Preprocessing of Hinode/SOT vector magnetograms for nonlinear force-free coronal magnetic field modelling
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The solar magnetic field is key to understanding the physical processes in the solar atmosphere.
Nonlinear force-free codes have been shown to be useful in extrapolating the coronal field from underlying vector boundary data [see Schrijver et al. 2006 for an overview]. However, we can only measure the magnetic field vector routinely with high accuracy in the photosphere with, e.g., Hinode/SOT, and unfortunately these data do not fulfill the force-free consistency condition as defined by Aly (1989). We must therefore apply some transformations to these data before nonlinear force-free extrapolation codes can be legitimately applied. To this end, we have developed a minimization procedure that uses the measured photospheric field vectors as input to approximate a more chromospheric like field The method was dubbed preprocessing. See Wiegelmann et al. 2006 for details]. The procedure includes force-free consistency integrals and spatial smoothing. The method has been intensively tested with model active regions [see Metcalf et al. 2008] and been applied to several ground based vector magnetogram data before. Here we apply the preprocessing program to photospheric magnetic field measurements with the Hinode/SOT instrument.
2 pages, 1 figure, ASP Conference Series, Hinode Science Meeting, Dublin, 20-24th August 2007
2 pages, 1 figure, ASP Conference Series, Hinode Science Meeting, Dublin, 20-24th August 2007