Astronomy and Astrophysics – Astrophysics
Scientific paper
Jul 1992
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1992a%26a...261..321k&link_type=abstract
Astronomy and Astrophysics (ISSN 0004-6361), vol. 261, no. 1, p. 321-328.
Astronomy and Astrophysics
Astrophysics
77
Astronomical Polarimetry, Solar Activity, Solar Atmosphere, Speckle Interferometry, Power Spectra, Telescopes, Transfer Functions, Zeeman Effect
Scientific paper
The combination of a polarimeter with real-time frame selection and differential speckle imaging results in diffraction-limited magnetograms that provide new insight into the morphology of solar small-scale magnetic fields. The method to record diffraction limited narrow-band filtergrams of solar features is based on two cameras taking simultaneous short exposure images through a broad-band and a narrow-band filter, respectively. Speckle imaging reconstructs the image in the broad-band channel. This reconstruction determines the instantaneous optical transfer function (OTF) for each individual broad-band exposure. Each simultaneously recorded image in the narrow-band channel is then corrected for the instantaneous OTE To recover all spatial frequencies in the narrow-band channel the so corrected single images are averaged. We have applied the method to polarimetric observations of a solar active region by tuning the narrow-band filter to the wing of a Zeeman sensitive spectral line. The most active part of the region shows no more normal granules but features with a diameter of 0.3 to 0.5 arcsec. The smallest magnetic fields are concentrated in regions with sizes at or below the diffraction limit of the telescope.
Keller Christoph U.
von der Luehe Oskar
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