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Left: the axial magnetic “dipole moment” of the Sun, defined as the difference between the (signed) magnetic field strength near the North Pole and near the South Pole, for the past four solar cycles. To facilitate comparison of cycles, a “ghost” mirror image is also plotted. Data from Mount Wilson Observatory (blue) has been scaled to match observations from Wilcox Solar Observatory (red). Right: the polar field variation at the left scaled by the maximum smoothed sunspot number for the next cycle suggesting the same variation for each cycle, i.e., that the cycle maximum is controlled by the polar fields at the preceding minimum. For Cycle 24, the maximum was not known, but a very high value (165) or a very low value (45) does not fit the pattern. A maximum size of 72 for Cycle 24 seems to be the just right “Goldilocks” value.
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