The crossover and magneto-optical effects in sunspot spectra

Abstract

Two peculiarities of the magnetic splitting of lines in sunspot spectra have been investigated. The first one consists of the fact that in a rather small region of the penumbra, near the umbrapenumbra boundary, the π-component is absent in the spectra of one circular polarization while both σ-components are present. In the spectra of the opposite circular polarization, the σ-components are absent but the π-component is present. By analogy with the magnetic stars, in whose spectra such an effect was observed by Babcock, this phenomenon was called by us the ‘crossover effect’ in the sunspot spectra. Some properties of this effect in the different spectral lines were investigated. The nature of this effect is discussed. The second peculiarity consists of the anomalous splitting of the π-component of Zeeman triplets which are of the same and opposite signs in comparison with splitting of the σ-components. The different possibilities of explanation are discussed.