[Previous] | [Session 4] | [Next]
R. Komm, R. Howe, B. Durney, F. Hill (NSO)
We present the temporal variation of the solar angular momentum derived from helioseismic observations. In the absence of `true' angular momentum inversions, we use the rotation rates resulting from rotation inversions of GONG data and the density distribution from a model of the Sun. We focus especially on the layers near the base of the convection zone and the layers near the solar surface. We derive the angular momentum as a function of depth and the corresponding solid-body rotation. The angular momentum decreases with increasing radius following essentially the product of density times the fourth power of radius. The tachocline can be identified as a local maximum in the radial gradient of the angular momentum and as a local maximum in the relative angular momentum after subtracting the contribution of the solid-body rotation. The angular momentum shows the strongest temporal variation near the tachocline. This variation is reminiscent of the 1.3-yr periodicity found in the equatorial rotation rate of the tachocline, which is not too surprising since the angular momentum of a spherical shell is heavily weighted toward the equator. We discuss the extension of this variation into the convection zone and into the radiative interior. In addition, we fit the rotation rates as functions of latitude with Legendre polynomials to cross-validate the numerical results and to draw conclusions about the zonal flows (`torsional oscillations') in the upper convection zone.
This work was supported by NASA Grant S-92698-F.
[Previous] | [Session 4] | [Next]
Bulletin of the American Astronomical Society, 34
© 2002. The American Astronomical Soceity.