INAF Osservatorio Astrofisico di Arcetri Firenze, Italy First Results from IBIS: Photospheric and Chromospheric Structure and Dynamics Katja Janßen Gianna Cauzzi, Ambretta Falchi JENAM Conference The many scales in the universe 13. September 2004 Data Characteristics Investigated Line: Fe I 7090 Å The data consists of 2dim Spectrograms (80' ' diameter), scanned in wavelengths (with a stepwidths of 26 mÅ) => Datacube with two spatial and one spectral axis The FPIs are mounted in collimated beam: => Blueshift of wavelength over the FOV (max. 60 mÅ, at imagerim) Complete dataset shows a timeseries of 30 min (with 30 s interval) Photo of IBIS at the Dunn Solar Telescope, two big boxes contain the FPIs, between them the filterwheel is seen. Data Reduction We do: Cut imagesize to 50' ' x 50' ' Bin by a factor of 2 => Pixelsize: 0.16' ' This is done to speed up the calculations. Flatfield and Dark correction The flatfield scan contains the spectral line as the data. This spectral information has to be deleted, in order not to cancel the line in the data with the flatfielding. This is done by dividing the flatfield scan by an average flatfield profile (adding up the blueshiftcorrected profiles), for each pixel shifted to the wavelengths of its original profile. Image Motion Images in one scan are correlated and shifted in x,y. For each wavelength position also the blueshift map is shifted and saved. Blueshift of Wavelength The correction of the wavelength shifts is not applied directly, in order to avoid interpolations. Instead the blueshift is taken care of with the velocity calculations. Data Reduction We get: Continuum Images Center of Gravity Velocities Bisector Velocities Line Core Velocities FWHM of the Line To the timeseries we apply: Image Tracking Correlation of scans pmode Filter Masks Segmentation Algorithms Granular mask: A variable threshold in a box of 1.8' ' square locates granules => “locally high mountains” Intergranular mask: Skeleton, that finds midpoints between granules, enlarges these lines with darker points, again finds midpoints... (Berrilli,1998) => “valleys between mountains” Turbulence FWHM of 7090.4 Å line granules and intergranules are clearly distinguished => masks do good job slightly bigger FWHM in intergranules => higher turbulence in intergranules, as they are even colder than granules (confirms e.g. Puschmann 2003) Turbulence Unfiltered and Pmode filtered FWHMs => influence of oscillations? Bisectors Bisector Velocities Seperated for Granules and Intergranules Filtered for 5min oscillations => Same kind of shape for granular and intergranular bisectors. (unlike Hanslmeier 2000) Slightly straighter bisector over intergranules. (like Maltagliati 2000) Still, small patches of bisectors show a broad variety of shapes. Future Outlook: First polarimeter tests with IBIS in October 2004 Investigation of turbulence at granule borders Tracking of bisectors from center to border of granules Comparison of line parameters with simulations Thanks for listening! Katja Janßen is a member of the European Solar Magnetism Network (ESMN) supported by the EC through the RTN programme. Unfiltered Bisectors Bisector Velocities Granules and Intergranules Not Filtered for 5min oscillations Cores Core Velocity in 7090.4 Å line Filtered for pmodes
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