 By LEE BOWMAN Scripps Howard News Service March 07, 2006
According to a new computer model tracking the long-term dynamics of magnetic energy as it moves around our star, along with historical analysis of sunspot activity, solar eruptions are more likely to disrupt communications, power grids and spacecraft. Solar cycles may also have subtle effects on long-term weather patterns on the Earth, although those influences are still poorly understood.
Astronomers have known for centuries that the number of sunspots (generated by magnetic storms bursting to the surface of the sun) peak roughly every 11 years, as the sun's internal dynamo reverses the magnetic field every 22 years. Scientists at the National Center for Atmospheric Research in Boulder, Colo., fed data from sunspot cycles going back to 1880 into the new model, and found that it accurately predicted what the sun would do over the past eight cycles. Essentially, the remnants of sunspots from one cycle sink back beneath the surface of the sun and, over about 20 years, are transported toward the sun's poles where they become "seeds" for sunspots that will erupt near the equator of the sun two cycles later. Sunspots are dark regions of concentrated magnetic fields on the surface of the sun, from which solar storms burst as the magnetic fields twist and snap. "It is the measure of this memory of past cycles that allows us to make a forecast,'' explained Mausumi Dikpati, leader of the forecast team at NCAR's High Altitude Observatory, which published its results in the current issue of the journal Geophysical Research Letters. While the NCAR model predicts that the upswing in solar storms will begin in late 2007 or early 2008, research by David Hathaway of NASA's Marshall Space Flight Center points to an earlier, rather than later, onset, perhaps beginning late this year or early 2007. "We're basing this on the fact that the large cycles tend to start early, and that's what happened with five of the last six big cycles,'' Hathaway said. Although the Earth's atmosphere shields humans and other life forms on the ground from the worst radiation and magnetic storm effects, the sun's eruptions can play havoc with a host of technology in space and on the ground. For starters, a more active sun can heat up and swell Earth's atmosphere, creating more drag on spacecraft in low orbit, including the International Space Station, complicating NASA's efforts to complete and supply the station with a dwindling number of space shuttle missions. Electrical and radiation surges in space can endanger unshielded astronauts and zap spacecraft electronics, while shifts in the upper atmosphere can jiggle signals from GPS satellites to the ground and fluctuations to Earth's magnetic field can generate current surges that can knock out power grids and damage pipelines. "Just as the seasonal forecasts of hurricanes can help guide emergency planners to expect a more active or less active than normal season, this kind of forecast ability helps us in alerting the agencies and industries that can be hit by space weather,'' said Joe Kunches, chief of the forecast and analysis branch at the Space Environment Center, in Boulder, part of the National Oceanic and Atmospheric Administration. The NCAR team is now working to extend the model to issue a forecast for solar activity 22 years into the future, or two cycles ahead. That active period for the sun is expected to peak in the 2020s, or about the time when the human missions to the moon or even Mars are projected to be under way.
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