Astronomy and Astrophysics – Astronomy
Scientific paper
Aug 2006
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2006iaujd...3e..22l&link_type=abstract
Solar Active Regions and 3D Magnetic Structure, 26th meeting of the IAU, Joint Discussion 3, 16-17 August, 2006, Prague, Czech R
Astronomy and Astrophysics
Astronomy
Scientific paper
We study small-scale (spatially unresolved) magnetic field structure in some solar flares of current 23th solar activity cycle, including X class flares, e.g. X17.2/4B flare of October 28, 2003 and X1.7/1B flare of March 29, 2001. Our spectral data were obtained with the Echelle spectrograph of the horizontal solar telescope of the Astronomical Observatory of Kyiv Shevchenko National University. For small-scale magnetic field diagnostics, the Stokes I ± V profiles were compared for different spectral lines including FeI, FeII, HI, D [3]HeI, D[1] and D[2] NaI. For all the most bright flare knots we had found certain differences between magnetic field values measured in FeI 6301.5 and 6302.5 Å lines using the `center of gravity' method. The corresponding line ratio, in general, is here T[eff](6302.5)/T[eff](6301.5) > 1, contrary to ordinary ratio T[eff] (6302.5) / T[eff] (6301.5) < 1 measured at non-spot and non-flare regions. Detailed study of Stokes V profiles shows that named effect was caused likely by a very strong subtelescopic magnetic field of mixed polarity. Corresponding small-scale structures could not be in a form of any long fluxtubes, but more probable - small-scale quasi-spherical magnetic tangles or vortexes. The magnetic field amplitudes reach here at least 5-6 kG. Although the most strong fields were observed in upper photosphere and temperature minimum zone, the fields of kG range were detected in the chromosphere too. Perhaps, narrow mixed-polarity structure and kG range of magnetic field amplitude present the necessary conditions for magnetic reconnection process in flares.
Lozitska N. I.
Lozitsky V. G.
Lozitsky V. V.
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