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| Titel |
Effects of the observed J2 variations on the Earth’s precession and nutation |
| VerfasserIn |
José M. Ferrándiz, Tomás Baenas, Santiago Belda |
| Konferenz |
EGU General Assembly 2016
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| Medientyp |
Artikel
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| Sprache |
en
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 18 (2016) |
| Datensatznummer |
250130229
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| Publikation (Nr.) |
 EGU/EGU2016-10452.pdf |
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| Zusammenfassung |
| The Earth’s oblateness parameter J2 is closely related to the dynamical ellipticity H, which
factorizes the main components of the precession and the different nutation terms. In most
theoretical approaches to the Earth’s rotation, with IAU2000 nutation theory among them, H
is assumed to be constant. The precession model IAU2006 supposes H to have a
conventional linear variation, based on the J2 time series derived mainly from satellite laser
ranging (SLR) data for decades, which gives rise to an additional quadratic term of the
precession in longitude and some corrections of the nutation terms. The time evolution of J2
is, however, too complex to be well approximated by a simple linear model. The effect of
more general models including periodic terms and closer to the observed time series,
although still unable to reproduce a significant part of the signal, has been seldom
investigated.
In this work we address the problem of deriving the effect of the observed J2 variations
without resorting to such simplified models. The Hamiltonian approach to the Earth rotation
is extended to allow the McCullagh’s term of the potential to depend on a time-varying
oblateness. An analytical solution is derived by means of a suitable perturbation method in
the case of the time series provided by the Center for Space Research (CSR) of the University
of Texas, which results in non-negligible contributions to the precession-nutation angles. The
presentation focuses on the main effects on the longitude of the equator; a noticeable
non-linear trend is superimposed to the linear main precession term, along with some
periodic and decadal variations. |
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