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Advances in Geosciences An open-access journal for refereed proceedings and special publications
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Volume 1
Adv. Geosci., 1, 103–108, 2003
https://doi.org/10.5194/adgeo-1-103-2003
© Author(s) 2003. This work is licensed under
the Creative Commons Attribution-NonCommercial-ShareAlike 2.5 License.
Adv. Geosci., 1, 103–108, 2003
https://doi.org/10.5194/adgeo-1-103-2003
© Author(s) 2003. This work is licensed under
the Creative Commons Attribution-NonCommercial-ShareAlike 2.5 License.

  30 Jun 2003

30 Jun 2003

Why the 18.6 year tide cannot explain the change of sign observed in j2

F. Deleflie1, P. Exertier1, G. Metris1, P. Berio1, O. Laurain1, J.-M. Lemoine2, and R. Biancale2 F. Deleflie et al.
  • 1Observatoire de la Côte d’Azur – CERGA/GRGS, Av. N. Copernic F-06130 Grasse, France
  • 2Observatoire Midi-Pyrénées OMP/GRGS, Av. E. Belin, F-31400 Toulouse, France

Abstract. Recent studies show a change, starting in 1998, in the behavior of the variation of the dynamical flattening of the Earth (J2), supposed to be constant (secular), and mainly due to the post glacial rebound effect. In this paper, we study to what extent this behavior can be correlated or not with the 18.6 year tide: with more than twenty years of tracking data on LAGEOS-1, that is to say more than a period of 18.6 years, this effect can now be separated from the secular variation. We use our theory of mean orbital motion, dedicated to studies of the long period effects on the orbital motion. We build one single arc of LAGEOS-1 from 1980 to 2002, which provides a continuous description of the orbital parameters. This is the great originality of our approach. We focus our attention on the ascending node of LAGEOS-1, and we show that the change observed in j2 cannot be attributed to a statistical error due to a correlation, in short arcs results, between the secular variation of J2 and the 18.6 year tide. The proof is based on the adjustment of amplitudes and phases of the long period tides, and on the shape of the residuals.

Key words. secular variation of J2, 18.6 year tide, mean orbital motione

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