Word: interior
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...same time, hot gases, being lighter, rise from the interior to the surface, while cooler, heavier gases descend -- a process called convection (similar to what occurs in a hot oven). As a result of these massive convection currents and the differing rates of solar rotation, the magnetic lines of force begin wrapping around the sun like ropes. The wrapping action stretches the ropes and creates magnetic fields so strong that they repel the surrounding solar gases. In effect, this makes the magnetic regions lighter than the gases, and they begin to rise. Some reach the surface and become sunspots, dark...
...refine or revise this model, scientists must learn more about the interior structure and behavior of the sun. A new tool has evolved that should help them in their quest -- helioseismology, which, simply stated, involves "listening" to the interior of the sun as it bubbles, gurgles and swirls. The entire outer third of the sun is a seething ocean of gas, constantly churned by thermal convection. And convection, says astronomer John Harvey of the National Solar Observatory at Kitt Peak, "is a very noisy process. So the sun makes noise, just as a pot of water does as it boils...
These sound waves, or seismic waves, cannot travel in space because there is no air or other medium to carry them. So when the waves reach the surface of the sun from below, they bounce back into the interior, where the greater heat bends them toward the surface again. The result, says astronomer Robert Noyes of the Harvard-Smithsonian Center for Astrophysics, is a "sun ringing like a bell, but not one that is being struck by a clapper. Rather, it is vibrating somewhat like a bell suspended in a sandstorm, continuously struck by tiny grains of sand...
Just as seismologists describe the structure and nature of the earth's interior by studying seismic waves caused by earthquakes or explosions, astronomers are using helioseismology to learn more about the structure of the sun. Although still in its infancy, the new science has already led to several discoveries. Says NSO's Harvey: "It looks as if the frequencies of the oscillating waves vary with the solar cycle: they decreased a bit as the sun went toward solar minimum. Now we expect them to increase again...
...hull of the World Prodigy began washing up on the shore within hours. Even faster, the Bush Administration, which had been caught flat-footed by the Valdez's spill in Prince William Sound, sent in a team of high-level officials, including Environmental Protection Agency administrator William Reilly, Interior Secretary Manuel Lujan and several White House advisers. While there was no chance the calamity would match the worst-in-history damage in Alaska, the Rhode Island spill could still wreak environmental havoc. The ship was loaded with a relatively light fuel that will break up much faster than...