Threshold of a mini-Maunder

Much has been made of the probable connection between the Maunder Minimum, a 70-year deficit of sunspots in the late 17^th-early 18th century, and the coldest part of the Little Ice Age, during which Europe and North America were subjected to bitterly cold winters.  The mechanism for that regional cooling could have been a drop in the sun’s EUV output; this is, however, speculative.

The yearly averaged sunspot number for a period of 400 years (1610-2010). SOURCE: Courtesy of NASA Marshall Space Flight Center.

The sun could be on the threshold of a mini-Maunder event right now.  Ongoing Solar Cycle 24 is the weakest in more than 50 years.  Moreover, there is (controversial) evidence of a long-term weakening trend in the magnetic field strength of sunspots. Matt Penn and William Livingston of the National Solar Observatory predict that by the time Solar Cycle 25 arrives, magnetic fields on the sun will be so weak that few if any sunspots will be formed. Independent lines of research involving helioseismology and surface polar fields tend to support their conclusion.

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