Long-term variations in the sunspot magnetic fields and bipole properties from 1918 to 2014

Long-term measurements of sunspot magnetic fields have been analyzed with the use of the Mount Wilson Observatory (MWO) data based on the digitization of the magnetic field strength (B) and umbra and pore areas from 1918 to 2014. Time variations in the magnetic field strength and the possible causes of such variations (which are related to variations in the solar activity level and instrumental effects) were considered. It was shown that artifacts related to instrumental effects exist in the measurements for small sunspots and pores. The magnetic bipole characteristics were determined for the sunspot groups. It was established that the tilt angle of the magnetic bipole axis of even cycles is larger than the tilt angle in the next odd cycles (except for the cycle pair 22–23).