HR: 0800h
AN: P51C-0668    [Abstracts]
TI: A substantiation of cyclic process of the system Earth–Moon-Sun tidal evolution
AU: * Avsyuk, Y
EM: avsyuk@ifz.ru
AF: Institute for Physics of the Earth, RAS, Bol. Gruzinskaya, 10, Moscow, 123995, Russian Federation
AB: The present-day knowledge of the Earth and thorough description of the tidal force affecting the system Earth–Moon-Sun permits us to work out in detail a tidal evolution model. Thus we get a possibility to reconstruct global variations of the climate. The tidal evolution of natural processes on the Earth that has a huge satellite (the Moon mass is only 81 times less than the Earth mass) essentially differs from the evolution on a planet that has no satellite. There are some natural processes that are well-known in astrometry and geophysics but disregarded by experts in geodynamics and geotectonics. The movement of the rotation axis in the Earth's body is discovered more a century ago, but there is no a model explaining the mechanism of this process. Our predecessors emphasized importance of the discovery and suggested desire of such a model. G.H.Darwin in his comments on "Z–term" in the latitude variation wrote this movement could be due to alternate displacement of the Earth center. To explain the scale of that phenomena it is enough to adopt a displacement of the Earth center by twelve feet. A question is to the point is whether the Earth axis movement concerns with the Inner core (IC) displacements. There are some reasons testifying to forced movements of the IC. To understand the forcing influence one must not simplify the Earth's real orbital movement. In fact the system Earth–Moon rotates around the Sun with the period of year. The ecliptic is a plane containing the orbit of the Earth and the Moon mass center (barycenter). The Sun attraction is balanced dynamically in the barycenter but not in the Earth center. As a result, the Earth rotates just as the Moon round the barycenter with the period of the Moon month, and therefore the IC is subjected to a variable tidal force (1910). Newton in Append. XXV, problem VI, underlined that inasmuch as the Earth and the Moon rotate round their common mass center, the Earth movement is disturbed with similar forces. Laplace formula describes imperfectly the tidal force. One should not ignore perturbation terms. The first model was proposed by Kelvin and worked out in detail by G.H.Darwin. The model became a classic part of scientific and educational literature but without perturbations in the Earth orbit by the Sun. Provided the principal conception of the tidal evolution model is kept, we defined more accurately a model of the Earth structure and its orbital perturbations. The gravity variations due to the IC displacements are of the same order as the Moon tidal effect without perturbations. The both effects influence similarly the ocean currents and the hydrosphere dynamical figure. One can compare the model above with data of historical geology. Climatologists distinguish at least three epochs: transitions Algonk–Cambrian and Carbon–Perm, and Quaternary. Duration of mid-glaciations is of 200–250 Myear. Taken this value for the cycle duration and 2×1012 W for the power of variability of the rotation kinetic energy, one can estimate ranges of variation: ±4R for the Earth–Moon distance, ±6° for the ecliptic tilt, and 3.8×1018 erg/s for the power of the IC moves the outer liquids. Our studies are now at a first stage. The aim of the presentation is to show untapped possibilities in the tidal evolution model. Its updating bases on the data that were absent before and must be taken now into account for a discussion of ideas of historical geology and paleomagnetism.
DE: 1213 Earth's interior: dynamics (1507, 7207, 7208, 8115, 8120)
DE: 1507 Core processes (1213, 8115)
SC: Planetary Sciences [P]
MN: 2007 Fall Meeting