Storm on the Sun

The coming sunspot cycle will be stronger than the previous one and could disrupt communications, interfere with GPS and bring down entire power systems

The next sunspot cycle will be a year late and as much as 50 percent stronger than the last one, according to a new forecast released last week by scientists from NASA and the National Science Foundation. Such predictions are vital because the solar storms associated with the sunspots not only endanger humans in space, but also can slow satellites in orbit, disrupt communications, interfere with GPS positioning and bring down power systems.

The most recent cycle, which peaked in 2001, was relatively weak with few significant disruptions reported. A major solar storm associated with the sunspot cycle on March 13, 1989 brought down the power grid in Quebec, darkening much of the province for nine hours.

The latest forecast was made using a sophisticated computer program developed by solar scientist Mausumi Dikpati of the National Center for Atmospheric Research in Boulder, Colorado, and her colleagues. The program is based on mapping of subsurface plasma flows discovered by NASA8217;s Solar and Heliospheric Observatory, which was launched in 2005. The satellite observatory uses sound waves in the sun8217;s interior to reveal the details of its structure, much as a doctor uses ultrasound to image internal organs.

Dikpati found that the solar cycle is powered by massive rivers of electromagnetic plasma flowing near the sun8217;s surface from its equator to the pole and back again. The flow of plasma is like a conveyor belt, carrying large quantities of plasma from the equator to the pole and back over a 22-year period, about twice the 11-year period of sunspot cycles. Dikpati8217;s findings were published in the March 3 edition of the journal Geophysical Research Letters.

Sunspots8212;first observed by Galileo in 16108212;are dark areas on the sun8217;s surface that are about 2,700 degrees Fahrenheit cooler than surrounding areas. They are caused by the eruption of magnetic fields through the sun8217;s surface, disrupting plasma and creating cool spots. How they were generated and what controlled their periodicity has been a matter of dispute since the cycle was discovered 150 years ago.

The magnetic eddies that break through the surface release enormous amounts of energy, sending sheets of ionised particle and ultraviolet radiation toward Earth. The particles can be dangerous to humans exposed to them in space and can disrupt not only electronic devices on satellites but even power grids on the ground. Heat from the ultraviolet emissions causes the Earth8217;s atmosphere to balloon slightly, increasing the drag on satellites in low-Earth orbit, including the International Space Station.

Forecasting the strength of sunspots is very important to satellite operators and many other businesses, said Joseph Kunches of the National Oceanic and Atmospheric Administration8217;s Space Environment Center in Boulder. Until now, however, such forecasts could be made only by extrapolating from past events, and those forecasts have not been very accurate. Dikpati and her colleagues 8216;8216;give us something better than we have ever had before,8217;8217; he said.

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Dikpati and her colleagues used characteristics of one sunspot cycle to predict the next. Looking backward over records from the past 12 sunspot cycles, she said, the team has been able to predict the timing and magnitude of each successive cycle with 98 percent accuracy. They predict that the next sunspot cycle, called cycle 24, will begin in late 2007 or early 2008 and will produce sunspots across an area slightly larger than 2.5 percent of the sun8217;s surface. The cycle is likely to reach its peak about 2012 before subsiding.

Los Angeles Times