2009 will go down as the sun’s third quietest year on record, under-shone only by 1913 and 2008.
Two hundred-sixty of the year’s 365 days (71 percent) were sunspotless. Last year saw 266 sunspotless days, while the sun had no spots on 311 of the days in 1913. It was only a very active December that kept 2009 from falling below last year’s mark.
Sunspot activity waxes and wanes in a roughly 11-year cycle, so hitting solar minima isn’t surprising. But what the numbers underscore is that we spent much of the year still in the midst of the deepest, longest solar minimum in a long time.
People keep their eyes on sunspots because their frequency and intensity is correlated with the overall level of solar activity. Changes in the sun’s energy flows can seriously impact conditions on Earth and our immediate environment in space. While a particularly active sun can generate geomagnetic storms that damage satellites and electrical grid infrastructure, a sun as quiet as the one of the last few years could affect the Earth’s climate, although not by much.
“If you want to understand all the drivers of Earth’s atmospheric system, you have to understand how sunspots emerge and evolve,” Matthias Rempel of NCAR’s High Altitude Observator told Wired.com for an earlier story.
http://www.wired.com/wiredscience/2009/12/the-year-in-sunspot/
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