Bulletin of Taras Shevchenko National University of Kyiv. Astronomy, no. 58, p. 23-28 (2018)

Measurements of spatially unresolved magnetic fields of mixed polarity using observations of the Zeeman effect in the solar faculae

V. Lozitsky, Dr. Sci.

Astronomical Observatory of Taras Shevchenko National University of Kyiv, Kyiv


It is shown that it is quite possible to measure spatially unresolved magnetic fields of mixed polarity by the Zeeman effect if their intensity exceeds 150-200 G. This means that one can interconnect the ranges of the registration of these fields based on the Hanle and Zeeman effects. This thesis is illustrated by the results of calculations of the half-width of the Stokes profile I for the FeI 5247.1 and 5250.2 lines. Parameter I is sensitive to the presence of magnetic fields, regardless of whether they have the same magnetic polarity within the input aperture of the instrument, or the opposite one. According to the calculations, if the accuracy of the measurement of the half-width ratio of these two lines is increased to 0.5 %, then it is possible to measure the magnetic fields from 70-100 G. On the basis of the proposed method, an estimate of the intensity of the magnetic fields of mixed polarity in a solar faculae in the tail part of the active region NOAA 1809 was made, which on the day of observations, August 6, 2013, was located not far from the Sun’s disc center. The Echelle Zeeman-spectrogram of this region was obtained on the Horizontal Solar Telescope of Astronomical Observatory of Taras Shevchenko National University of Kyiv. The magnetic field in the faculae was measured in two ways: by shift of of the “center of gravity”of the profiles of the FeI 5247.1 and FeI 5250.2 Ǻ lines in the I + V i I – V spectra and also by the half-width ratio of the profiles I of these lines. The first method allows to measure the effective magnetic field Beff, which turned out to be 280 G by FeI 5250.2 and 360 G by FeI 5247.1. The corresponding ratio Beff (5247.1) / Beff (5250.2) ≈ 1.3 indicates the existence of the sub-telescopic flux tubes with kilogauss fields. However, the ratio of the half-width of the Stokes I profiles of these two lines is 1.08, which corresponds to the magnetic field ± 650 G, if magnetic field is purely longitudinal. Based on the analysis of these data as well as the results of other studies, one can conclude that in the investigated faculae there were probably three magnetic field field components: the fluxtubes with kG field Bfluxtube, the areas of background field Bbackgr of regular magnetic polarity, and the areas of subtelescopic fields Bmixpol of mixed magnetic polarity. In absolute value the magnetic flux of tangled mixed-polarity field exceeds the flux of entire regular field with the intensities of Bfluxtube and Bbackgr at least 2-fold.

Key words
Sun, solar magnetic fields, solar faculae, Echelle Zeeman spectrograms, spatially unresolved magnetic fields of mixed polarity, three-component structure of magnetic fields

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DOI: https://doi.org/10.17721/BTSNUA.2018.58.23-28