{"id":"pod_polito_vanessa_2024-11-22T21:36:32.807Z","submitter":"Marta Garcia Rivas","author":"M. García-Rivas[1,2], J. Kasparová[1], A. Berlicki[1,3], M. Svanda[1,2], J. Dudík[1], D. Ctvrtecka[4], M. Zapiór[1], W. Liu[1], M. Sobotka[1], M. Pavelková[1], and G. G. Motorina[1,*]. [1]Astronomical Institute of the Czech Academy of Sciences [2]Astronomical Institute of Charles University [3]Center of Scientific Excellence - Solar and Stellar Activity, University of Wroclaw [4]Christian Doppler Grammar School [*]Central Astronomical Observatory at Pulkovo of Russian Academy of Sciences","status":"published","creation-date":"2024-11-22T21:36:32.856Z","last-modified-date":"2024-12-12T14:23:39.331Z","credit":"","title":"Flare heating of the chromosphere: Observations of flare continuum from GREGOR and IRIS","contentBlocks":[{"type":"text","text":"On%202022%2C%20May%204%2C%20an%20M5.7%20flare%20occurred%20in%20the%20active%20region%20NOAA%2013004%2C%20which%20was%20the%20target%20of%20a%20coordinated%20campaign%20between%20IRIS%2C%20GREGOR%2C%20Hinode%2C%20and%20ground-based%20instruments%20located%20at%20the%20Ond%C5%99ejov%20observatory.%20For%20the%20first%20time%2C%20IRIS%20and%20GREGOR%20co-observed%20the%20preflare%2C%20impulsive%2C%20and%20gradual%20phase%20of%20a%20solar%20flare.%20The%20current%20analysis%20%28Garc%26iacute%3Ba-Rivas%20et%20al.%202024%29%20was%20inspired%20by%20previous%20studies%20focused%20on%20UV%20and%20optical%20flare%20continuum%20enhancements.%20Our%20data%20are%20unique%20in%20UV%20wavelength%20coverage%20and%20temporal%20resolution.%20Co-spatial%20observations%20in%20several%20optical%20wavelengths%20obtained%20with%20the%20High-resolution%20Fast%20Imager%20%28HiFI%2B%29%20complement%20the%20dataset.%20Figure%201%20provides%20an%20overview%20of%20the%20M-flare%20as%20captured%20by%20instruments%20that%20participated%20in%20the%20campaign%20and%20context%20images."},{"type":"image","file":"","url":"nuggetvideos/2024/11/22/pod_polito_vanessa_2024-11-22T21%3A36%3A32.807Z/aa51219-24-fig1_double.jpg","hash":"c97882bf02b845b003a596001336d419","mimeType":"image/jpeg","caption":"Fig.%201.%20Overview%20of%20the%202022%20May%204%20M5.7%E2%80%93class%20flare%20as%20observed%20by%20multiple%20instruments.%20Panel%20a%20shows%20the%20GOES%20X-ray%20light%20curve%20of%20the%20flare.%20Panels%20b%E2%80%93g%20show%20the%20context%20SDO%2FAIA%20and%20SDO%2FHMI%20observations%20at%2008%3A52%3A45%20and%2008%3A57%3A45%20UT%2C%20denoted%20by%20vertical%20lines%20in%20panel%20a.%20Panel%20g%20includes%20the%20contours%20of%20the%20polarities%20%28positive%20in%20red%20and%20negative%20in%20blue%29%20from%20panel%20d.%20The%20FOVs%20of%20the%20HiFI%2B2%20and%20IRIS%2FSJI%20instruments%20are%20indicated%20in%20panel%20f%20%28only%20IRIS%2FSJI%20FOV%20in%20panel%20d%29%2C%20and%20the%20corresponding%20observations%20are%20shown%20in%20panels%20i%E2%80%93l%2C%20with%20the%20location%20of%20the%20IRIS%20slit%20indicated%20and%20the%20HiFI%2B%20images%20resampled%20to%20the%20IRIS%20resolution%20and%20FOV.%20The%20red%20arrows%20in%20panels%20d%20and%20i%20point%20to%20the%20location%20of%20pixel%20No.%2053.%20Ond%C5%99ejov%20ground-based%20observations%20from%20the%20spectrographs%20FICUS%20and%20HSFA-2%20and%20the%20Solar%20Patrol%20Service%20are%20shown%20in%20panels%20m%E2%80%93o%2C%20respectively.%20The%20black%20line%20in%20panel%20n%20indicates%20the%20HSFA-2%20slit%20position."},{"type":"text","text":"IRIS%20observed%20in%20sit-and-stare%20mode%20with%20a%20temporal%20cadence%20of%20%7E3s.%20The%20slit-jaw%20images%20were%20recorded%20in%20the%202832%26Aring%3B%20channel%2C%20with%20a%20FOV%20of%2060%E2%80%9D%26times%3B62%E2%80%9D.%20In%20this%20work%2C%20we%20focused%20on%20the%20analysis%20of%20the%20full%20read-out%20of%20the%20NUV%20spectra.%20We%20found%20flare%20continuum%20enhancement%20in%20pixel%20No.%2053%2C%20where%20the%20slit%20captured%20a%20flare%20kernel%20located%20at%20the%20edge%20of%20a%20pore%20%28Fig%202%29.%20%0A%0ASpectral%20ranges%20were%20delimited%20to%20investigate%20the%20flare%20line%20emission%20%28bands%20D%20and%20E%29%20and%20the%20flare%20continuum%20enhancement%20%28bands%20A%2C%20B%2C%20C%29.%20Bands%20A%20and%20B%20were%20defined%20by%20Joshi%20et%20al.%20%282021%29%20and%20Heinzel%20%26amp%3B%20Kleint%20%282014%29%2C%20respectively.%20We%20defined%20band%20C%2C%20a%20band%20that%20does%20not%20contain%20any%20spectral%20line%20and%20is%20located%20far%20from%20Mg%E2%80%AFII%20lines%2C%20where%20the%20contribution%20from%20their%20far%20wings%20is%20negligible.%20Lightcurves%20of%20the%20bands%20at%20pixel%20No.%2053%20are%20plotted%20in%20Fig.%203."},{"type":"image","file":"","url":"nuggetvideos/2024/11/22/pod_polito_vanessa_2024-11-22T21%3A36%3A32.807Z/aa51219-24-fig2.jpg","hash":"4bc610eae649a9b23b8e43efe8beb1ac","mimeType":"image/jpeg","caption":"Fig.%202..%20IRIS%20NUV%20spectra%20recorded%20at%20the%20time%20of%20maximum%20continuum%20emission%20%2808%3A57%3A45%20UT%29%20along%20the%20full%20IRIS%20slit%20with%20colour%20boxes%20marking%20the%20spectral%20ranges%20%28A%2C%20B%2C%20C%2C%20D%2C%20and%20E%29%20used%20for%20the%20light%20curve%20plots%20and%20for%20the%20continuum%20analysis.%20The%20right%20image%20iis%20a%20synchronous%20IRIS%20SJI%20snapshot%20with%20a%20horizontal%20white%20line%20marking%20the%20height%20of%20pixel%20No.%2053."},{"type":"text","text":"Flare%20spectra%20and%20images%20were%20recorded%20at%20the%20GREGOR%20telescope%20as%20well.%20During%20the%20observing%20period%2C%20the%20seeing%20was%20mediocre%20but%20reasonably%20stable.%20In%20this%20work%2C%20we%20only%20investigated%20images%20captured%20by%20HiFI%2B%2C%20which%20is%20composed%20of%20three%20sets%20of%20two%20synchronised%20cameras%3A%20HiFI%2B1%20%28G-band%204307%26Aring%3B%20and%20blue%20continuum%204506%26Aring%3B%20filter%29%2C%20HiFI%2B2%20%28H-alpha%206563%26Aring%3B%20narrow-%20and%20broadband%20filters%29%2C%20and%20HiFI%2B3%20%28TiO%207058%26Aring%3B%20and%20CaII%20H%203968%26Aring%3B%20filters%29.%20All%20cameras%20have%20an%20acquisition%20rate%20of%20milliseconds%2C%20and%20pixel%20scales%20of%200.050%E2%80%9D%20and%20smaller.%20HiFI%2B%20images%20were%20aligned%20and%20resampled%20to%20the%20IRIS%2FSJI%20frame%20closest%20in%20time.%20TiO%20and%20blue%20continuum%20lightcurves%20at%20pixel%20No.%2053%20provide%20the%20evolution%20of%20the%20flare%20continuum%20in%20the%20optical%20range%20%28Fig.%203%29.%20%0A%0A%0AAdditionally%2C%20we%20employed%20SDO%2FHMI%20synoptic%20filtergrams%20%28level%201%20data%29%2C%20that%20were%20aligned%20to%20IRIS%2FSJI.%20We%20focused%20on%20the%20outer%20positions%20of%20the%20Fe%20I%206173%26Aring%3B%20line%2C%20far%20in%20the%20spectral-line%20wings%2C%20to%20separate%20the%20continuum%20enhancement%20from%20a%20possible%20brightening%20in%20the%20spectral%20line.%20We%20interpolated%20both%20filtergram%20series%20to%20a%20uniform%20series%20with%20a%20cadence%20of%2030s."},{"type":"image","file":"","url":"nuggetvideos/2024/11/22/pod_polito_vanessa_2024-11-22T21%3A36%3A32.807Z/aa51219-24-fig2_double.jpg","hash":"72db5320e6a1742ae1453f4760f70208","mimeType":"image/jpeg","caption":"Fig.%203.%20Light%20curves%20in%20several%20wavelength%20bands%20corresponding%20to%20spatially%20integrated%20emission%20%28panel%20a%29%20and%20pixels%20co-spatial%20with%20the%20pixel%20No.%2053%20along%20the%20IRIS%20slit%20%28panels%20b%E2%80%93e%29.%20Panel%20a%3A%20Konus%20count%20rate%20in%20the%20G1%20channel%20and%20GOES%20time%20derivative.%20Panel%20b%3A%20Emission%20in%20several%20SDO%2FAIA%20filters%20with%20the%201600%20%26Aring%3B%20filter%20data%20scaled%20by%20ten%20for%20plotting%20purposes.%20Panels%20c%20and%20d%3A%20calibrated%20intensity%20averaged%20in%20the%20IRIS%20spectral%20bands%20A%2C%20B%2C%20C%20%28panel%20c%3B%20continuum%20emission%29%2C%20D%2C%20and%20E%20%28panel%20d%3B%20line%20emission%29.%20Panel%20e%3A%20Emission%20relative%20to%20the%20quiet-Sun%20values%20in%20several%20GREGOR%20HiFI%2B%20filters.%20The%20preflare%20time%20interval%20for%20evaluating%20the%20IRIS%20C%20band%20preflare%20emission%20is%20delimited%20by%20two%20solid%20vertical%20lines%20in%20panel%20c%29.%20The%20vertical%20dotted%20line%20indicates%20the%20start%20of%20the%20last%20HXR%20pulse."},{"type":"text","text":"Based%20on%20the%20method%20employed%20by%20Heinzel%20et%20al.%20%282017%29%2C%20the%20ratio%20of%20the%20intensity%20excess%20with%20respect%20to%20a%20preflare%20state%20at%20different%20wavelengths%20is%20a%20function%20of%20temperature%2C%20%5Cbegin%7Bequation%7Df%28T%29%20%3D%20%CE%94I_%7B%5Cmathrm%7BOpt%7D%7D%2F%CE%94I_%7B%5Cmathrm%7BUV%7D%7D%20%5Cend%7Bequation%7D.%20This%20method%20assumes%20that%20any%20excess%20of%20continuum%20emission%20is%20due%20to%20hydrogen%20recombination%20processes.%20Therefore%2C%20the%20mean%20temperature%20of%20the%20layer%20where%20the%20continuum%20enhancement%20originates%20can%20be%20calculated%20by%20comparing%20the%20observational%20%5Cbegin%7Bequation%7D%20%CE%94I_%7B%5Cmathrm%7BOpt%7D%7D%2F%CE%94I_%7B%5Cmathrm%7BUV%7D%7D%20%5Cend%7Bequation%7D%20to%20the%20theoretical%20%20%5Cbegin%7Bequation%7D%20f%28T%29%20%5Cend%7Bequation%7D.%20%0A%0AWe%20converted%20all%20intensities%20into%20physical%20units%20and%20estimated%20the%20continuum%20enhancement%20in%20IRIS%20band%20C%2C%20HiFI%2B%20blue%20continuum%20and%20TiO%2C%20and%20HMI.%20Since%20no%20obvious%20continuum%20enhancement%20was%20detected%20by%20either%20HiFI%2B%20or%20HMI%20at%20the%20time%20of%20the%20flare%2C%20the%20enhancement%2C%20if%20any%2C%20had%20to%20be%20lower%20than%20the%20fluctuations%20of%20non-flare%20origin%20%28seeing%29%20or%20instrument%20sensitivity%20%28HMI%29.%20Therefore%2C%20only%20an%20upper%20limit%20on%20the%20possible%20continuum%20excess%20could%20be%20determined%2C%20giving%20us%20a%20lower%20limit%20on%20the%20mean%20temperature%20%28Fig.%204%29.%20The%20analysis%20of%20the%20regions%20co-spatial%20with%20pixel%20No.%2053%20in%20IRIS%20slit%20led%20to%20a%20lower%20limit%20on%20the%20temperature%20of%20%5Cbegin%7Bequation%7D%E2%88%BC%283%E2%80%9315%29%26times%3B10%5E3%5Cend%7Bequation%7DK%20in%20the%20flaring%20chromospheric%20layers."},{"type":"image","file":"","url":"nuggetvideos/2024/11/22/pod_polito_vanessa_2024-11-22T21%3A36%3A32.807Z/aa51219-24-fig8_double.jpg","hash":"50b19459481d30b34bf3ccb04abb4e15","mimeType":"image/jpeg","caption":"Fig.%204.%20Time%20evolution%20of%20%28a%29%20the%20determined%20intensity%20enhancement%20at%20%5Cbegin%7Bequation%7D%5Clambda_%7B%5Cmathrm%7BIRIS%7D%7D%20%5Cend%7Bequation%7D%20and%20the%20upper%20limits%20at%20%5Cbegin%7Bequation%7D%5Clambda_%7B%5Cmathrm%7Bblue%7D%7D%20%5Cend%7Bequation%7D%2C%20%5Cbegin%7Bequation%7D%5Clambda_%7B%5Cmathrm%7BHMI%7D%7D%20%5Cend%7Bequation%7D%20and%20%5Cbegin%7Bequation%7D%5Clambda_%7B%5Cmathrm%7BTiO%7D%7D%20%5Cend%7Bequation%7D%3B%20%28b%29%20the%20measured%20ratios%20for%20the%20three%20different%20wavelengths%20at%20the%20optical%20range%3A%20%5Cbegin%7Bequation%7D%5Clambda_%7B%5Cmathrm%7Bblue%7D%7D%20%5Cend%7Bequation%7D%2C%20%5Cbegin%7Bequation%7D%5Clambda_%7B%5Cmathrm%7BHMI%7D%7D%20%5Cend%7Bequation%7D%20and%20%5Cbegin%7Bequation%7D%5Clambda_%7B%5Cmathrm%7BTiO%7D%7D%20%5Cend%7Bequation%7D%3B%20%28c%29%20the%20lower%20limit%20on%20the%20mean%20temperature%20as%20determined%20from%20%5Cbegin%7Bequation%7D%20%CE%94I_%7B%5Cmathrm%7BTiO%7D%7D%2F%CE%94I_%7B%5Cmathrm%7BIRIS%7D%7D%20%5Cend%7Bequation%7D%20and%20%5Cbegin%7Bequation%7D%20%CE%94I_%7B%5Cmathrm%7BHMI%7D%7D%2F%CE%94I_%7B%5Cmathrm%7BIRIS%7D%7D%20%5Cend%7Bequation%7D."},{"type":"text","text":"This%20study%20demonstrates%20the%20rich%20diagnostic%20potential%20that%20multi-instrument%20and%20multi-wavelength%20flare%20campaigns%20have.%20Our%20findings%20support%20previous%20indications%20that%20continuum%20enhancement%20is%20also%20present%20in%20confined%20flares%20and%20in%20flaring%20areas%20of%20weak%20emission%20and%20that%20the%20associated%20temperature%20varies%20on%20very%20short%20timescales."}],"references":["<a href=\"https://ui.adsabs.harvard.edu/abs/2024A%26A...690A.254G/abstract\">García-Rivas, M., Kasparová, J., Berlicki, A., Svanda, M., Dudík, J., Ctvrtecka, D., Zapiór, M., Liu, W., Sobotka, M., Pavelková, M., and Motorina, G.G., A&A 690, A254 (2024)</a>","<a href=\"https://ui.adsabs.harvard.edu/abs/2021A%26A...654A..31J/abstract\">Joshi, R., Schmieder, B., Heinzel, P., Tomin, J., Chandra, R., and Vilmer, N., A&A 654, A31 (2021)</a>","<a href=\"https://ui.adsabs.harvard.edu/abs/2014ApJ...794L..23H/abstract\">Heinzel, P., and Kleint, L., ApJ 794, L23 (2014)</a>","<a href=\"https://ui.adsabs.harvard.edu/abs/2017ApJ...847...48H/abstract\">Heinzel, P., Kleint, L., Kasparová, J., and Krucker, S., ApJ 847, 48 (2017)</a>","","","","","",""],"pubDate":"2024-12-12T14:21:46.183Z"}