Word: fieldings
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Dates: during 1980-1989
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...content seemed to vary in rhythm with sunspot numbers. When sunspots were rare, as they were during the Maunder minimum, the amount of carbon 14 in the tree rings increased markedly; when they were numerous, the amount decreased. The explanation: during the sun's more active periods, its magnetic field, which ordinarily deflects some cosmic rays away from the earth, expands and becomes an even greater barrier to the rays. As a result, less carbon 14 is created in the atmosphere and less finds its way into trees...
Most explanations of that phenomenon liken the sun to a dynamo. Mighty currents of electricity flowing in the solar interior generate magnetic-field lines that, like the earth's, tend to be oriented in a north-south direction. But because the sun, unlike the earth, is gaseous, it does not rotate uniformly: bands of gases around the equator circle the solar axis once every 27 days, compared with a 34-day rotation rate near the poles...
While all that may be true, says Caltech physicist Robert Leighton, "if the sun didn't have a magnetic field, it would be as dull as most nighttime astronomers think it is." What a difference a field makes. Twisted and stretched by both the sun's rotation and its roiling interior, the magnetic lines of force orchestrate the intriguing solar cycle...
...wrapping and stretching of magnetic-field lines is also believed to be responsible for the spots' appearing progressively closer to the solar equator and the switch of magnetic polarities after each cycle. But ingenious as it seems, the dynamo model of the sun may need some serious revision. Astronomer Richard Altrock, at Sacramento Peak, has observed a brightening of the sun's corona that begins near the poles -- just when the first sunspots of a cycle break out around 35 degrees latitude -- then slowly progresses toward the equator. The brightening, he suspects, marks the beginning of still another cycle, long...
...telltale seismic-wave patterns also suggest that while the sun's outer layer rotates faster at the equator than at the poles, the inner region rotates uniformly. This creates a shear force, like the blades of scissors sliding past each other, that Harvey suspects distorts the magnetic field, giving rise to the solar cycle...