The next sunspot cycle will be 30 percent to 50 percent stronger than the previous one and begin as much as a year late, National Center for Atmospheric Research (NCAR) announced March 6.

The sun undergoes cycles from peak storm activity to quiet and back again that runs about 11 years. Forecasting the cycle may help anticipate solar storms, which can disrupt communications and power systems and affect the orbits of satellites, NCAR said, but solar scientists have tracked the cycles for some time without being able to predict their relative intensity or timing.

In a series of test runs, a newly developed computer model, known as the Predictive Flux-transport Dynamo Model, simulated the strength of the past eight solar cycles with more than 98 percent accuracy. The forecasts are generated, in part, by tracking the subsurface movements of the sunspot remnants of the previous two solar cycles. By analyzing recent solar cycles, the scientists also hope to forecast sunspot activity two solar cycles, or 22 years, into the future.

The next solar cycle, known as Cycle 24, will produce sunspots across an area slightly larger than 2.5 percent of the visible surface of the Sun. The scientists expect the cycle to begin in late 2007 or early 2008, about six 12 months later than a cycle would normally start. Cycle 24 is likely to reach its peak about 2012. The NCAR team plans to issue in 2007 a forecast of Cycle 25, which will peak in the early 2020s.

The NCAR team received funding from the National Science Foundation and NASA‘s Living with a Star program.