Abstract
Photoelectric polarisation measurements in a stable sunspot (type H) with a particularly dark umbra carried out with the Capri magnetograph have been evaluated in terms of Unno's (1956) theory to give the value and direction of the magnetic field vector. A linear increase of the inclination angle with distance from the spot centre up tor ≈ 1.2R s results, as originally found by Hale and Nicholson (1938) with a different procedure. The field strength decreases from the maximum value (about 3300Γ) to about 15% at the penumbral border, still continuously decreasing outside the spot. The projected field direction deviates considerably from the radial symmetry in several parts of the spot region, but it is in good agreement with that of the overlaying chromospheric structures.
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Mitteilungen aus dem Fraunhofer Institut Nr. 97.
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Deubner, F.L., Göhring, R. Photoelectric polarimetry of a dark unipolar sunspot. Sol Phys 13, 118–125 (1970). https://doi.org/10.1007/BF00963946
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DOI: https://doi.org/10.1007/BF00963946