[institut] Seminar Katedre za astronomiju - 9. maj 2006

[Katedra za astronomiju]

               Seminar iz astronomije i astrofizike


               utorak, 9. maj. 2006. godine, u 18 sati
   u prostorijama Katedre za astronomiju, Matematicki fakultet



                        Alessandro M. Forte

GEOTOP - Departement des Sciences de la Terre et de l'Atmosphere
                 Universite du Quebec a Monteral



 "PERTURBATIONS IN EARTH'S ORBITAL PARAMETERS AND EARTH ROTATION DUE TO
                THERMAL CONVECTION IN EARTH'S MANTLE"



Abstract:
Changes in Earth's external shape due to the process of thermal
convection in Earth's mantle may have a large influence on variations in
Earth's obliquity and axial precession rate. Mantle convection may also
produce significant true polar wander on geological time scales. A new
numerical model of thermal convection, based on seismic tomographic images
of Earth's internal structure, will be used to predict variations
in Earth's dynamic ellipticity and inertia tensor in the geologic past.
Using the many-body orbital solution of Laskar et al [1993], we determine
the consequences of convection-induced variations in Earth flattening on
changes in Earth's orbital parameters. A spectral S-transform analysis of
the predicted orbital perturbations will be employed to discover whether
the changes in Earth's dynamical ellipticity are sufficiently large to
produce a resonant interaction with the planets Jupiter and Saturn, as
discovered in a previous study [Forte and Mitrovica, 1997]. This resonance
can strongly perturb Earth's precession rate and obliquity, yielding
significant changes in high-latitude summer insolation in the geologic
past. The impact of convection on Earth's inertia tensor will also be
considered from the perspective of paleomagnetic reconstructions of true
polar wander.



                                                         Dragana Ilic
                                                    astronom at matf.bg.ac.yu