EARTH
CREDIT/Kathleen Cantner, AGI
Sometime in the next few months — summer or fall of 2013, according to NASA’s Marshall Space Flight Center — the sun will reach the solar maximum, the peak of sunspot counts during its roughly 11-year cycle. Despite the sun’s seeming regularity, each solar cycle remains to some extent unpredictable. Although the average cycle lasts about 11 years, some are as long as 14 years or as brief as nine. Solar storms might be mild during a solar maximum or severe during a minimum.
As solar science continues to advance, researchers are finding new ways to study and forecast the behavior of our star, whose whims endanger our technology-dependent way of life. But what the upcoming peak means for solar storms, and how those storms will affect Earth, remain to be seen.
The Unruly Dynamo
The sun’s cycle is marked from minimum to minimum, so the solar maximum occurs about halfway through the cycle. Scientists are not certain why the cycles consistently last about 11 years, but they do understand the mechanisms that cause solar activity like solar flares and coronal mass ejections (CMEs).
The sun’s magnetic field, like Earth’s, is generated from within by the flowing motion of material. But while Earth’s magnetic field is perpetuated by the churning of molten metal in the planet’s liquid outer core, the sun’s magnetic field is produced by the movement of plasma — a superheated state of matter in which electrons have been stripped from atoms, leaving a gas-like body of positive ions and free electrons.
Neither Earth’s nor the sun’s magnetic field is symmetric, stable or stationary. But the sun’s magnetic fields are more complex than Earth’s. Rather than one north and one south pole, the sun has many poles, with magnetic fields that constantly swell, bend and twist. A map of the sun’s magnetic structure at any given moment appears more like a tangled ball of yarn or a bunch of writhing snakes than the symmetrical toroid of textbook illustrations, and over an 11-year cycle, the sun’s whole magnetic structure flips. And it is that writhing and tangling that produces the solar activity that affects the rest of the solar system.
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