 . Derived from observations by the LOWL instrument. The LOWL instrument was developed at the High Altitude Observatory of the National Center for
Atmospheric Research, Boulder, Colorado, by Steve Tomczyk and his collaborators. It is located at the
Mauna Loa Solar Observatory, Hawaii, and has been operating since February 1994. |
- In 1977, the sun's convective zone was determined on the basis of solar oscillations, to be twice as deep as originally thought, extending to a depth of 30% of the sun's radius. This value was refined to 28.7 percent in 1991.
- The sound speed and thus the propagation of the sound waves is affected by the composition of gases within the Sun. A helium abundance of 23%-26% by mass was determined in this way.
- Current computer models of the sun's interior are in agreement with the predictions of the solar oscillations. They can now be used to refine our knowledge of the sun's internal motions and structures.
About the image: - In 1981, helioseismology was used to show an inward decline of ~15% in the equatorial rotation rate as one moves from the surface to about half-way down toward the sun's center. This result is startling and has not yet been explained.
- Within the convective zone at higher latitudes, there is little variation of rotation with depth. The differential rotation with latitude is preserved throughout the convective zone.
- Differential rotation disappears at greater depths. The rotation rate become independent of latitude in the outer part of the radiative zone. Here the sun rotates like a solid body.
- Rotation at greater depths has not yet been observed.
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