Abstract
During our spectropolarimetric observations of the 2B/4.8X flare on July 23, 2002, with the Large Solar Vacuum Telescope (LSVT), we detected impact linear polarization in the southern ribbon. The maximum polarization exceeded 10%. On the whole, the polarization was observed only for ~6 min out of almost 2 h of observations of this flare. At this time, the Hα line profiles had a deep central self-reversal. We have compared the LSVT observations with the Reuven Ramaty High Energy Solar Spectroscopic Imager (RHESSI) data, where the locations of γ-ray emission were obtained for the first time. A careful comparison has revealed that the effects in the Hα line were observed in a region <10″ located between two X-ray sources in the southern ribbon. According to the RHESSI data, a γ-ray source attributable to a beam of high-energy (~1 MeV) electrons was observed at the same place. The events in the corona and the upper chromosphere also coincide in time with the observed effects in the Hα line. The two X-ray sources are assumed to represent a common footpoint of the southern foot of the loop bifurcated due to the precipitation of high-energy electrons. It is suggested that the penetration of these electrons into the dense layers of the chromosphere could lead to impact polarization and a decrease of the Hα line intensity in the southern ribbon of the flare, in contrast to the northern ribbon where a typical hard X-ray source with an energy ~20–120 keV was observed; there were no self-reversal at the Hα line center and polarization.
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Original Russian Text © N.M. Firstova, 2015, published in Pis’ma v Astronomicheskiĭ Zhurnal, 2015, Vol. 41, No. 10, pp. 642–650.
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Firstova, N.M. Connection between the appearance of γ-ray sources and Hα line impact linear polarization in the July 23, 2002 flare. Astron. Lett. 41, 593–600 (2015). https://doi.org/10.1134/S1063773715090029
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DOI: https://doi.org/10.1134/S1063773715090029