For the past 3 centuries, the sun has followed a regular and reliable cycle. Every 11 years, it experiences a peak and a valley in its activity, called the maximum and minimum, respectively. During maxima, there are numerous sunspots (cool and dark areas on the sun's surface), the polarity of the sun's magnetic field weakens and then flips, and the solar wind fluctuates wildly. During minima, the sun is relatively placid, with no sunspots, a steady and strong magnetic field, and a more-or-less constant solar wind.
As of today, the solar minimum continues, as deep and as quiet as scientists have ever seen. And there remains significant disagreement within the panel, with a large minority still unconvinced that the new prediction is right. Read more
"We're experiencing a very deep solar minimum," says solar physicist Dean Pesnell of NASA’s Goddard Space Flight Center in Greenbelt, Md. In 2008, no sunspots were observed on 266 of the year's 366 days (73 percent). Sunspot counts for 2009 have dropped even lower, percentage-wise. As of March 31st, there were no sunspots on 78 of the year's 90 days (87 percent).
Sunspots are planet-sized islands of magnetism on the surface of the sun, and they are sources of solar flares, coronal mass ejections, and intense UV radiation. The sun has a natural cycle of about 11 years of high and low sunspot activity. This was discovered by German astronomer Heinrich Schwabe in the mid-1800s. Plotting sunspot counts, Schwabe saw that peaks of solar activity were always followed by valleys of relative calm—a clockwork pattern that has held true for more than 200 years.
In a way, the calm is exciting, says Pesnell. "For the first time in history, we're getting to observe a deep solar minimum." A fleet of spacecraft — including the Solar and Heliospheric Observatory (SOHO), the twin probes of the Solar Terrestrial Relations Observatory (STEREO), and several other satellites — are all studying the sun and its effects on Earth. Using technology that didn't exist 100 years ago
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