‘Rogue’ Sunspots Spoil Chances for Long-Term Space Weather Forecasting:

The number of solar spots and eruptive phenomena connected to them show cyclical variations with a mean period of 11 years. The strength of these solar cycles, however, varies considerably. We know about periods in the past, called Grand Minima, when no sunspots were observable for decades. This was also the case during the Maunder Minimum in the second half of the 17th century, which thought to be associated with the “Little Ice Age.” On the other hand, we observed a period of very strong cycles, known as Modern Maximum at the end of the last century. The currently-ongoing Cycle 24 is breaking this series with an amplitude much lower than the typical values during Modern Maximum. Forecasting these long-term, cycle-to-cycle variations is the Holy Grail of solar dynamo theory, the discipline studying the origin of solar activity. In recent years, our understanding of the driving mechanisms of the solar dynamo has developed significantly, however, sadly, the new results also pointed out the limits of predicting the properties of the upcoming solar cycle.

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