Аннотация:The results of the study of the star formation region G 109.871+2.114 (Cep A) in OH lines at 18 cmare presented. Polarization observations (monitoring) were performed with a large Nançay radio telescope(France) in 2007–2024. OH maser emission is highly variable. The structure of the spectrum and the fluxdensity of the individual spectral features are changing. However, the radial velocities of most featureschanged slightly. Short-term emission flares in individual features were observed. Many features have strongcircular polarization, reaching 100%, but have weak linear polarization. A new features at –15.53 km/s and ashort-term part at 1.58 km/s with high circular and low linear polarizations were detected in the 1667 MHzline. The spectral features of our monitoring were spatially identified with the maser spots on the Cohen,Argon, and Fish maps. The magnitude of the monotonic decrease in splitting, and, consequently, the longitudinalmagnetic field of three Zeeman pairs (–16.2L/–14.25R and –6.94L/–0.82R km/s in the 1665 MHzline and –15.76L/–14.2R in the 1667 MHz line). For the –13.95L/–11.60R pair, no splitting change wasdetected in the 1665 MHz line. Broadband absorption and emission are observed in the satellite lines of1612 and 1720 MHz, respectively. A Zeeman pair was also detected in the 1720 MHz line. The position angleis calculated for linearly polarized emission of most spectral features in both main lines at 1665 and1667MHz. It is shown that the magnetic field in the H II regions is oriented either along the external magneticfield or along the radio jets.
