Journal of Physical Studies 23(4), Article 4903 [7 pages] (2019)
DOI: https://doi.org/10.30970/jps.23.4903

MIXED-POLARITY MAGNETIC FIELDS IN THE AREA OF A SEISMIC SOURCE ASSOCIATED WITH A LARGE PROTON SOLAR FLARE

V. G. Lozitsky1, E. A. Baranovsky2, N. I. Lozitska1, V. P. Tarashchuk2

1Astronomical Observatory of the Taras Shevchenko National University of Kyiv, Kyiv, Ukraine,
2Crimea Astrophysical Observatory, Nauchny, Crimea
e-mail: lozitsky_v@ukr.net

We found observational evidence of a close contact of strong magnetic fields with opposite magnetic polarities in the area of a seismic source connected with the large proton solar flare of October 28, 2003 of X17.2/4B class. The observations were carried out with the Echelle spectrograph of the Astronomical Observatory of Taras Shevchenko National University of Kyiv. Our analysis is based on the observations of $I\pm V$ profiles of nine spectral FeI lines with different Lande factors and height of formation in the atmosphere. Probably, the magnetic field structure in the flare contained at least two components, namely, the moderate background field of S polarity and spatially unresolved fluxtubes with strong magnetic fields ($\sim 10^3$\,G). At the level of the middle photosphere ($h\simeq 300$ km), the magnetic field polarity in fluxtubes was likely N, that is, opposite to the polarity of the background field. This is indicated by the fact that the photospheric lines with the Lande factors in the range $q_{\rm eff} = 1.0\div1.5$ showed smaller measured magnetic fields $B_{\rm eff}$ than the lines with $q_{\rm eff} = 2.0\div3.0$. In contrast, in the upper photosphere and in the temperature minimum zone, the magnetic polarity in the strong component was S, which follows from the splitting of emission peaks in the Fe I 5269.5 and Fe I 5397.1 lines. This picture was observed on an area of approximately 2.5 Mm$^2$, which corresponds to the spatial resolution of our observations. The semi-empirical model, constructed on the basis of the observations of Fe I 5123.7 and 5434.5 lines, has a unique peculiarity, namely, a very thin layer (40-50 km) in the upper photosphere where the magnetic field reaches 90 kG and has N polarity. Perhaps, such a very heterogeneous magnetic field structure on the photospheric level (sign-changing with height) caused the necessary conditions for the appearance of a seismic source in the solar flare.

PACS number(s): 96.60.Hv, 96.60.Q-, 96.60.qe

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