Bulletin of Taras Shevchenko National University of Kyiv. Astronomy, no. 59, p. 12-16 (2019)
SIGNIFICANT INHOMOGENEITY OF A MAGNETIC FIELD IN THE GREATEST SUNSPOT OF ACTIVE REGION NOAA 10488
V. Lozitsky, DrSci
Astronomical Observatory of Taras Shevchenko National University of Kyiv
Abstract
The main conclusion of our work is that in the greatest sunspot of the active region NOAA 10488 there was a large dispersion of magnetic field strengths, at which the minimum and maximum strengths differed by approximately an order of magnitude. This result applies to the central part of the sunspot umbra, for a square with sides 2 × 2 Mm2 in the picture plane. Observation material was obtained on the Echelle spectrograph of the horizontal solar telescope of the Astronomical Observatory of Taras Shevchenko National University of Kyiv. This instrument allows to analyze the Zeeman effect simultaneously in thousands of spectral lines of almost the entire visible region of the spectrum. For our analysis, four iron FeI lines with wavelengths of 6290.97, 6301.51, 6302.50 and 6498.97 Ǻ and effective Lande factors 1.481, 1.669, 2.487 and 1.375, respectively, were used. In the studied sunspot, only FeI 6302.5 from these lines has a complete Zeeman splitting, which corresponds to magnetic field of 3400 G. However, the splitting of the other three lines corresponds to magnetic fields in a very wide range, from several hundred Gauss to 3700 G, which indicates significant inhomogeneity of the magnetic field. Also, the shape of bisectors of I ± V profiles does not correspond to a case of homogeneous field. In particular, theoretically, in a homogeneous and non-longitudinal magnetic field, bisectors should be have the maximum splitting in the nuclei of these lines, whereas in reality the picture is more complicated. All three of these lines show a tendency to increase splitting in distant wings, at distances of 120-250 mAh from their centers. This effect is possible under the two-component structure of the magnetic field (background field + spatially unresolved structures) having magnetic strengths in the range of 4.5-8 kGs in spatially unresolved structures. Magnetic polarity in both components is the same, namely N. The observational data indicate that the magnetic field value differed significantly not only on the surface, but also in height in the studied sunspot.
Key words
Sun, sunspots, magnetic fields, active region NOAA 10488, Echelle Zeeman-spectrographs, bisectors of profiles of spectral lines, spatially unresolved structures, magnetic field inhomogeneity
References
Botygina, O.O., Gordovskyy, M.Yu., Lozitsky, V.G. 2016, Advances in Astronomy and Space Physics, 6, 20
Domínguez Cerdeña, I., Sánchez Almeida, J., Kneer, F. 2003, Astronomy and Astrophysics, 407, 741
Gordovskyy, M., Lozitsky, V.G. 2014, Solar Physics, 289, 10, 3681
Livingston, W., Harvey, J.W., Malanushenko O.V. 2006, Solar Phys., 239, 41
Lozitska, N.I., Lozitsky, V.G, Andryeyeva, O.A. 2015, Advances in Space Research, 55, 3, 897
Lozitsky, V.G. 2015, Advances in Space Research, 55, 3, 958
Lozitsky, V.G. 2016, Advances in Space Research, 57, 398
Lozitsky, V. G., Yurchyshyn, V. B., Ahn, K., Wang, H., Lozitska, N. I. 2018, Odessa Astronomical Publications, 30, 152
Moore, C.E., 1945, 20, Princeton, New Jersey, 96
Rachkovsky, D.N., Tsap, T.T., Lozitsky, V.G. 2005, Journal of Astrophysics and Astronomy, 26, 435
Stenflo, J.O. 1973, Solar Physics, 32, 1, 41
Steshenko, N.V. 1967, Bull. Crimea. Astrophys. Obs., 37, 21
Takenori J. Okamoto, Takashi Sakurai. 2018, The Astrophysical Journal Letters, 852, 1, id. L16, 6
Van Noort, M., Lagg, A., Tiwari, S.K., Solanki, S.K. 2013, Astron. Astrophys., 557, id.A24, 14
Wang, Y., Yurchyshyn, V., Lin, C., 2018, Res. Notes of the American Astron. Society, 2, 1, id. 8
Wiehr, E. 1978, Astron. and Astrophys, 69, 2, 279
Zemanek, E.N., Stefanov, A.P., 1976, Vestnik Kiev University, Seria Astronomii, 18, 20