HR: 0800h
AN: GP11D-0851    [Abstracts]
TI: Correlated Changes in the Length of a Day and the Magnetic Field with a Period of 60 Years
AU: Yu, Z
EM: zjyu@igpp.ucla.edu
AF: University of California Los Angeles, Institute of Geophysics and Planetary Physics, 405 Hilgard Ave., Los Angeles, CA 90095-1567 United States
AU: Roberts, P
EM: roberts@math.ucla.edu
AF: University of California Los Angeles, Institute of Geophysics and Planetary Physics, 405 Hilgard Ave., Los Angeles, CA 90095-1567 United States
AU: * Russell, C T
EM: ctrussell@igpp.ucla.edu
AF: University of California Los Angeles, Institute of Geophysics and Planetary Physics, 405 Hilgard Ave., Los Angeles, CA 90095-1567 United States
AB: The length of the day changes on many scales. Long-term changes occur as the surface of the Earth rebounds from glaciation. Very short-term variations occur in response to changes in the outer fluid envelopes of the Earth, the oceans and atmosphere. In between there appears to be at least one significant quasi-periodic variation with a 60-year period. A similar 60-year period is present in the Earth's magnetic field, leading to the speculation that the length of day variation with a 60-year period is due to periodic motion of the core of the Earth. We examine the variation of the length of the day, using Hilbert-Huang transformation to deduce intrinsic mode function and to separate out the behavior of the length of the day at periods near 60 years. We repeat for terrestrial magnetic field records and see similar behavior. Finally, we deduce the relative phase of the two variations at the 60-year period.
DE: 1507 Core processes (8115)
DE: 1560 Time variations--secular and long term
SC: Geomagnetism and Paleomagnetism [GP]
MN: 2004 AGU Fall Meeting