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Not everyone agrees with Harvey's view, but further advances in helioseismology could resolve the issue. For example, the technique might help confirm or undermine a new idea that sunspots and flares are produced by giant cylindrical-shaped flows of hot material kept in motion by convection. Adjacent cylinders rotate in opposite directions in the 250,000-mile-deep solar convection zone and gradually migrate toward the equator. Like rollers in an old-fashioned washing machine, one proposal suggests, these cylinders squeeze magnetic fields and in effect wring out sunspots in the process.
For the continuous pursuit of helioseismology, uninterrupted when the sun dips below the horizon, the National Science Foundation is planning to commit $18 million toward a Global Oscillation Network Group, which sponsors hope will begin full operation in 1993. The program will link six helioseismological stations around the world so that the sun will, literally, never set on GONG. Oscillations will also be measured by a satellite that NASA and the European Space Agency plan to launch in the early 1990s.
One possible benefit that scientists could gain from these observations would be the ability to predict powerful flares, an art that will become increasingly important in the space age. While the only probable casualties of the approaching solar maximum will be satellites in low orbit, blown electrical transformers and some interrupted radio and television transmissions, future maximums could endanger humans venturing beyond the earth's protective magnetic field. Space travelers in high orbit, in interplanetary space or on the surface of the moon or another planet during maximums would be vulnerable to lethal radiation from high-energy particles hurled into space by solar flares. That threat has influenced plans for manned missions to Mars, which call for spacecraft with lead-lined "storm cellars," into which astronauts can duck if a dangerous solar flare appears or is anticipated.
Does the approaching solar maximum, or future ones, pose any threat to earthbound humans? Astronomer Eddy does not think so. "For the most part," he says, "the sun is a very benign, well-behaved, middle-age* star." Still, he muses, "it's not entirely regular. We have looked at the sun for such a small fraction of its life, we should not be at all surprised if it does something outside our experience."
Of one thing astronomers are sure: solar behavior will eventually change -- and drastically. When the sun runs low on hydrogen, it will swell into a red giant, ballooning out to engulf Mercury and perhaps Venus. Even if it does not expand far enough to swallow the earth, its radiant heat will boil away the oceans, leaving behind a dead, incinerated planet. But that cosmic calamity will not occur for about 5 billion years. That gives astronomers a fair amount of time to comprehend the still mysterious workings of the star closest to the earth.
FOOTNOTE: *To astronomers, the eastern edge of the sun is to the left, as viewed from earth.
FOOTNOTE: *If current theory is correct. But only about a third the number of neutrinos (particles with little or no mass that travel at the speed of light) that the sun should be producing at this temperature have been detected, leading some scientists to speculate that the core temperature is lower.