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Sunspots, dark cooler regions on the surface of the sun, all but disappeared in 2008 and 2009. Scientists now understand what happened. The two years reflected an unusually long time period of low solar activity. According to astronomers, the current solar cycle was supposed to create increasing activity as it builds toward the climax of an 11-year cycle.
Sunspots are highly magnetized globs of charged particles called plasma on the solar surface. Plasma circulates on the Sun in a movement called the “Great Conveyor Belt” that is much like ocean currents on the earth. The conveyor belt travels along the Sun’s surface, plunges inward around the poles and then re-emerges near the equator.
When sunspots start to decay, the surface currents gather up their demagnetized remains and drag them inside the sun where, at a depth of 187,000 miles, their magnetic field is recharged. The re-magnetized plasma then rises back up to the surface — and the sunspot is reborn.
After the sunspots were noticeably absent, Dibyendu Nandi of the Indian Institute of Science Education and Research in Kolkata and colleagues proposed a computer model to determine what happened to the sunspots. “According to our model, the trouble with sunspots actually began back in the late 1990s,” co-author Andres Munoz-Jaramillo of the Harvard-Smithsonian Center for Astrophysics said in a press release. “At that time, the conveyor belt sped up.” In other words, the Great Conveyor belt was moving way too fast for the sunspots to be fully re-magnetized down in the bowels of the sun.
The latest solar cycle began in 1996 and is likely to end in mid-2013, although a solar maximum, the solar cycle’s most active point, is usually preceded by a period of eruptions that can last as much as two and a half years, say experts. Last month, the solar flares caused auroras in northern skies and disrupted some radio communications, but damage to communications was limited because Earth’s alignment with a protective magnetic field.