvideos/2024/05/30/pod_polito_vanessa_2024-05-30T15%3A45%3A17.742Z/fig2.png","hash":"6eaf52fa984258043aa3bb7172b0e2e3","mimeType":"image/png","caption":"Figure%202.%20The%20two%20panels%20of%20the%20left%20column%20show%20the%20same%20snapshot%20of%20the%20apex%20of%20the%20loop%20with%20nanojets.%20In%20the%20top%20panel%2C%20the%20three%20most%20visible%20nanojets%20are%20marked%2C%20and%20in%20the%20bottom%20panel%2C%20slices%20along%20the%20trajectory%20of%20the%20nanojets%20A%2C%20B%2C%20and%20C%20are%20taken%20to%20produce%20the%20time%E2%80%93distance%20diagrams%20in%20the%20first%20three%20panels%20of%20the%20right%20column.%20Signatures%20of%20multiple%20strands%20oscillating%20can%20also%20be%20seen%20from%20the%20presence%20of%20multiple%20waves%20in%20time-distance%20diagram%20A%2C%20where%20two%20waves%20are%20marked%20with%20%281%29%20and%20%282%29.%20The%20nanojets%20in%20the%20time%E2%80%93distance%20diagrams%20are%20marked%20with%20N1%E2%80%93N6.%20The%20white%20vertical%20lines%20in%20the%20time%E2%80%93distance%20diagrams%20mark%20the%20time%20of%20the%20snapshot%20from%20the%20left%20column.%20The%20region%20contained%20by%20the%20white%20contour%20line%20in%20the%20bottom%20panel%20of%20the%20left%20row%20shows%20the%20region%20used%20to%20produce%20the%20light-curve%20plot%20shown%20in%20the%20bottom%20panel%20of%20the%20right%20column.%20The%20light%20curves%20are%20constructed%20by%20summing%20over%20the%20intensity%20values%20within%20the%20contour%20at%20a%20given%20time%20stamp%20and%20then%20normalized.%20In%20the%20bottom%20we%20show%20a%20schematic%20for%20our%20interpretation%20of%20how%20a%20nanojet%20forms%20from%20reconnection%20due%20to%20misalignments%20between%20%5Cbegin%7Bequation%7D%5Cvec%7BB%7D_1%5Cend%7Bequation%7D%20and%20%5Cbegin%7Bequation%7D%5Cvec%7BB%7D_2%5Cend%7Bequation%7D.%20The%20resulting%20configuration%20is%20likely%20to%20be%20affected%20by%20the%20tension%20from%20the%20reconnection%2C%20which%20overshoots%20the%20resting%20configuration%20and%20therefore%20produces%20oscillations%2C%20as%20seen%20at%20t%20%3D%20t%5Cbegin%7Bequation%7D_3%5Cend%7Bequation%7D."},{"type":"text","text":"Upon%20considering%20two%20cases%20for%20the%20possible%20modes%3B%20standing%20or%20propagating%20modes%2C%20we%20estimate%20that%20the%20energy%20flux%20from%20the%20waves%20is%20on%20the%20order%20of%20%5Cbegin%7Bequation%7D10%5E%7B6%7D%E2%80%9310%5E%7B8%7D%5Cend%7Bequation%7D%20erg%20cm%5Cbegin%7Bequation%7D%5E%7B%E2%88%922%7D%5Cend%7Bequation%7Ds%5Cbegin%7Bequation%7D%5E%7B%E2%88%921%7D%5Cend%7Bequation%7D%2C%20which%20is%20sufficient%20to%20balance%20the%20energy%20losses%20for%20active%20regions%20%28Withbroe%20%26amp%3B%20Noyes%201977%29.%20The%20thermal%20energy%20increase%20from%20the%20DEM%20values%20at%20the%20apex%20presented%20in%20Figure%203%20also%20shows%20an%20increase%20to%20a%20maximum%20value%20of%20%5Cbegin%7Bequation%7D4.0%20%5Ctimes%2010%5E%7B25%7D%5Cend%7Bequation%7D%20erg%20just%20after%20the%20nanojets%20have%20stopped%20forming.%20This%20value%20is%20on%20the%20same%20order%20of%20magnitude%20as%20the%20nanojet%27s%20average%20total%20energy%20release%20of%20%5Cbegin%7Bequation%7D2.2%20%5Ctimes%2010%5E%7B25%7D%5Cend%7Bequation%7D%20erg%2C%20meaning%20that%20only%20a%20few%20nanojets%E2%80%99%20worths%20of%20energy%20are%20required%20to%20sustain%20the%20heating%20seen%20at%20the%20loop%27s%20apex."},{"type":"image","file":"","url":"nuggetvideos/2024/05/30/pod_polito_vanessa_2024-05-30T15%3A45%3A17.742Z/fig3.png","hash":"eca36bdd9b3a11d142f43e5197664888","mimeType":"image/png","caption":"Figure%203.%20The%20top%20row%20shows%20snapshots%20of%20the%20loop%20apex%20in%20IRIS%20SJI%201330%2C%20AIA%20304%2C%20and%20AIA%20171.%20The%20white%20line%20in%20each%20panel%20is%20the%20slice%20taken%20for%20the%20respective%20time%E2%80%93distance%20diagrams%20shown%20in%20the%20next%20three%20rows%2C%20where%20t%20%3D%200%20s%20corresponds%20to%2013%3A35%3A11%20UT.%20The%20time%E2%80%93distance%20diagrams%20have%20the%20white%20circles%20marking%20the%20position%20of%20the%20oscillations%20that%20are%20selected%20based%20on%20an%20intensity%20threshold%20that%20separates%20the%20loop%20from%20its%20surroundings.%20The%20vertical%20white%20line%20in%20the%20time%E2%80%93distance%20diagram%20shows%20the%20time%20of%20the%20snapshots%20in%20the%20respective%20panels%20above.%20In%20the%20time%E2%80%93distance%20diagrams%2C%20the%20green%20vertical%20lines%20mark%20the%20period%20where%20we%20observe%20clear%20oscillations%20in%20IRIS.%20The%20plot%20in%20the%20bottom%20row%20shows%20the%20thermal%20energy%20release%20change%20from%20t%20%3D%20t%5Cbegin%7Bequation%7D_0%5Cend%7Bequation%7D%2C%20for%20the%20region%20of%20the%20loop%20that%20appears%20to%20be%20oscillating%2C%20estimated%20from%20the%20DEM%20for%20the%20region%20bounded%20by%20the%20white%20contour%20in%20the%20AIA%20images."},{"type":"text","text":"This%20discovery%20provides%20major%20support%20to%20existing%20theories%20that%20transverse%20MHD%20waves%20can%20be%20a%20signature%20of%20reconnection%20and%20the%20coronal%20reconnection%20scenario%20identified%20by%20nanojets.%20It%20is%20likely%20that%20a%20large%20proportion%20of%20heating%20is%20still%20undetected%20through%20AIA%2C%20as%20the%20oscillations%20and%20nanojets%20are%20only%20clear%20in%20IRIS%2C%20and%20they%20were%20also%20only%20clearly%20detected%20thanks%20to%20the%20presence%20of%20coronal%20rain%20in%20the%20strands.%20A%20major%20open%20question%20is%20how%20often%20the%20small-angle%20reconnection%20leads%20to%20kink%20waves%20and%20whether%20a%20constant%20generation%20of%20nanojets%20could%20support%20the%20decayless%20kink%20oscillations%20commonly%20observed%20%28Nakariakov%20et%20al.%202021%29.%20If%20this%20is%20indeed%20the%20case%2C%20then%20braided%20field%20lines%20should%20be%20expected%20in%20oscillating%20loops%2C%20as%20we%20require%20numerous%20misalignments%20to%20consistently%20produce%20nanojets%20that%20would%20sustain%20a%20decayless%20oscillation.%20However%2C%20the%20kink%20waves%20observed%20in%20this%20event%20damp%20very%20quickly%2C%20leading%20to%20a%20question%20of%20whether%20unresolved%20reconnection%20processes%20power%20decayless%20oscillations."}],"references":["<a href=\"https://ui.adsabs.harvard.edu/abs/2021NatAs...5...54A/abstract\">Antolin P., Pagano P., Testa P., Petralia A. and Reale F., NatAs 5, 54 (2021)</a>","<a href=\"https://ui.adsabs.harvard.edu/abs/2010PASJ...62..993K/abstract\">Kigure H., Takahashi K., Shibata K., Yokoyama T. and Nozawa S., PASJ 62, 993 (2010)</a>","<a href=\"https://ui.adsabs.harvard.edu/abs/2021SSRv..217...73N/abstract\">Nakariakov V. M., Anfinogentov S. A., Antolin P. et al., SSRv 217, 73 (2021)</a>","<a href=\"https://ui.adsabs.harvard.edu/abs/1988ApJ...330..474P/abstract\">Parker, E. N., ApJ 330, 474 (1988)</a>","<a href=\"https://ui.adsabs.harvard.edu/abs/1991ApJ...372..719P/abstract\">Parker E. N., ApJ 372, 719 (1991)</a>","<a href=\"https://ui.adsabs.harvard.edu/abs/1964NASSP..50..425P/abstract\"> Petschek H. E., The Physics of Solar Flares, Proc. of the AAS-NASA Symp. ed W. N. Hess (Washington, DC: NASA) 425 (1964)</a>","<a href=\" https://ui.adsabs.harvard.edu/abs/2022ApJ...934..190S/abstract\"> Sukarmadji A. R. C., Antolin P. and McLaughlin J. A, ApJ 934, 190 (2022)</a>","<a href=\" https://ui.adsabs.harvard.edu/abs/2024ApJ...961L..17S/abstract\"> Sukarmadji, A. R. C., and Antolin P., ApJL 961, L17 (2024)</a>","<a href=\" https://ui.adsabs.harvard.edu/abs/1977ARA%26A..15..363W/abstract\"> Withbroe G. L. and Noyes R. W., ARA&A 15 363 (1977)</a>",""],"pubDate":"2024-06-11T21:56:52.875Z"}