EVIDENCES FOR STRONG MIXED-POLARITY MAGNETIC FIELDS IN AREA OF A SEISMIC SOURCE ASSOCIATED WITH LARGE PROTON SOLAR FLARE
We present in a concise statement the new
results based on spectral-polarization measurements of
magnetic fields in an extremely powerful proton solar
flare on October 28, 2003 of X17.2 / 4B class. The
observation material was obtained with Echelle
spectrograph of HST AO KNU, which makes it possible
to analyze the spectral manifestations of the Zeeman
effect in very many lines of the visible region of the
spectrum, including the photospheric and chromospheric
lines. The I ± V and V profiles of about ten FeI and FeII
lines, as well as the Hα, Hβ, Hγ, and Hδ lines were studied
in a area of the seismic source of the flare, which was
localized in the sunspot penumbra of S magnetic polarity.
In this flare, we found an unprecedented Balmer
decrement of intensities of Hα and Hβ lines which
corresponds to ratio I (Hβ) / I (Hα) = 1.68. In the FeI
5434.5 line with very low Lande factor (g eff = –0.014), a
reliable splitting of emission peaks was found, which
could indicate superstrong magnetic fields (about 50 kG)
of N polarity. Indications for magnetic fields with
intensity ≈ 12 kG of S polarity were found too. These
indications are based on the study of the Stokes V profile
of FeII 5234.6 line. In this line, there were two positive
and two negative peaks of profile V, indicating a two-
component structure of the magnetic field. According to
the simulation data, the small-scale component with the
above-mentioned superstrong magnetic field had a filling
factor about 0.1 and had narrow (about twice) the half-
widths of the line profiles. The close contact of
subtelescopic magnetic fields of different magnetic
polarity, but of lower intensity (B ≈ 1 kG) was also
indicated by the comparison of the half-widths of the FeI
5247.1 and 5250.2 lines. In general, it can be concluded
that the necessary conditions for the reconnection of
magnetic lines were fulfilled even at the photospheric
level, rather than in the corona or chromosphere, as
suggested by theoretical models of solar flares.
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