Solar Flare Observations at the Crimean Astrophysical Observatory (Ukraine)

Abstract

Spectropolarimetric observations and measurements at the Crimean Astrophysical Observatory (Ukraine) resulted from traditional Zeeman spectropolarimetry employed to measure the local magnetic field strength. By studying the magnetic field from polarization spectrograms in an H_α line obtained with a circular polarization analyzer in the mid-1970s, Koval⁽²²⁶⁾ identified structural elements of different polarity in some flare knots. It would be logical to attribute this difference to the magnetic field. At the same time, these polarization data may well be distorted by other effects, such as the presence of linearly polarized emission caused by resonance scattering, the turbulent Stark effect, and anisotropic excitation of atoms by accelerated beams. This aspect of solar flare emission was quite poorly studied at that time. Therefore, the Crimean group during the 1970s and 1980s undertook systematic and careful observations of linear polarization in solar flare emissions.