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Spatial deconvolution and inversion of 2D spectropolarimetric data

Spatial deconvolution and inversion of 2D spectropolarimetric data. Asensio Ramos Ruiz Cobo Instituto de Astrofísica de Canarias. The Earth atmosphere strongly perturbs the ability to get good images and polarimetric data.

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Spatial deconvolution and inversion of 2D spectropolarimetric data

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  1. Spatialdeconvolutionand inversion of 2D spectropolarimetricdata • Asensio Ramos • Ruiz Cobo • Instituto de Astrofísica de Canarias

  2. TheEarthatmospherestronglyperturbstheabilityto getgoodimages and polarimetric data

  3. Buteventhediffraction at thetelescopemodifiestheobservations

  4. Motivation Develop a fastmethodtoinvertspatiallydeconvolved spectro-polarimetricobservationsfromspace

  5. Imagedeconvolution Imageformation in a linear system Imagedeconvolution as a probabilisticproblem ForGaussiannoise Richardson-Lucy algorithm (Richardson 1972, Lucy 1974)

  6. Problemswithimagedeconvolution • Spectropolarimetric data has to be deconvolvedfrequencybyfrequency • Thesignal-to-noise ratio in manyfrequenciesisverysmall • Maximum-likelihooddeconvolutionisverysensitivetonoise • Use a prior forimagestodiminishtheeffect of noise

  7. Our prior forthesignal Wewritethe Stokes profiles as a linear combination in anorthonormalbasis Thelinearity of theimageformation leads to Projectingonthebasis and usingtheorthonormality of thebasis, the deconvolution reduces todeconvolvingseveral ‘projectedimages’

  8. Original Deconvolved

  9. Original Deconvolved

  10. Advantages • Projectedimages are almostnoiseless, so thatthemaximum-likelihooddeconvolutionbehavesmuchbetter • Ifthebasis set issufficiently general, no relevantinformationislost inthetruncation we use anempirical PCA basis • Thedeconvolutionprocessiscomputationally simple, unlikeotherapproacheslikethat of van Noort (2012) • Nowanyinversionscheme can be appliedwithoutstray-light correction

  11. Thecontrast in thequietregionsincreases fromfrom 6.3% to11.7%

  12. Deconvolved Original

  13. Penumbra – Magneto-convection in inclinedmagneticfield? • MHD simulations reproduce penumbra as magneto-convection in inclinedmagneticfielc (Rempel et al. 2009 a,b) • Downwardvelocitieswithinversepolaritiesshould be observedalongtheborders of penumbralfilaments • Convectivedownflow Scharmer et al. (2011), Scharmer & Henriqes (2012), Joshi et al. (2011) • Reversed flux in outer penumbra  Westendorp Plaza et al. (1997,2001)del Toro Iniesta et al. 2001 • Indirectindications in Stokes V  Franz (2011)

  14. Inversionspresentlargerconstrast in allquantities

  15. Reversedpolarity in theinner and outer penumbra

  16. Downflow+reversepolarity (wrt umbra)

  17. Afterdeconvolution Beforedeconvolution (2-component inversion)

  18. Conclusions • Fastregularizareddeconvolutionavailable • Dispersed light almostdisappears • Inversion of 2D data • Clear signatures of downflowing material withoppositepolarity in the penumbra

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