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The Sun Has Seasons

And you thought it was just “hot”

(Corbis)
smithsonian.com

Yes, this is a metaphor—the sun doesn't experience a terrible snowy winter and then mere weeks later descend into a humid, sticky mess. But the sun does have weather, in the form of fluctuating magnetic fields. And, it turns out, there's seasonal variability in that weather, scientists at the National Center for Atmospheric Research announced this week.

Our star has an 11-year cycle, in which the hot soup of particles flowing within vary the magnetic field on the star's surface. That variability shows up in sunspots—regions that are thousands of degrees cooler and 1,500 to 30,000 miles wide—and can shoot streams of charged particles at us at millions of miles per hour. These solar storms cause auroras, and sometimes even blackouts. At the peak of the cycle, sunspots are common.

But solar flares and other ejection of gas and force often peak just after the sun the reaches its peak sun-spotty-ness. And, researchers say, a pattern of two-year variability might explain that lag.

The pattern, they think, is caused by changes in magnetic field bands in the star's northern and southern hemispheres. It's as though the sun has a dry season and a wet season, lead author Scott McIntosh explains in a statement. Except instead of rain, the sun has bursts of gas and particles, with energies totaling that of hundreds of millions of tons of TNT.

About Shannon Palus

Shannon Palus is a science writer, and a researcher for Popular Science. Her work has appeared in Discover, Slate, Ars Technica, and elsewhere. She is based in Philadelphia.

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