The frequency of sunspots rises and falls during these cycles, and the start of a new cycle indicates they are likely to begin increasing.
Sunspots, areas of intense magnetic activity on the sun, can affect Earth by disrupting electrical grids, airline and military communications, GPS signals and even cell phones, the agency said. During periods of intense sunspot activity, known as solar storms, highly charged radiation from the sun may head toward Earth.
"Our growing dependence on highly sophisticated, space-based technologies means we are far more vulnerable to space weather today than in the past," said NOAA Administrator Conrad C. Lautenbacher, Jr.
Last April an international panel of solar experts forecast that Solar Cycle 24 would start in March 2008, plus or minus six months. The panel was split between those predicting a strong or weak cycle.
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On the Net:
Space Weather Prediction Center: http://www.swpc.noaa.gov
Solar Cycle forecast: http://www.noaanews.noaa.gov/stories2007/s2847.htm
