Non-rigid contributions to the value of the dynamical ellipticity of the Earth

• Autores: Escapa, A.; Baenas, T.; Ferrándiz, J. M.
• Año de publicación: 2025
• Idioma: español castellano
• Tipo de recurso: documento de conferencia
• Materia: Ciencias Astronómicas; Dynamical ellipticity (H); Non-rigid Earth effects; Earth precession and nutation
• Institución: Universidad Nacional de La Plata

The dynamical ellipiticity of the Earth H plays a central role in the Earth precession and nutation motions. Its current standard value comes from IAU 2006 precession model and is incorporated in IERS Conventions (2010). A common approach to determine H numerically relies in consider just the precession of the Earth, since the available analytical models are more complete than the nutation ones. It entails that it is required to determine the second order contributions to the general precession in longitude, as done originally in Kinoshita & Souchay (1990). A part of such precession contributions is due to the non-rigid nature of the Earth. Specifically, nutation-nutation crossed terms -second order terms in the sense of perturbation theories - comes from the lunisolar torques and are sensible to the fluid core and elasticity of the Earth. In turn, mass redistribution of tidal origin contributes to the precession, also depending in the Love numbers values for the solid Earth and the oceans. Both of them are absent in the derived value of H in IAU 2006 precession model. Following the Hamiltonian approach, we present the basic guidelines in computing H considering those non-rigid effects and provide an updated value. Our approach also allows to FIx neatly the tidal system tide-free, zerofrequency, and mean tide in which H is provided, a question hitherto omitted but necessary considering nowadays needs of consistency.
Facultad de Ciencias Astronómicas y Geofísicas