Hur låter solen ?

Vibration

The sun vibrates like a bell that is continually struck. But the sun produces more than 10 million individual "tones" at the same time. The vibrations of the solar gas are mechanically similar to the vibrations of air -- also a gas -- that we know as sound waves. Astronomers therefore refer to the solar waves as sound waves, though the vibrations are much too slow for us to hear. The fastest solar vibrations have a period of about 2 minutes. A vibration's period is the amount of time taken for a complete cycle of vibration -- one back-and-forth movement of the vibrating object. The slowest vibration that a human being can hear has a period of about 1/20 of a second.

Most of the sun's sound waves originate in convection cells -- large concentrations, or clumps, of gas beneath the surface. These cells carry energy to the surface by rising, just as water boiling in a pan rises to the surface. The word convection refers to the boiling motions of the cells. As the cells rise, they cool. They then fall back down to the level at which the upward motion started. As the cells fall, they vibrate violently. The vibrations cause sound waves to move out from the cells.

Because the sun's atmosphere has so little mass, sound waves cannot travel through it. Therefore, when a wave reaches the surface, it turns back inward. As a result, a bit of the surface bobs up and down. As the wave travels inward, it begins to curve back toward the surface. The amount by which it curves depends on the density of the gas through which it travels and other factors. Eventually, the wave reaches the surface and turns inward again. It continues to travel until it loses all its energy to the surrounding gas.

The waves that travel downward the greatest distance have the longest periods. Some of these waves approach the sun's core and have periods of several hours.

http://www.nasa.gov/worldbook/sun_worldbook.html