The coupling between inertial and rotational eigenmodes in planets with liquid cores
(2019) Geophysical Journal International — Vol. 218, n° 2, p. 1071-1086 (2019)
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- Authors
Triana, Santiago Andrés 
Dehant, Véronique
- Abstract
- The Earth is a rapidly rotating body. The centrifugal pull makes its shape resemblea flattened ellipsoid and Coriolis forces support waves in its fluid core, known asinertial waves. These waves can lead to global oscillations, or modes, of the fluid.Periodic variations of the Earth’s rotation axis (nutations) can lead to an exchange ofangular momentum between the mantle and the fluid core and excite these inertialmodes. In addition to viscous torques that exist regardless of the shape of theboundaries, the small flattening of the core-mantle boundary (CMB) allows inertialmodes to exert pressure torques on the mantle. These torques effectively couple therigid-body dynamics of the Earth with the fluid dynamics of the fluid core. Herewe present the first high resolution numerical model that solves simultaneously therigid body dynamics of the mantle and the Navier-Stokes equation for the liquidcore. This method takes naturally into account dissipative processes in the fluidthat are ignored in current nutation models. We find that the Free Core Nutation(FCN) mode, mostly a toroidal fluid flow if the mantle has a large moment of inertia,enters into resonance with nearby modes if the mantle’s moment of inertia is reduced.These mode interactions seem to be completely analogous to the ones discovered bySchmitt (2006) in a uniformly rotating ellipsoid with varying flattening
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Citations
Triana, S. A., Rekier, J., Trinh, A., & Dehant, V. (2019). The coupling between inertial and rotational eigenmodes in planets with liquid cores. Geophysical Journal International, 218(2), 1071-1086. https://doi.org/10.1093/gji/ggz212 (Original work published 2019)