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Solar Dynamics Observatory: The 'Variable Sun' Mission

February 5, 2010: For some years now, an unorthodox idea has been gaining favor among astronomers. It contradicts old teachings and unsettles thoughtful observers, especially climatologists.

"The sun," explains Lika Guhathakurta of NASA headquarters in Washington DC, "is a variable star."

But it looks so constant...

That's only a limitation of the human eye. Modern telescopes and spacecraft have penetrated the sun's blinding glare and found a maelstrom of unpredictable turmoil. Solar flares explode with the power of a billion atomic bombs. Clouds of magnetized gas (CMEs) big enough to swallow planets break away from the stellar surface. Holes in the sun's atmosphere spew million mile-per-hour gusts of solar wind.

And those are the things that can happen in just one day.

Over longer periods of decades to centuries, solar activity waxes and wanes with a complex rhythm that researchers are still sorting out. The most famous "beat" is the 11-year sunspot cycle, described in many texts as a regular, clockwork process. In fact, it seems to have a mind of its own.

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