IRIS Nugget
Welcome to the IRIS Science Nuggets: highlights of recent IRIS scientific results for the solar physics community.
{"id":"pod_polito_vanessa_2022-02-24T21:30:07.698Z","submitter":"Ryan French (ryan.french.14@ucl.ac.uk)","author":"Ryan J. French [1], Sarah A. Matthews [1], I. Jonathan Rae [2], Andrew W. Smith [1]","status":"published","creation-date":"2022-02-24T21:30:07.729Z","last-modified-date":"2022-03-10T22:56:44.658Z","credit":"[1] UCL Mullard Space Science Laboratory. [2] Northumbria University.","title":"Probing Current Sheet Instabilities from Flare Ribbon Dynamics","contentBlocks":[{"type":"text","text":"Current%20sheet%20instabilities%2C%20such%20as%20the%20tearing%20mode%20instability%20%28Biskamp%201986%29%2C%20are%20needed%20to%20account%20for%20the%20observed%20rate%20of%20energy%20release%20in%20solar%20flares.%20Insights%20into%20current%20sheet%20dynamics%20can%20be%20revealed%20by%20the%20behavior%20of%20flare%20ribbon%20substructure%2C%20as%20magnetic%20reconnection%20accelerates%20particles%20down%20newly%20reconnected%20field%20lines%20into%20the%20chromosphere%20to%20mark%20the%20flare%20footpoints.%20In%20this%20study%2C%20we%20use%20high-cadence%20IRIS%20Slit%20Jaw%20Imager%20%28SJI%29%20observations%20to%20probe%20for%20growth%20and%20evolution%20of%20key%20spatial%20scales%20along%20flare%20ribbons%E2%80%94resulting%20from%20dynamics%20across%20the%20current%20sheet%20of%20a%20B-class%20flare%20on%202016%20December%206.%20Combining%20analyses%20of%20spatial%20scale%20growth%20with%20Si%20IV%20nonthermal%20velocities%2C%20we%20piece%20together%20a%20timeline%20of%20flare%20onset%20for%20this%20confined%20event%2C%20and%20provide%20evidence%20of%20the%20tearing%20mode%20instability%20triggering%20a%20cascade%20and%20inverse%20cascade%20toward%20a%20power%20spectrum%20consistent%20with%20plasma%20turbulence."},{"type":"image","file":"","url":"nuggetvideos/2022/02/24/pod_polito_vanessa_2022-02-24T21%3A30%3A07.698Z/IRIS_nugget_fig1.jpg","hash":"58cb6a9682c4b4839d1797c21de10834","mimeType":"image/jpeg","caption":"Figure%201%20%E2%80%93%20Evolution%20of%20IRIS%20SJI%201400%20%26Aring%3B."},{"type":"text","text":"IRIS%20observed%20the%20flare%20with%20a%20large%20sit-and-stare%20SJI%201400%20%26Aring%3B%20window%20and%201.7%20s%20cadence.%20Figure%201%20presents%20snapshots%20of%20the%20SJI%20evolution.%20Examining%20the%20light%20curve%20and%20HMI%20LOS%20magnetic%20flux%20of%20each%20region%2C%20we%20see%20the%20two%20ribbons%20brighten%20cotemporally%2C%20tracing%20equal%20magnetic%20flux%20throughout%20their%20evolution.%20We%20therefore%20imagine%20a%20single%20flux%20tube%20passing%20from%20one%20ribbon%20to%20the%20other%2C%20containing%20the%20reconnection%20regions%20within%20it.%20%20Jeffrey%20et%20al.%20%282018%29%20examine%20the%20spectral%20evolution%20of%20the%20east%20ribbon%2C%20finding%20a%20steep%20rise%20in%20Si%20IV%201402.77%20%26Aring%3B%20nonthermal%20velocity%20%28a%20signature%20of%20plasma%20turbulence%29%20preceding%20the%20rise%20in%20Si%20IV%20intensity%20%28flare%20onset%29.%20The%20slit%20position%20can%20be%20seen%20as%20a%20bright%20vertical%20streak%20in%20Figure%201.%0A%0AWe%20track%20a%20centroid%20along%20each%20ribbon%2C%20measuring%20intensity%20variation%20as%20they%20evolve.%20Intensity%20along%20the%20ribbons%20are%20measured%20for%20every%20time%20step%2C%20producing%20the%20intensity%20stack%20plots%20in%20Figure%202%20%28left%29.%20We%20calculate%20the%20FFT%20for%20each%20cross-section%2C%20calculating%20the%20power%20of%20different%20spatial%20scales%20along%20the%20flare%20ribbons.%20We%20combine%20each%20spatial%20FFT%20into%20a%20single%20stack%20plot%2C%20also%20in%20Figure%202%20%28right%29."},{"type":"image","file":"","url":"nuggetvideos/2022/02/24/pod_polito_vanessa_2022-02-24T21%3A30%3A07.698Z/IRIS_nugget_fig2.jpg","hash":"985c6120622e411e90f1c795d9fff4f2","mimeType":"image/jpeg","caption":"Figure%202%20%E2%80%93%20Left%3A%20ribbon%20intensity%20stack%20plot.%20Right%3A%20spatial%20scale%20power%20stack%20plot%2C%20normalized%20at%20each%20spatial%20scale.%20These%20plots%20are%20for%20the%20east%20ribbon%20%28see%20paper%20for%20west%20ribbon%29."},{"type":"text","text":"In%20MHD%2C%20exponential%20growth%20at%20multiple%20spatial%20scales%20is%20a%20classical%20signal%20of%20plasma%20instability%20%28Priest%201985%29.%20We%20investigate%20growth%20at%20each%20spatial%20scale%20by%20taking%20horizontal%20cross-sections%20through%20the%20power%20spectrum%20in%20Figure%202.%20We%20determine%20the%20region%20of%20exponential%20growth%20at%20each%20scale%2C%20and%20fit%20an%20exponential%20curve%20to%20provide%20a%20growth%20rate%20and%20start%2Fend%20times%20of%20the%20exponential%20phase.%20%0A%20%0AWe%20plot%20the%20duration%20of%20exponential%20growth%20in%20Figure%203%20%28left%29.%20%20We%20see%20exponential%20growth%20start%20initially%20at%20a%20single%20spatial%20scale%2C%20before%20beginning%20at%20all%20other%20scales%20up%20to%2019%20s%20later.%20This%20is%20suggestive%20of%20a%20process%20at%20a%20specific%20spatial%20scale%20causing%20the%20growth%20at%20progressively%20shorter%20and%20longer%20scales%20through%20a%20cascade%20and%20inverse%20cascade.%20Detecting%20matching%20%28when%20scaled%29%20spatial%20scales%20in%20each%20ribbon%20provides%20confidence%20that%20processes%20are%20linked%20%E2%80%94%20both%20likely%20originating%20from%20instability%20processes%20at%20the%20reconnection%20site.%20Our%20observational%20constraints%20to%20compare%20with%20theory%20are%3A%0A1.%20%20E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href=\"https://ui.adsabs.harvard.edu/abs/2021ApJ...922..117F/abstract\">French, R. J., ApJ 922, 117 (2021)</a>","<a href=\"https://ui.adsabs.harvard.edu/abs/1986PhFl...29.1520B/abstract\">Biskamp, D., PhFl 29, 1520 (1986)</a>","<a href=\"https://ui.adsabs.harvard.edu/abs/2018SciA....4.2794J/abstract\">Jefferey, N. L. S., SciA 4, 2794 (2018)</a>","<a href=\"https://ui.adsabs.harvard.edu/abs/1985RPPh...48..955P/abstract\">Priest, E. R., RPPh 48, 955 (1985)</a>","<a href=\"https://ui.adsabs.harvard.edu/abs/2020MNRAS.491.4267T/abstract\">Tenerani A. and Velli M., MNRAS 491, 4267 (2020)</a>","<a href=\"https://ui.adsabs.harvard.edu/abs/2018PhRvL.121p5101D/abstract\">Dong, C., PhRvL 121, 165101 (2018)</a>","","","",""],"pubDate":"2022-03-11T19:51:21.82Z"}