Influence of liquid core dynamics on rotational modes

Motivated by understanding the liquid core dynamics of tidally deformed planets and moons, we present a study of incompressible flow driven by latitudinal libration within rigid triaxial ellipsoids. We first derive a laminar solution for the inviscid equations of motion under the assumption of uniform vorticity flow. This solution exhibits a resonance if the libration frequency matches the frequency of the spin-over inertial mode. Furthermore, we extend our model by introducing a reduced model of the effect of viscous Ekman layers in the limit of low Ekman number (Noir & Cébron, J. Fluid Mech., vol. 737, 2013, pp. 412–439). This theoretical approach is consistent with the results of Chan et al. (Phys. Earth Planet. Inter., vol. 187, 2011, pp. 404–415) and Zhang et al. (J. Fluid Mech., vol. 692, 2012, pp. 420–445) for spheroidal geometries. Our results are validated against systematic three-dimensional numerical simulations. In the second part of the paper, we present the first linear stability analysis of this uniform vorticity flow. To this end, we adopt different methods (Lifschitz & Hameiri, Phys. Fluids A, vol. 3, 1991, p. 2644; Gledzer & Ponomarev, Acad. Sci., USSR, Izv., Atmos. Ocean. Phys., vol. 13, 1977, pp. 565–569) that allow us to deduce upper and lower bounds for the growth rate of an instability. Our analysis shows that the uniform vorticity base flow is prone to inertial instabilities caused by a parametric resonance mechanism. This is confirmed by a set of direct numerical simulations. Applying our results to planetary settings, we find that neither a spin-over resonance nor an inertial instability can exist within the liquid core of the Moon, Io and Mercury.

Download Full-text

Gravity Variations and Ground Deformations Resulting from Core Dynamics

Surveys in Geophysics ◽

10.1007/s10712-021-09656-2 ◽

2021 ◽

Author(s):

Mathieu Dumberry ◽

Mioara Mandea

Keyword(s):

Inner Core ◽

Liquid Core ◽

List Type ◽

Dynamical Processes ◽

Ground Deformations ◽

Gravity Changes ◽

Global Gravity ◽

Core Dynamics ◽

Gravity Variations ◽

Harmonic Degree

Abstract Fluid motion within the Earth’s liquid outer core leads to internal mass redistribution. This occurs through the advection of density anomalies within the volume of the liquid core and by deformation of the solid boundaries of the mantle and inner core which feature density contrasts. It also occurs through torques acting on the inner core reorienting its non-spherical shape. These in situ mass changes lead to global gravity variations, and global deformations (inducing additional gravity variations) occur in order to maintain the mechanical equilibrium of the whole Earth. Changes in Earth’s rotation vector (and thus of the global centrifugal potential) induced by core flows are an additional source of global deformations and associated gravity changes originating from core dynamics. Here, we review how each of these different core processes operates, how gravity changes and ground deformations from each could be reconstructed, as well as ways to estimate their amplitudes. Based on our current understanding of core dynamics, we show that, at spherical harmonic degree 2, core processes contribute to gravity variations and ground deformations that are approximately a factor 10 smaller than those observed and caused by dynamical processes within the fluid layers at the Earth’s surface. The larger the harmonic degree, the smaller is the contribution from the core. Extracting a signal of core origin requires the accurate removal of all contributions from surface processes, which remains a challenge. Article Highlights Dynamical processes in Earth's fluid core lead to global gravity variations and surface ground deformations We review how these processes operate, how signals of core origin can be reconstructed and estimate their amplitudes Core signals are a factor 10 smaller than the observed signals; extracting a signal of core origin remains a challenge

Download Full-text

Synchrotron radiography characterization of the liquid core dynamics in a canonical two-fluid coaxial atomizer

International Journal of Multiphase Flow ◽

10.1016/j.ijmultiphaseflow.2019.03.006 ◽

2019 ◽

Vol 115 ◽

pp. 1-8 ◽

Cited By ~ 5

Author(s):

Nathanael Machicoane ◽

Julie K. Bothell ◽

Danyu Li ◽

Timothy B. Morgan ◽

Theodore J. Heindel ◽

...

Keyword(s):

Liquid Core ◽

Synchrotron Radiography ◽

Core Dynamics ◽

Two Fluid

Download Full-text

Reconstruction of neutrino interactions observed in a liquid-core fibre detector

Nuclear Instruments and Methods in Physics Research Section A Accelerators Spectrometers Detectors and Associated Equipment ◽

10.1016/s0168-9002(98)01084-5 ◽

1998 ◽

Vol 406 (2) ◽

pp. 195-212 ◽

Cited By ~ 3

Author(s):

K HOEPFNER

Keyword(s):

Liquid Core ◽

Neutrino Interactions ◽

Core Fibre

Download Full-text

Frontier concept of rabi chip for intelligent humanoid

Journal of Analytical Chromatography and Spectroscopy ◽

10.24294/jacs.v1i2.908 ◽

2018 ◽

Vol 1 (2) ◽

Author(s):

Preecha Yupapin ◽

Amiri I. S. ◽

Ali J. ◽

Ponsuwancharoen N. ◽

Youplao P.

Keyword(s):

Human Brain ◽

Brain Function ◽

Rabi Oscillation ◽

Liquid Core ◽

Brain Surface ◽

Dipole Oscillation ◽

On Chip ◽

The Brain ◽

Robotic Applications ◽

Atom System

The sequence of the human brain can be configured by the originated strongly coupling fields to a pair of the ionic substances(bio-cells) within the microtubules. From which the dipole oscillation begins and transports by the strong trapped force, which is known as a tweezer. The tweezers are the trapped polaritons, which are the electrical charges with information. They will be collected on the brain surface and transport via the liquid core guide wave, which is the mixture of blood content and water. The oscillation frequency is called the Rabi frequency, is formed by the two-level atom system. Our aim will manipulate the Rabi oscillation by an on-chip device, where the quantum outputs may help to form the realistic human brain function for humanoid robotic applications.

Download Full-text