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Science 29 March 2002:
Vol. 295. no. 5564, pp. 2435 - 2438
DOI: 10.1126/science.1068541
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Reports

Orbital Influence on Earth's Magnetic Field: 100,000-Year Periodicity in Inclination

Toshitsugu Yamazaki,1* Hirokuni Oda1

A continuous record of the inclination and intensity of Earth's magnetic field, during the past 2.25 million years, was obtained from a marine sediment core of 42 meters in length. This record reveals the presence of 100,000-year periodicity in inclination and intensity, which suggests that the magnetic field is modulated by orbital eccentricity. The correlation between inclination and intensity shifted from antiphase to in-phase, corresponding to a magnetic polarity change from reversed to normal. To explain the observation, we propose a model in which the strength of the geocentric axial dipole field varies with 100,000-year periodicity, whereas persistent nondipole components do not.

1 Institute for Marine Resources and Environment, Geological Survey of Japan, AIST, Tsukuba 305-8567, Japan.
*   To whom correspondence should be addressed. E-mail: toshi-yamazaki{at}aist.go.jp

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