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Science 18 June 1993:
Vol. 260. no. 5115, pp. 1778 - 1781
DOI: 10.1126/science.260.5115.1778
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Articles

Observations of Time Variation in the Sun's Rotation

M. F. Woodard 1 and K. G. Libbrecht 1

1 Big Bear Solar Observatory, 264-33, California Institute of Technology, Pasadena, CA 91125

Observations of solar p-mode frequency splittings obtained at Big Bear Solar Observatory in 1986 and during 1988-90 reveal small (sim1 percent) changes in the sun's subsurface angular velocity with solar cycle. An asymptotic inversion of the splitting data yields the latitude dependence of the rotation rate and shows that the largest changes in the angular velocity, ap4 nanohertz, occurred between 1986 and the later years, at high (ap60°) solar latitudes. Earlier helioseismic observations suggest that solar cycle changes in the ratio of magnetic to turbulent pressure in the solar convection zone are large enough to account for the magnitude of the observed angular velocity variations but a detailed model of the phenomenon does not exist.

Submitted on March 22, 1993
Accepted on May 27, 1993

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Science. ISSN 0036-8075 (print), 1095-9203 (online)