Nonaxisymmetric Component of the Solar Photospheric Magnetic Field

Abstract

The longitudinal asymmetry of the photospheric magnetic field distribution is studied on the basis of the data of the Kitt Peak National Solar Observatory (synoptic maps for the period 1976-2016). The method of vector summing of magnetic fields is used, which allows to decrease the influence of the stochastic components uniformly distributed over the whole longitude interval, and to stress a steady non-axisymmetric component of the field. The distributions of magnetic fields of different intensity are considered separately for the strong (B > 50 G), weak (B < 5 G) and medium (50 > B > 5 G) fields. It is shown that the longitudinal asymmetry for all groups of fields changes in phase with the 11-year cycle of solar activity. The asymmetry of strong and medium fields changes in phase with magnetic fluxes of these fields, while the asymmetry of weak fields is in antiphase with the flux of weak fields. The distributions of strong and medium magnetic fields over the longitude are similar in the shape: The maximum of distribution is located at the longitude ∼ 180 • during the period of ascent-maximum of solar cycle and at the longitude ∼ 0 • /360 • during the period of descent-minimum. The weak fields exhibit the opposite picture: the maximum of their distribution is always observed at the longitude, where the strong and medium fields show minimum.