IRIS Nugget
Welcome to the IRIS Science Nuggets: highlights of recent IRIS scientific results for the solar physics community.
{"id":"pod_polito_vanessa_2024-08-05T19:17:56.656Z","submitter":"Marcel F. Corchado Albelo","author":"Marcel F. Corchado Albelo [1, 2, 3], Maria D. Kazachenko [1, 2], Benjamin J. Lynch [4, 5]","status":"published","creation-date":"2024-08-05T19:17:56.687Z","last-modified-date":"2024-08-14T18:46:07.567Z","credit":"[1]Department of Astrophysical and Planetary Sciences, University of Colorado Boulder, [2] National Solar Observatory, [3] DKIST Ambassador, [4] Space Sciences Laboratory, University of California, [5] Department of Earth, Planetary, and Space Sciences, University of California, Los Angeles","title":"Inferring Fundamental Properties of the Flare Current Sheet Using Flare Ribbons: Oscillations in the Reconnection Flux Rates","contentBlocks":[{"type":"text","text":"Solar%20magnetic%20reconnection%20is%20understood%20to%20be%20the%20process%20by%20which%20energy%20is%20released%20during%20solar%20flares.%20The%20standard%20flare%20model%20successfully%20describes%20how%20magnetic%20reconnection%20drives%20energy%20transfer%20from%20the%20global%20reconstruction%20of%20the%20magnetic%20field%20into%20plasma%20heating%2C%20particle%20acceleration%2C%20bulk%20plasma%20motions%2C%20and%20radiation.%20Yet%2C%20this%20standard%20scenario%20does%20not%20describe%20the%20mechanism%20through%20which%20reconnection%20leads%20to%20non-thermal%20particle%20acceleration%2C%20and%20particularly%20the%20modulating%20signatures%20of%20flaring%20emission%20across%20many%20wavelengths%E2%80%94called%20quasi%20periodic%20pulsation%20%28QPPs%3B%20Nakariakov%20%26amp%3B%20Melnikov%202009%29.%20Included%20in%20the%20standard%20scenario%20are%20the%20flare%20ribbons%2C%20or%20footpoints%20of%20newly%20reconnected%20field%20lines%20on%20the%20lower%20solar%20atmosphere.%20In%20recent%20years%2C%20flare%20ribbons%20allowed%20the%20routine%20estimate%20of%20the%20reconnection%20flux%20by%20combining%20the%20area%20enclosing%20new%20flare%20ribbon%20kernels%20and%20measurements%20of%20the%20vertical%20component%20of%20the%20magnetic%20field.%20%20%0A%0AIn%20this%20paper%20%28Corchado%20Albelo%20et%20al.%202024%29%20we%20explore%20the%20oscillations%20in%20the%20rate%20of%20magnetic%20reconnection%20as%20a%20proxy%20of%20current%20sheet%20dynamics.%20Specifically%2C%20we%20focus%20on%20studying%20the%20QPPs%20observed%20in%20a%20sample%20of%2073%20flares%20with%20GOES%20X-ray%20classification%20above%20C-class.%20Additionally%2C%20we%20look%20at%20the%20morphological%20evolution%20of%20the%20flare%20ribbons%2C%20including%20both%20the%20large-scale%20evolution%2C%20and%20development%20of%20flare%20ribbon%20substructures%20as%20an%20indicator%20of%20potential%20current%20sheet%20dynamics%20%28Wyper%20%26amp%3B%20Pontin%202021%3B%20Naus%20et%20al.%202022%29."},{"type":"image","file":"","url":"nuggetvideos/2024/08/05/pod_polito_vanessa_2024-08-05T19%3A17%3A56.656Z/fine-structure-recrate.jpg","hash":"367e55e86dc3948e2bd10b25ba836f41","mimeType":"image/jpeg","caption":"Figure%201.%20Evolution%20of%20flare%20ribbon%20fine%20structure%20during%20an%20X1.6%20flare%20in%20AR%2012158%20using%20IRIS%201400%20%26Aring%3B%20SJI%20observations.%20%28a%29%20IRIS%201400%20%26Aring%3B%20cumulative%20flare%20ribbon%20mask%20evolution%20over%20HMI%20Br%20.%20%28b%29%20IRIS%20SJI%20observations%20of%20flare%20ribbons%20during%20the%20reconnection-rate%20maximum%20at%20t%20%E2%89%88%2017%3A24%20UTC.%20%28c%29%20Flare%20ribbons%20during%20the%20decay%20of%20the%20second%20largest%20reconnection-rate%20burst%20at%20t%20%E2%89%88%2017%3A29%20UTC.%20%28d%29%20Flare%20ribbons%20during%20a%20later%20reconnection-rate%20burst%20at%20t%20%E2%89%88%2017%3A32%20UTC.%20%28e%29%20Unsigned%20reconnection%20flux%20%28black%29%20and%20its%20rate%20%28gray%29.%20The%20dotted%20vertical%20gray%20and%20solid%20vertical%20black%20lines%20represent%20the%20reconnection-rate%20peaks%20and%20the%20IRIS%20observation%20frames%20shown%20in%20panels%20%28b%29%E2%80%93%28d%29%2C%20respectively."},{"type":"text","text":"Figure%201%20illustrates%20how%20we%20combine%20flare%20ribbons%20observations%20from%20the%20Interface%20Region%20Imaging%20Spectrograph%20%28IRIS%29%20Slit%20Jaw%20Imager%20%28SJI%29%201400%20%26Aring%3B%20and%20the%20Solar%20Dynamics%20Observatory%20%28SDO%29%2C%20for%20the%202014-09-10%20X-class%20flare%2C%20to%20estimate%20the%20reconnection%20flux%20and%20rate%20%28Kazachenko%20et%20al.%202017%29%2C%20and%20its%20association%20to%20the%20global%20and%20substructure%20flare%20ribbon%20evolution.%20Our%20result%20suggests%20that%20the%20large-scale%20evolution%20of%20the%20flare%20ribbon%20is%20comprised%20of%20moments%20in%20which%20the%20structure%20intermittently%20expands%20and%20includes%20newly%20reconnected%20field%20lines.%20This%20results%20in%20a%20bursty%20reconnection%20rate%20profile%20which%20is%20like%20the%20QPPs%20regularly%20observed%20in%20Hard-X-ray%20emission%20observations.%20Although%20we%20do%20not%20address%20the%20role%20or%20contribution%20of%20the%20flare%20ribbon%20substructure%20to%20the%20reconnection%20rate%20bursts%20we%20find%20evidence%2C%20in%20IRIS%20SJI%20observations%2C%20that%20substructure%20co-develops%20with%20the%20reconnection%20rate%20QPPs%20in%208%20of%20our%2073%20events.%20Figure%202%20shows%2010%20examples%20from%20the%2073%20flares%20with%20observed%20QPPs%20in%20the%20reconnection%20rate%20%28from%20the%20flare%20ribbon%20connected%20to%20each%20magnetic%20polarity%29%20and%20Soft-X-ray%20emission%20rates%20and%20HXR%20emission."},{"type":"image","file":"","url":"nuggetvideos/2024/08/05/pod_polito_vanessa_2024-08-05T19%3A17%3A56.656Z/recrateosc.jpg","hash":"cae11da27b0921d02795354c53951ac1","mimeType":"image/jpeg","caption":"Figure%202.%20Ten%20example%20flares%20with%20oscillations%20%28QPPs%29%20in%20the%20reconnection%20rates%20and%20X-ray%20lightcurves.%20Panels%20%28a%29%E2%80%93%28e%29%20and%20%28k%29%E2%80%93%28o%29%20show%20reconnection%20fluxes%20%28crosses%29%20and%20reconnection%20flux%20rates%20%28triangles%29%20where%20red%20and%20blue%20colors%20correspond%20to%20positive%20and%20negative%20polarities%2C%20respectively.%20Panels%20%28f%29%E2%80%93%28j%29%20and%20%28p%29%E2%80%93%28t%29%20show%20Fermi%20HXR%20and%20GOES%20SXR%20rate%E2%80%AFlightcurves."},{"type":"text","text":"Qualitative%20examination%20of%20the%20QPP%20profiles%20in%20Figure%202%20suggest%20similar%20periods%20and%20simultaneity%20between%20the%20low%20frequency%20modulations%20on%20the%20reconnection%20rates%20and%20X-ray%20emission%2Frates.%20To%20quantify%20the%20similitude%20of%20the%20QPP%20characteristics%2C%20first%20we%20use%20the%20wavelet%20transform%20to%20identify%20the%20dominating%20oscillation%20modes%20in%20our%20time%20series%20%28Torrence%20%26amp%3B%20Compo%201998%29.%20Figure%203%20shows%20the%20results%20of%20applying%20the%20wavelet%20transform%20on%20the%20detrended%20HXR%2C%20SXR%20rate%2C%20and%20reconnection%20rates%20for%20an%20M-class%20flare%20observed%20on%202015-11-04.%20The%20results%20show%20that%20for%20this%20flare%20the%20X-ray%20QPPs%20have%20a%20higher%20frequency%20than%20the%20reconnection%20rate%20QPPs."},{"type":"image","file":"","url":"nuggetvideos/2024/08/05/pod_polito_vanessa_2024-08-05T19%3A17%3A56.656Z/wavelet_rec_hxr.jpg","hash":"829bf42b7a917372c7a9c1528a572872","mimeType":"image/jpeg","caption":"Figure%203.%20Wavelet%20and%20Fourier%20power%20spectra%20for%20X-ray%20fluxes%20and%20reconnection%20rate%20for%20the%20M3.7%202015%20November%204%20flare.%20Panel%20%28a%29%3A%20the%20detrended%20fluctuations%20in%20the%20Fermi%2025%E2%80%9350%20keV%20emission%20are%20shown%20on%20the%20top%20panel%2C%20its%20wavelet%20transform%20below%20it%2C%20and%20average%20wavelet%20power%20and%20Fourier%20power%20on%20the%20right.%20Panel%20%28b%29%3A%20fluctuation%20in%20the%20GOES%201%20%E2%88%92%208%20%26Aring%3B%20emission%20rate%20following%20the%20same%20layout%20as%20in%20%28a%29.%20Panel%20%28c%29%3A%20fluctuations%20in%20the%20magnetic%20reconnection%20rate%20with%20the%20same%20layout%20as%20in%20%28a%29%20and%20%28b%29.%20The%20red-to-yellow%20contours%20on%20the%20wavelet%20transform%20maps%20correspond%20to%20areas%20where%20wavelet%20power%20exceeds%20the%2095%25%20colored%20noise%20level."},{"type":"text","text":"Applying%20the%20Wavelet%20transform%20to%20the%20X-ray%20and%20reconnection%20rate%20QPPs%20for%20all%2073%20events%20allows%20us%20to%20evaluate%20the%20statistical%20relationship%20between%20the%20modulations.%20Although%20we%20find%20no%20statistical%20correlation%20between%20the%20reconnection%20rate%20and%20HXR%20QPPs%2C%20the%20distributions%20of%20periodicities%20are%20mostly%20contained%20within%20their%20mean%20values.%20Figure%204%20shows%20that%20the%20average%20HXR%20modulations%20have%20periods%20of%201.5%20minutes%2C%20while%20the%20reconnection%20rates%20have%20an%20average%20period%20of%202.5%20minutes.%20Due%20to%20discrepancies%20in%20the%20temporal%20cadence%20of%20the%20observations%20%28X-ray%20observations%20have%20at%20least%20six%20times%20greater%20cadence%29%20the%20periods%20can%20be%20interpreted%20as%20being%20similar.%20Therefore%20suggesting%20that%20the%20QPPs%20have%20a%20common%20driving%20mechanism%20involving%20bursty%20particle%20acceleration%20episodes%20and%20intermittent%20magnetic%20reconnection."},{"type":"image","file":"","url":"nuggetvideos/2024/08/05/pod_polito_vanessa_2024-08-05T19%3A17%3A56.656Z/osc_stats.jpg","hash":"4f12f6f40ed489fa838a568cf8e97c14","mimeType":"image/jpeg","caption":"Figure%204.%20Periods%20of%20QPPs%E2%80%AFin%20HXR%20emission%20%28from%20Fermi%20GBM%29%20vs.%20periods%20of%20QPPs%20in%20unsigned%20magnetic%20reconnection%20rates%20for%2073%20flares.%20Panels%20%28a%29%E2%80%93%28e%29%20correspond%20to%20the%20following%20X-ray%20energy%20bands%3A%20%28a%29%208%E2%80%9315%20keV%2C%20%28b%29%2015%E2%80%9325%20keV%2C%20%28c%29%2025%E2%80%9350%20keV%2C%20%28d%29%2050%E2%80%93100%20keV%2C%20and%20%28e%29%20100%E2%80%93300%20keV.%20QPP%E2%80%AFperiods%20have%20been%20identified%20using%20wavelet%20transform.%20The%20large%20circles%20represent%20the%20flares%20with%20periods%20that%20match%20up%20to%2030%25%20between%20the%20original%20time%20series%2C%20and%20the%20background%20subtracted%20time%20series.%20The%20yellow%20stars%20show%20case%20studies%20illustrated%20in%20the%20paper."},{"type":"text","text":"In%20summary%2C%20for%20the%20first%20time%20we%20find%20that%20magnetic%20reconnection%2C%20as%20described%20by%20reconnection%20rates%20derived%20from%20flare%20ribbons%2C%20occurs%20in%20bursts%20which%20are%20described%20as%20oscillations%20with%20periods%20ranging%20from%201-5%20minutes%2C%20with%20an%20average%20of%202.5%20minutes.%20Available%20co-temporal%20IRIS%20SJI%20observations%20provides%20evidence%20of%20flare%20ribbon%20substructure%20developing%20during%20the%20same%20time%20as%20the%20reconnection%20rate%20QPPs.%20Co-temporal%20QPP%20bursts%20in%20the%20reconnection%20rates%20and%20HXR%20emission%20provide%20evidence%20of%20oscillatory%20process%20in%20the%20reconnection%20region.%20Our%20findings%20of%20co-temporal%20flare%20ribbon%20fine-structure%20and%20bursty%20episodes%20of%20the%20reconnection%20rate%20and%20X-ray%20emission%20suggest%20that%20the%20mechanism%20involved%20in%20generating%20these%20minute%20long%20modulations%20is%20related%20to%20the%20evolution%20and%20dynamics%20of%20flare%20current%20sheet%20plasmoids%20%28Uzdensky%202010%3B%20Lynch%20et%20al.%202016%3B%20Guidoni%20et%20al.%202022%29."}],"references":["<a 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