Nonaxisymmetric Component of the Solar Photospheric Magnetic Field

Abstract

The longitudinal asymmetry of the photospheric magnetic field distribution is studied based on data from the Kitt Peak National Solar Observatory (synoptic maps for 1976–2016). Vector summation is used to weaken the effect of a stochastic component uniformly distributed along the longitude and to emphasize the stable nonaxisymmetric field component. Distributions of magnetic fields with different strength are considered: strong (B > 50 G), weak (B < 5 G), and medium (50 > B > 5 G). It is shown that the longitudinal asymmetry in all the groups of fields varies in phase with the 11-year solar cycle. The asymmetry of the strong and medium fields varies in phase with the magnetic fluxes of these fields, whereas that of weak fields is in antiphase with the flux of the weak fields. The longitudinal distributions of the strong and medium magnetic fields resemble each other in shape: the distribution maximum is located at a longitude of ~180° during the ascent–maximum period of the solar cycle and at a longitude of ~0°/360° during the decrease–minimum period. Weak fields show the opposite picture: their distribution maximum is always located at the longitude of the strong and medium field minimum.