Unique spectral manifestations around the D3 line observed in the region close to the seismic source of a large solar flare

Abstract

ABSTRACT The main goal of our research is to search for super-strong magnetic fields in active processes on the Sun. Our method is based on Stokes V spectro-polarimetry in a wide spectral range from −14 Å to +29 Å relative to the D3 He i line. The object of the study is the area of a seismic source in the large solar flare on 2003 October 28 of the X17.2/4B class. The novelty of our study: we found characteristic spectral manifestations – secondary Stokes V peaks – far from D3 line, at distances of several angstroms. These secondary peaks have the following features: (a) their amplitudes reach 4 per cent – almost an order of magnitude more than previously detected in other flares, (b) in the general picture, the sign of the circular polarization changes when passing through the D3 centre, and (c) narrower spectral peculiarities were found at distances of +4.0, +6.3, and +8.5 Å, where the polarization sign also changes sharply. This unusual feature likely results from significant factors in the area of the seismic source, including substantial descending plasma velocities which exceed 400 km s−1 and, perhaps, super-strong magnetic fields.