The development of the solar polar field strength throughout a solar sunspot cycle can be used to predict the magnitude of the next cycle and the peak of the current cycle. Polar field reversals typically occur within a year of sunspot maximum. It is not uncommon for the northern and southern polar fields to have significant differences in field strength and develop asynchronously over time.
The northern polar field reversed in June 2012 while the southern polar field reversed in July 2013. During the previous similar polarity reversal in 1989-1991 the northern polar field reversed 14 months prior to the southern polar field reversal, very similar to the situation during cycle 24.
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