Effects of density stratification on the frequencies of the inertial-gravity modes of the Earth's fluid core

Seyed-Mahmoud, B.; Moradi, Ali; Kamruzzaman, Md.; Naseri, Hossein

doi:10.1093/gji/ggv215

Cited by 5 publications

(2 citation statements)

References 20 publications

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“…The polynomial method is probably not well adapted to compute the highest-frequency (acoustic or gravity) modes, which exhibit localized structures that are already well described by ray theory [92,93]. Yet, it could be used to compute the lowest-frequency inertial-gravity modes [94] that can have larger-scale components [[95], in spheres]. Moreover, the inertial-gravity modes are known to be the preferred modes for nonlinear couplings with tidal flows in rotating stratified interiors [96,97], but the Boussinesq results remain to be extended with compressibility.…”

Section: Discussionmentioning

confidence: 99%

Acoustic and inertial modes in planetary-like rotating ellipsoids

Vidal

Cébron

2020

Proc. R. Soc. A.

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The bounded oscillations of rotating fluid-filled ellipsoids can provide physical insight into the flow dynamics of deformed planetary interiors. The inertial modes, sustained by the Coriolis force, are ubiquitous in rapidly rotating fluids and Vantieghem (2014, Proc. R. Soc. A , 470 , 20140093. doi:10.1098/rspa.2014.0093 ) pioneered a method to compute them in incompressible fluid ellipsoids. Yet, taking density (and pressure) variations into account is required for accurate planetary applications, which has hitherto been largely overlooked in ellipsoidal models. To go beyond the incompressible theory, we present a Galerkin method in rigid coreless ellipsoids, based on a global polynomial description. We apply the method to investigate the normal modes of fully compressible, rotating and diffusionless fluids. We consider an idealized model, which fairly reproduces the density variations in the Earth’s liquid core and Jupiter-like gaseous planets. We successfully benchmark the results against standard finite-element computations. Notably, we find that the quasi-geostrophic inertial modes can be significantly modified by compressibility, even in moderately compressible interiors. Finally, we discuss the use of the normal modes to build reduced dynamical models of planetary flows.

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Section: Discussionmentioning

confidence: 99%

Acoustic and inertial modes in planetary-like rotating ellipsoids

Vidal

Cébron

2020

Proc. R. Soc. A.

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“…The fourth approach is based on the Galerkin method. This Galerkin method was first used in studying the inertial modes of a compressible and stratified fluid core with rigid boundaries (Seyed-Mahmoud 1994;Seyed-Mahmoud et al 2007, 2015 with the 3-Potential description, the free wobble/nutation modes of a simple Earth model with a rotating, inviscid, homogeneous and incompressible fluid core contained in a spherical shell with rigid boundaries (Seyed-Mahmoud et al 2017). tried first to apply the stratified Galerkin method which is also called as the spectral element method (Karniadakis & Sherwin 2013), to study FCN period for a more real Earth model (PREM), and their calculated FCN period is 435 Sd, neither increasing the CMB ellipticity from its hydrostatic values as mentioned above, nor assuming of the geomagnetic contribution.…”

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confidence: 99%

A Spectral Element Method to Compute Earth’s Free Core Nutation

Zhang

Huang

2023

Res. Astron. Astrophys.

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The Free Core Nutation (FCN) is a rotational mode caused by non-alignment of the rotation axis of the core and of the mantle. Its period observed by VLBI and superconducting gravimetry is around 430 sidereal days (Sd) with precision of better than 1 Sd, while its "theoretical" period calculated by traditional approaches and a given Earth model ranges from 450 to 470 Sd. Their gap of about 30 Sd is significant comparing with its observation precision. We propose a spectral element method to compute the period of FCN and obtain a period of 434 Sd which is very close to the observed value.

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Inertial modes of an Earth model with a compressible fluid core and elastic mantle and inner core

Kamruzzaman

Seyed-Mahmoud

2019

J Geod

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Effects of density stratification on the frequencies of the inertial-gravity modes of the Earth's fluid core

Cited by 5 publications

References 20 publications

Acoustic and inertial modes in planetary-like rotating ellipsoids

Acoustic and inertial modes in planetary-like rotating ellipsoids

A Spectral Element Method to Compute Earth’s Free Core Nutation

Inertial modes of an Earth model with a compressible fluid core and elastic mantle and inner core

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