Variations in the Magnetic Field Strength of Pre-main-sequence Stars, Solar-type Main-sequence Stars, and the Sun

Abstract The surface magnetic fields of pre-main-sequence stars and zero-age main-sequence stars are notably strong, resulting in the generation of numerous spots and the emission of bright chromospheric lines. Rotational variations in magnetic field strength have been identified in T Tauri stars (TTSs) and young main-sequence stars using Zeeman–Doppler imaging. This study investigates the relationship between the mean values and variation amplitudes of the magnetic field strengths of TTSs, main-sequence stars, and the Sun. The findings reveal a positive correlation of over 3 orders of magnitude, suggesting that a common mechanism drives the magnetic fields of these stars. This positive correlation implies that stars with larger spot sizes experience greater variation amplitudes due to rotational modulations. For the Sun, both the mean magnetic field strength value and its variation amplitude tend to be higher during solar maximum than during solar minimum.