IRIS Nugget
Welcome to the IRIS Science Nuggets: highlights of recent IRIS scientific results for the solar physics community.
{"id":"pod_polito_vanessa_2024-04-04T19:00:51.663Z","submitter":"Soumya Roy","author":"Soumya Roy [1,2] and Durgesh Tripathi [1]","status":"published","creation-date":"2024-04-04T19:00:51.689Z","last-modified-date":"2024-04-12T04:52:10.45Z","credit":"[1] Inter-University Centre for Astronomy and Astrophysics, [2] Harvard-Smithsonian Center for Astrophysics","title":"Evolution of Mg II Intensities during Solar Flares","contentBlocks":[{"type":"text","text":"The%20Mg%20II%20k%20and%20h%20line%20intensity%20ratios%20can%20be%20used%20to%20probe%20the%20characteristics%20of%20the%20plasma%20in%20the%20solar%20atmosphere.%20In%20optically%20thin%20conditions%2C%20the%20intensity%20ratio%20of%20the%20k%20to%20h%20line%20is%202%3A1%20and%20lower%20when%20the%20medium%20is%20optically%20thick%20%28Kerr%20et%20al.%202015%3B%20Levens%20%26amp%3B%20Labrosse%202019%29.%20Here%2C%20we%20study%20the%20evolution%20of%20the%20intensities%20ratios%20of%20the%20Mg%20II%20h%20and%20k%20lines%20during%20the%20evolution%20of%20three%20flares%2C%20viz.%2C%20C-class%2C%20M-Class%2C%20and%20X-class.%20We%20focus%20on%20the%20dependence%20of%20line%20ratios%20on%20the%20underlying%20magnetic%20field%20strength."},{"type":"image","file":"","url":"nuggetvideos/2024/04/04/pod_polito_vanessa_2024-04-04T19%3A00%3A51.663Z/iris_nugget.png","hash":"cb06cd859e3ecf417e23fcfbd724383f","mimeType":"image/png","caption":"Figure%201.%20IRIS%20SJI%202796%20%26Aring%3B%20observation%20of%20the%204th%20November%202015%20flare.%20The%20filament%20material%20erupts%2C%20and%20the%20primary%20ribbons%20move%20through%20the%20IRIS%20raster%20FOV.%20The%20longer%20ribbon%20sweeps%20through%20the%20SJI%20field%20of%20view%20towards%20the%20north-east."},{"type":"text","text":"The%20NOAA%20AR%2012443%20produced%20a%20multiribbon%20GOES%20class%20M3.7%20flare%20on%20November%204%202015%20that%20began%20%7E%2013%3A31%20UT%20and%20peaked%20at%20%7E13%3A52%20UT.%20IRIS%20observed%20the%20flare%20with%20coarse%2016-step%20raster%20with%2050s%20raster%20cadence.%20The%20X%20and%20C%20class%20flares%20were%20observed%20with%20coarse%208-step%20and%20dense%2016-step%20rasters%20with%20131s%20and%2033s%20raster%20cadence%20respectively.%20We%20use%20AIA%201600%20%26Aring%3B%20and%20SJI%201400%20%26Aring%3B%20observations%20to%20align%20the%20IRIS%20raster%20to%20HMI%20observations%20and%20make%20the%20plate%20scales%20same.%20We%20then%20artificially%20raster%20the%20HMI%20observations%20%28Fig.%202%29."},{"type":"image","file":"","url":"nuggetvideos/2024/04/04/pod_polito_vanessa_2024-04-04T19%3A00%3A51.663Z/iris_nugget.001.jpeg","hash":"a2b753e7b47e5598e0ab2e2301a2bae5","mimeType":"image/jpeg","caption":"Figure%202.%20Integrated%20intensity%20maps%20in%20Mg%20II%20h%20%28panel%20a%29%20and%20k%20%28panel%20b%20%29%20line.%20The%20corresponding%20coaligned%20and%20artificially%20rastered%20HMI%20LOS%20magnetic%20field%20map.%20The%20magenta%20and%20lime%20green%20contours%20in%20panel%20%28c%29%20show%20the%20contours%20of%20Mg%20II%20h%20%28panel%20%28a%29%29%20and%20k%20%28panel%20%28b%29%29%20intensity."},{"type":"text","text":"To%20investigate%20the%20time%20evolution%20of%20the%20intensity%20ratio%20and%20its%20relationship%20with%20the%20photospheric%20magnetic%20field%2C%20if%20any%2C%20we%20binned%20the%20spectra%20from%20flaring%20pixels%20by%20their%20magnetic%20field%20strength.%20We%20fitted%20a%20double%20Gaussian%20profile%20with%20a%20constant%20background%20to%20both%20Mg%20II%20k%20and%20h%20lines%20separately%20%28Fig.%203%29.%20This%20is%20done%20to%20avoid%20the%20effects%20of%20the%20background%20and%20the%20possible%20contribution%20of%20any%20other%20spectral%20feature.%20We%20compute%20the%20line%20intensities%20by%20integrating%20the%20fitted%20Gaussian.%20We%20follow%20the%20same%20procedure%20for%20all%20flares."},{"type":"image","file":"","url":"nuggetvideos/2024/04/04/pod_polito_vanessa_2024-04-04T19%3A00%3A51.663Z/apjad2a46f7_hr.jpg","hash":"3adba44dc33b2ad60e01e291fed7b5d8","mimeType":"image/jpeg","caption":"Figure%203.%20Fitted%20line%20profiles%20for%20the%20binned%20spectra%20for%20various%20magnetic%20field%20strengths%20from%20various%20times."},{"type":"text","text":"For%20the%20M%20class%20flare%2C%20the%20intensity%20ratios%20rise%20sharply%20during%20the%20impulsive%20phase%2C%20from%20%7E1.20%20to%20%7E1.28%20right%20before%20the%20soft%20X-ray%20flux%20peaks%20as%20seen%20from%20GOES%20and%20decrease%20rapidly%20thereafter%20to%20lower%20than%20preflare%20values%20%7E1.12%20%28Fig.%204%29.%20The%20evolution%20of%20the%20Mg%20II%20line%20intensity%20ratios%20are%20also%20very%20similar%20for%20various%20strengths%20of%20magnetic%20flux%20densities.%20The%20Mg%20II%20k-to-h-line%20intensity%20ratio%20behaves%20similarly%20for%20the%20C-class%20flare.%20It%20peaks%20during%20the%20impulsive%20phase%20%28k%2Fh%20%7E%201.12%29%20and%20reduces%20to%20preflare%20values%20%28k%2Fh%20%7E%201.09%29%20during%20the%20decay%20phase%20of%20the%20flare.%20The%20change%20in%20Mg%20II%20k-to-h-line%20intensity%20ratio%20is%20less%20prominent%20for%20this%20flare%20than%20the%20M-class%20event.%20Unlike%20the%20M%20and%20C%20class%20flare%2C%20we%20do%20not%20find%20any%20detectable%20change%20in%20the%20intensity%20ratio%20during%20the%20flare.%20About%20two%20to%20three%20data%20points%20show%20an%20enhancement%20in%20the%20ratio%2C%20which%20is%20much%20before%20the%20start%20of%20the%20flare."},{"type":"image","file":"","url":"nuggetvideos/2024/04/04/pod_polito_vanessa_2024-04-04T19%3A00%3A51.663Z/iris_nugget_2.jpg","hash":"a020b6f8a290d562443e798cdeee8dea","mimeType":"image/jpeg","caption":"Figure%204.%20Time%20evolution%20of%20the%20Mg%20II%20k-to-h-line%20intensity%20ratio%20obtained%20from%20averaged%20spectrum%20over%20the%20corresponding%20magnetic%20flux%20bin%20as%20labelled%20for%20the%20M%20%284th%20November%202015%20in%20panel%20a%29%2C%20C%20%283rd%20February%202015%20in%20panel%20b%29%20and%20X%20%2822nd%20October%202014%20in%20panel%20c%29%20class%20flare%2C%20respectively.%20For%20better%20visibility%2C%20the%2020.9%20-%20184.4%20G%20and%20348.9%20-%20513.3%20G%20points%20are%20offset%20by%2030%20s%20and%20-30%20s%2C%20respectively%2C%20for%20the%20M%20class%20flare.%20The%20overplotted%20red%20solid%20line%20displays%20the%201-8%20%26Aring%3B%20GOES%20X-ray%20light%20curve."},{"type":"text","text":"Mg%20II%20profiles%20vary%20significantly%20in%20shape%20and%20spatially%20within%20the%20flaring%20region%20%28Panos%20et%20al.%202018%3B%20Sainz%20Dalda%20%26amp%3B%20De%20Pontieu%202023%29.%20We%20show%20that%20the%20Mg%20II%20k-to-h-line%20intensity%20ratios%20change%20during%20flares.%20For%20the%20M-class%20and%20C-class%20flares%2C%20the%20ratio%20increases%20at%20the%20start%20of%20the%20flare%2C%20peaks%20approximately%20halfway%20in%20the%20impulsive%20phase%2C%20and%20shows%20a%20steep%20decline%20thereafter.%20The%20ratios%20fall%20even%20below%20the%20preflare%20conditions%20during%20the%20later%20stage%20of%20the%20flare.%20However%2C%20this%20behaviour%20is%20only%20observed%20in%20the%20M-%20and%20C-class%20flares%20and%20not%20in%20the%20X-class%20flare.%0AOur%20observations%20showed%20no%20correlation%20between%20the%20line%20intensity%20ratios%20and%20magnetic%20flux%20density.%20The%20line%20intensity%20ratio%20for%20different%20magnetic%20field%20strengths%20similarly%20affects%20the%20Mg%20II%20k%20and%20h%20lines.%0AKerr%20et%20al.%20%282015%29%20studied%20Mg%20II%20k-to-h-line%20intensity%20ratios%20and%20their%20time%20variation%20for%20individual%20pixels%20in%20the%20quiet%20Sun%20region%20and%20flaring%20locations.%20While%20they%20found%20no%20change%20in%20the%20ratios%20for%20the%20quiet%20Sun%20region%2C%20they%20noted%20that%20flaring%20pixels%20did%20show%20variations%20in%20the%20intensity%20ratios.%20They%20speculated%20that%20this%20might%20be%20due%20to%20differences%20in%20heating%20conditions%20in%20the%20non-flaring%20and%20flaring%20atmospheres.%20However%2C%20they%20did%20not%20observe%20any%20correlated%20change%20in%20the%20ratio%20with%20respect%20to%20the%20flare%20light%20curve.%0AOur%20results%20align%20with%20those%20obtained%20by%20Kerr%20et%20al.%20%282015%29%2C%20where%20we%20also%20find%20that%20the%20change%20in%20the%20ratio%20is%20highest%20during%20the%20impulsive%20phase%20of%20the%20flare%20and%20starts%20to%20decrease%20before%20the%20flare%20reaches%20its%20maximum%20in%20GOES.%20Such%20changes%20may%20indicate%20variation%20in%20the%20opacity%20of%20the%20local%20medium.%20In%20this%20scenario%2C%20the%20optical%20depth%20first%20decreases%20during%20the%20impulsive%20heating%20phase%20and%20starts%20to%20increase%20during%20the%20decay%20phase.%20While%20the%20decrease%20in%20the%20optical%20depth%20during%20the%20impulsive%20phase%20may%20be%20attributed%20to%20localised%20heating%20and%20chromospheric%20evaporation%2C%20the%20increase%20during%20the%20decay%20phase%20of%20the%20flare%20may%20be%20explained%20by%20condensation%20and%20downflows."}],"references":["<a href=\"https://ui.adsabs.harvard.edu/abs/2015A%26A...582A..50K/abstract\">Kerr, G. S., Simões, P. J. A., Qiu, J., & Fletcher, L. 2015, A&A, 582, A50</a>","<a href=\"https://ui.adsabs.harvard.edu/abs/2019A%26A...625A..30L/abstract\">Levens, P. J., & Labrosse, N. 2019, A&A, 625, A30</a>","<a href=\"https://ui.adsabs.harvard.edu/abs/2018ApJ...861...62P/abstract\">Panos, B., Kleint, L., Huwyler, C., et al. 2018, ApJ, 861, 62</a>","<a href=\"https://ui.adsabs.harvard.edu/abs/2023FrASS..1033429S/abstract\">Sainz Dalda, A., & De Pontieu, B. 2023, FrASS, 10, 1133429</a>","","","","","",""],"pubDate":"2024-04-12T16:20:41.211Z"}