Polar and Large-scale Magnetic Field Patterns in Solar Cycles 25 and Before

Solar Cycle 24 got off to a very slow start after an extended minimum that ended in late 2008, and activity was highly asymmetric in both phase and intensity between the northern and southern hemispheres. This was reflected in the slow reversal of the polar field around maximum, the asymmetric development of the new polar field in the declining phase, and the relatively early decay of the polar field strength that began before the recent minimum between Cycles 24 and 25 at the end of 2019. At the same time, the large-scale patterns of the solar magnetic field at lower latitudes were quite strong in Cycle 24, with the mean magnetic field of the Sun observed as a star from the Earth in the ecliptic reaching a 20-year high in October 2014 at more than 2 G. Because the cycle was relatively weak, the influence of a small number of individual active regions was important to the development of these large-scale patterns. Consistent long-term observations from the Wilcox Solar Observatory since 1976 are compared with other measurements of the large-scale photospheric field patterns to compare features of the last four activity cycles.