Possible Signatures of Extremely Strong Magnetic Fields Observed in a Sunspot Based on Spectropolarimetry near the D3 Line

Abstract

The main goal of the study is to search for super-strong magnetic fields in “quiet” sunspots without flares. The authors’ method is based on Stokes V spectropolarimetry in a wide spectral range, from –5 to +2.5 nm relative to the D₃ He I line. The objects of the study are two simple sunspots with diameters of 35–40 Mm, observed on 17 and 24 July, 2023, near the center of the solar disk, at heliocentric angles of approximately 18°. Novelty of the study consists in the fact that characteristic spectral features are detected in the second sunspot at distances of approximately –1.88 and –0.84 nm from the D₃ He I line, which can be strongly split sigma-components in the Zeeman effect of the mentioned line for the following principal reasons: (a) their Stokes V signs are opposite, and the amplitudes reach 5%, which significantly exceeds the measurement errors, (b) the amplitudes of the blue and red peaks vary synchronously in different places of the sunspot, and (c) the spectral profiles of both peaks have similar shapes and are mutually antisymmetric. If the indicated spectral features are interpreted as a manifestation of the combined action of the Zeeman and Doppler effects, then one can assume the presence of very fine-structured (spatially unresolved) jets in the sunspot that have a magnetic field on the order of 10⁵ G and a plasma ascent speed at the level of 700 km/s. Within this interpretation, it becomes possible to address two current problems in heliophysics: the anomalously rapid rotation of the corona at low latitudes and the occurrence of super-strong magnetic fields at chromospheric and coronal levels.