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On 2002 July 23, a major 2B/X4.8-class flare was observed in Ha lines with the Large Solar Vacuum Telescope of the Baikal Astrophysical Observatory using the spectropolarimetric method. Linear polarization of 3%-10% has been detected in Ha lines of the flare, particularly in the Ha lines with a central reversal. They are mainly radial on the solar disk and appear at the impulsive phase of hard X-ray and g-ray bursts. The polarization changes its direction in a spatially limited small region (∼4Љ-5Љ) and within a short period of time (∼10 s). Moreover, the linear polarization is limited to only some relatively small regions of the flare.

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A study has been made of linear polarization in 'moustaches' using the He and Hfl lines. A Wollaston prism and an achromatic 2/2-plate were employed in the study. In the course of the observations, the major axis of the plate was placed at 0 ~ and 22?5 with respect to the horizontal axis of the installation. The Stokes parameters J, Q, and U were recorded, thus enabling the degree of polarization and the field azimuth to be determined. During the first three minutes of the existence of the moustaches, the two lines revealed a linear polarization of about 7~o located at the center of the lines. No polarization was found during the later stage of the moustaches' lifetimes. Whenever the linear polarization is present, there is a tendency for the polarization to decrease rapidly, in accompaniment of a turning of the azimuth. Several mechanisms for interpreting the polarization observed in the moustaches are examined. Some suggestions are made in support of the excitation of hydrogen atoms in the moustaches initiated by a high-energy electron flux or vertical heat conduction.

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