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Unpredictable Sun

April 29, 2015

The Sun is unpredictable — just ask the scientists who try to predict its behavior. Most expected the Sun’s current magnetic cycle to reach its peak in 2012. Instead, the peak came more than a year later.

The broad outlines of the Sun’s magnetic cycle are fairly well understood.

The Sun is a giant, spinning ball. Because it’s made of gas, though, it doesn’t all turn at the same rate — it spins fastest at the equator, and slowest near the poles.

That difference causes the Sun’s magnetic field to get stretched and tangled. Lines of magnetic force poke through the surface, forming dark sunspots. And occasionally, the magnetic field “snaps,” creating a powerful outburst known as a flare.

On average, this magnetic activity reaches its peak every 11 years. When that happens, the magnetic field flips over and resets itself, beginning the cycle anew.

But when you probe the details, things get unpredictable. The length of a cycle averages 11 years, but it can vary by a couple of years either way. And no two cycles are the same intensity.

The current cycle illustrates the point. It reached its peak in April of last year — between one and two years later than expected. And it was the weakest cycle seen in more than a century.

Solar physicists have many ideas about why the solar cycle varies so much, but no consensus. They’re still trying to figure out how to predict our sometimes unpredictable Sun. We’ll have more about that tomorrow.


Script by Damond Benningfield, Copyright 2015

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