“The sun has a heartbeat of about 11 years,” Spangler said. “It’s like a human heartbeat. There’s variation to it.”
Such variations in activity have been observed in other sun-like stars. Spangler said it appears to be “a basic property of middle-aged stars.”
Solar weather, which can produce flares and massive explosions called coronal mass ejections, tends to pick up at the peak of the 11-year cycle. But that’s not happening right now. We’re at or near the peak, and there’s just not much going on.
Sunspot activity during the last solar maximum was measured at approximately double the current activity. And the most recent solar minimum was even wimpier.
“The present maximum is low. The previous minimum was really low,” said Spangler.
But something else is happening, too. There appears to be a multi-decadal cycle in the sun’s activity. In 1958, the solar maximum was about three-and-a-half times as busy as it is now. The maximums have declined since.
Why? Spangler said there really isn’t a good answer.
“We don’t know what causes that.”
The lack of activity has led to some speculation that this could mirror the start of the Maunder Minimum, a period of extraordinarily low solar activity. If the 11-year cycle is a mood swing from a middle-aged star, the Maunder Minimum was a full-blown midlife crisis.
The minimum had profound effects on the Earth, where temperatures dropped enough to give the period the nickname, “The Little Ice Age.” But speculation that solar activity could be leading into a similar lull is just that right now: speculation.
Spangler puts little faith in it. Predicting solar activity is tricky. The best models from 2006 predicted an unusually active solar maximum, a prediction we now know was way off the mark.