Core–mantle topographic coupling: a parametric approach and implications for the formulation of a triaxial three-layered Earth rotation

Huifeng Zhang; Wenbin Shen

doi:10.1093/gji/ggab079

Core–mantle topographic coupling: a parametric approach and implications for the formulation of a triaxial three-layered Earth rotation

Geophysical Journal International ◽

10.1093/gji/ggab079 ◽

2021 ◽

Vol 225 (3) ◽

pp. 2060-2074

Author(s):

Huifeng Zhang ◽

Wenbin Shen

Keyword(s):

Earth Rotation ◽

Inner Core ◽

Normal Modes ◽

Outer Core ◽

Chandler Wobble ◽

Parametric Approach ◽

Layered Earth ◽

Fluid Core ◽

Adopted Model ◽

Topography Model

SUMMARY We propose a parametric approach to the topographic (TOP) coupling between the mantle and outer core for refinement of the latest triaxial three-layered Earth rotation theory. Based on three models of the core–mantle boundary (CMB) topography, we obtain the axial components of the TOP torque as −2.08 × 1019, −2.72 × 1018 and −1.97 × 1017 N m, respectively. Under the frame of the triaxial three-layered Earth rotation theory, we solve the corresponding periods of free core nutation as −(329.83 ± 28.12), −(457.54 ± ∼) and −(428.23 ± 1.09) mean solar days (d), respectively. The other three normal modes, namely, Chandler wobble, inner core wobble and free inner core nutation, are almost not affected by the TOP coupling of the CMB, their period values being 433.24, 2718.69 and 934.02 d, respectively. Calculations show that the TOP torque is highly sensitive to the adopted model of the topography, which is known to be robust. Taking into account the normal modes of the triaxial three-layered Earth rotation, the results of the CMB topography obtained by seismic tomography can be constrained in the future to a certain extent. In this study, considering the TOP coupling with the appropriate topography model, the estimates for the dynamic ellipticity ef of the fluid core lie between 0.0026340 and 0.0026430, values that are 3.56 % higher than the hydrostatic equilibrium value.

Spin rotation, Chandler wobble and free core nutation of isolated multi-layer pulsars

Proceedings of the International Astronomical Union ◽

10.1017/s1743921312024246 ◽

2012 ◽

Vol 8 (S291) ◽

pp. 392-392

Author(s):

Alexander Gusev ◽

Irina Kitiashvili

Keyword(s):

Neutron Star ◽

Differential Rotation ◽

Heat Dissipation ◽

Inner Core ◽

Outer Core ◽

Chandler Wobble ◽

Time Of Arrival ◽

Layer Model ◽

Free Core Nutation ◽

Rotation Pole

AbstractAt present time there are investigations of precession and nutation for very different celestial multi-layer bodies: the Earth (Getino 1995), Moon (Gusev 2010), planets of Solar system (Gusev 2010) and pulsars (Link et al. 2007). The long-periodic precession phenomenon was detected for few pulsars: PSR B1828-11, PSR B1557-50, PSR 2217+47, PSR 0531+21, PSR B0833-45, and PSR B1642-03. Stairs, Lyne & Shemar (2000) have found that the arrival-time residuals from PSR B1828-11 vary periodically with a different periods. According to our model, the neutron star has the rigid crust (RC), the fluid outer core (FOC) and the solid inner core (SIC). The model explains generation of four modes in the rotation of the pulsar: two modes of Chandler wobble (CW, ICW) and two modes connecting with free core nutation (FCN, FICN) (Gusev & Kitiashvili 2008). We are propose the explanation for all harmonics of Time of Arrival (TOA) pulses variations as precession of a neutron star owing to differential rotation of RC, FOC and crystal SIC of the pulsar PSR B1828-11: 250, 500, 1000 days. We used canonical method for interpretation TOA variations by Chandler Wobble (CW) and Free Core Nutation (FCN) of pulsar.The two - layer model can explain occurrence twin additional fashions in rotation pole motion of a NS: CW and FCN. In the frame of the three-layer model we investigate the free rotation of dynamically-symmetrical PSR by Hamilton methods. Correctly extending theory of SIC-FOC-RC differential rotation for neutron star, we investigated dependence CW, ICW, FCN and FICN periods from flatness of different layers of pulsar.Our investigation showed that interaction between rigid crust, RIC and LOC can be characterized by four modes of periodic variations of rotation pole: CW, retrograde Free Core Nutation (FCN), prograde Free Inner Core Nutation (FICN) and Inner Core Wobble (ICW). In the frame of the three-layer model we proposed the explanation for all pulse fluctuations by differential rotation crust, outer core and inner core of the neutron star and received estimations of dynamical flattening of the pulsar inner and outer cores, including the heat dissipation. We have offered the realistic model of the dynamical pulsar structure and two explanations of the feature of flattened of the crust, the outer core and the inner core of the pulsar.

Shear Properties of Earth's Inner Core

Annual Review of Earth and Planetary Sciences ◽

10.1146/annurev-earth-071521-063942 ◽

2021 ◽

Vol 50 (1) ◽

Author(s):

Hrvoje Tkalčić ◽

Sheng Wang ◽

Thanh-Son Phạm

Keyword(s):

Shear Wave ◽

Inner Core ◽

Normal Modes ◽

Outer Core ◽

Annual Review ◽

Publication Date ◽

Shear Properties ◽

Shear Wave Speed ◽

Earth’S Inner Core ◽

Shear Structure

Understanding how Earth's inner core (IC) develops and evolves, including fine details of its structure and energy exchange across the boundary with the liquid outer core, helps us constrain its age, relationship with the planetary differentiation, and other significant global events throughout Earth's history, as well as the changing magnetic field. Since its discovery in 1936 and the solidity hypothesis in 1940, Earth's IC has never ceased to inspire geoscientists. However, while there are many seismological observations of compressional waves and normal modes sensitive to the IC's compressional and shear structure, the shear waves that provide direct evidence for the IC's solidity have remained elusive and have been reported in only a few publications. Further advances in the emerging correlation-wavefield paradigm, which explores waveform similarities, may hold the keys to refined measurements of all inner-core shear properties, informing dynamical models and strengthening interpretations of the IC's anisotropic structure and viscosity. ▪ What are the shear properties of the inner core, such as the shear-wave speed, shear modulus, shear attenuation, and shear-wave anisotropy? Can the shear properties be measured seismologically and confirmed experimentally? Expected final online publication date for the Annual Review of Earth and Planetary Sciences, Volume 50 is May 2022. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates.

The Period of the Chandler Wobble

Symposium - International Astronomical Union ◽

10.1017/s0074180900032022 ◽

1980 ◽

Vol 78 ◽

pp. 187-193

Author(s):

F. A. Dahlen

Keyword(s):

Angular Momentum ◽

Inner Core ◽

Center Of Mass ◽

Angular Frequency ◽

Chandler Wobble ◽

Earth Model ◽

The Earth ◽

Fluid Core ◽

Relative Angular Momentum ◽

The Mean

Realistic models of the Earth are known to possess a solid anelastic inner core, mantle and crust, and a fluid core and oceans. How might we go about calculating the theoretical free period of the Chandler wobble of such an Earth model? Let xi be a set of Cartesian axes with an origin at the center of mass, and let ωi be the instantaneous angular velocity of rotation of these axes with respect to inertial space. The net angular momentum is then Cijωj + hi, where Cij is the inertia tensor, and hi is the relative angular momentum. Let us affix the axes xi in the mantle and crust by stipulating that the relative angular momentum is that of the core and oceans alone, i.e., hi (mantle and crust) = 0; hi = hi (core and oceans). For an infinitesimal free oscillation of angular frequency σ, we can write ωi = Ω(δi3 + mi eiσt), Cij = A(δilδjl + δi2δj2) + Cδi3δj3 + cij eiσt, and hi = hi eiσt, where Ω is the mean rate of rotation and A and C are the mean equatorial and polar moments of inertia.

Ohmic dissipation induced by Earth's nutation

10.5194/egusphere-egu2020-11740 ◽

2020 ◽

Author(s):

Santiago Triana ◽

Antony Trinh ◽

Jeremy Rekier ◽

Veronique Dehant

Keyword(s):

Magnetic Fields ◽

Inner Core ◽

Normal Modes ◽

Proof Of Concept ◽

Ohmic Dissipation ◽

Concept Model ◽

The Core ◽

Fluid Core ◽

Radio Signals ◽

Dynamical Treatment

Radio signals from distant quasars allow us to determine Earth's rotation variations with exquisite accuracy. These observations can be used to estimate the amplitudes, frequencies and damping constants associated with Earth's rotational modes, particularly the Free Core Nutation (FCN) and the Free Inner Core Nutation (FICN). These estimates suggest, however, fluid core viscosities many orders of magnitude higher than expected, or rms magnetic fields at the core-mantle boundary (CMB) incompatible with downward continuation of the observed surface field. Aiming at resolve this difficulty, we have developed a proof-of-concept model where we incorporate an approximate fluid-dynamical treatment of the core flow associated with the FCN and the FICN. We show that, at least for the FCN, no abnormally high viscosities or magnetic fields are required. The model might provide in fact a robust, independent estimate of the rms magnetic field strength in the fluid core. Additionally, the model illustrates the importance of considering inter-mode resonances involving inertial modes (i.e. Coriolis-restored) and the rotational normal modes.

Osmotic stress and vesiculation as key mechanisms controlling bacterial sensitivity and resistance to TiO2 nanoparticles

Communications Biology ◽

10.1038/s42003-021-02213-y ◽

2021 ◽

Vol 4 (1) ◽

Author(s):

Christophe Pagnout ◽

Angelina Razafitianamaharavo ◽

Bénédicte Sohm ◽

Céline Caillet ◽

Audrey Beaussart ◽

...

Keyword(s):

Lipid Peroxidation ◽

Osmotic Stress ◽

Inner Core ◽

Metal Oxide Nanoparticles ◽

Membrane Vesicles ◽

Outer Core ◽

Membrane Composition ◽

Cell Turgor ◽

Bacterial Sensitivity ◽

Membrane Components

AbstractToxicity mechanisms of metal oxide nanoparticles towards bacteria and underlying roles of membrane composition are still debated. Herein, the response of lipopolysaccharide-truncated Escherichia coli K12 mutants to TiO2 nanoparticles (TiO2NPs, exposure in dark) is addressed at the molecular, single cell, and population levels by transcriptomics, fluorescence assays, cell nanomechanics and electrohydrodynamics. We show that outer core-free lipopolysaccharides featuring intact inner core increase cell sensitivity to TiO2NPs. TiO2NPs operate as membrane strippers, which induce osmotic stress, inactivate cell osmoregulation and initiate lipid peroxidation, which ultimately leads to genesis of membrane vesicles. In itself, truncation of lipopolysaccharide inner core triggers membrane permeabilization/depolarization, lipid peroxidation and hypervesiculation. In turn, it favors the regulation of TiO2NP-mediated changes in cell Turgor stress and leads to efficient vesicle-facilitated release of damaged membrane components. Remarkably, vesicles further act as electrostatic baits for TiO2NPs, thereby mitigating TiO2NPs toxicity. Altogether, we highlight antagonistic lipopolysaccharide-dependent bacterial responses to nanoparticles and we show that the destabilized membrane can generate unexpected resistance phenotype.

On the reliability of PKIIKP phase identification at a single station

10.5194/egusphere-egu21-6554 ◽

2021 ◽

Author(s):

Olga Usoltseva ◽

Vladimir Ovtchinnikov

Keyword(s):

Inner Core ◽

Seismic Velocity ◽

Seismic Station ◽

Shear Velocity ◽

Outer Core ◽

Joint Analysis ◽

Time Range ◽

Model Parameters ◽

Phase Identification ◽

Single Station

Study of the contact zone between the inner and outer core represents considerable interest for understanding of properties, structures and dynamic of the Earth's core. One of the sources of the data about the processes proceeding in the top part of the inner core is the seismic wave PKIIKP once reflected from an undersize inner core boundary. Amplitudes of these waves are sensitive to the shear velocity in the top part of the inner core and are small. Therefore their identification at a single seismic station is not reliable without application of additional methods of analysis. Significant in this regard is the discussion about the source (in inner core or in mantle) of anomalous arrivals detected at the TAM station in North Africa [1,2] in the time range of PKIIKP phase.To estimate influence of model parameters (S and P seismic velocity) on the characteristics of PKIIKP wave (amplitude and travel time) we calculated sensitivity kernels for upper mantle and inner core for dominant period 1.2 s, azimuth step 0.2 degrees and radius step 20 km by using DSM Kernel Suite algorithm. It was revealed that PKIIKP amplitude is more sensitivities to mantle heterogeneities than to inner core ones. For reducing the effects of the overlying structures we suppose to use &#1072; joint analysis PKIIKP and pPKIIKP waves. With this approach, an incorrect identification of the PKIIKP wave is most likely excluded. We demonstrate the effectiveness of the approach on the example of processing the seismogram of the 11.02.2015 earthquake re&#1089;orded at the GZH station in China at a distance of 179.4 degrees.1. Wang W., Song X. Analyses of anomalous amplitudes of antipodal PKIIKP waves, EaPP. 2019. V. 3. P. 212-217. doi: 10.26464/epp20190232. Tsuboi S., Butler R. Inner core differential rotation inferred from antipodal seismic observations, PEPI, 2020. V.301. 106451.

Exotic collagen gradients in the byssus of the mussel Mytilus edulis.

Journal of Experimental Biology ◽

10.1242/jeb.198.3.633 ◽

1995 ◽

Vol 198 (3) ◽

pp. 633-644 ◽

Cited By ~ 6

Author(s):

X Qin ◽

J H Waite

Keyword(s):

Amino Acid ◽

Mytilus Edulis ◽

Tandem Repeats ◽

Inner Core ◽

Immunogold Labelling ◽

Outer Core ◽

Complementary Distribution ◽

Imino Acid ◽

Molecular Masses ◽

Straight Fiber

Byssal threads of the common mussel Mytilus edulis contain collagenous molecules from which two pepsin-resistant fragments have been isolated and characterized. These show a complementary distribution along the length of the thread, such that one predominates distally (Col-D) and the other proximally (Col-P). Both fragments contain three identical alpha-like chains with molecular masses of 50 kDa (Col-P) and 60 kDa (Col-D) and have typically collagenous amino acid compositions; for example, 35% glycine and almost 20% proline plus 4-trans-hydroxyproline. Hydroxylysine and 3-hydroxyproline were absent. Col-P sequences are also typical of collagen in consisting of tandem repeats of the triplet Gly-X-Y in which X and Y generally represent any amino acid. When proline occurs, it is hydroxylated to 4-trans-hydroxyproline only in the Y position. Seven instances where X is glycine have been detected in Col-P. Specific polyclonal anti-Col antibodies were used to isolate the precursors of Col-P and Col-D from the mussel foot. PreCol-P has a molecular mass of 95 kDa and contains 36% glycine but a lower imino acid content (13%). It has a complementary distribution with another precursor (preCol-D, 97 kDa) along the length of the foot. The two precursor compositions suggest resilin-like and silk-fibroin-like structures, respectively, in the noncollagenous domains of preCol-P and preCol-D. Immunogold labelling studies indicate that Col-P is associated with the coiled fibers of the inner core in the proximal portion of the thread, whereas Col-D is localized to the straight fiber bundles of the distal thread as well as to the outer core of the proximal thread.

Multiple inner core reflections from a Novaya Zemlya explosion

Bulletin of the Seismological Society of America ◽

10.1785/bssa0620041063 ◽

1972 ◽

Vol 62 (4) ◽

pp. 1063-1071 ◽

Cited By ~ 2

Author(s):

R. D. Adams

Keyword(s):

Lower Bound ◽

Inner Core ◽

Nuclear Explosion ◽

Outer Core ◽

Low Velocity ◽

Mantle Boundary ◽

Core Mantle Boundary ◽

Novaya Zemlya ◽

The Core ◽

Velocity Channel

Abstract The phases P2KP, P3KP, and P4KP are well recorded from the Novaya Zemlya nuclear explosion of October 14, 1970, with the branch AB at distances of up to 20° beyond the theoretical end point A. This extension is attributed to diffraction around the core-mantle boundary. A slowness dT/dΔ = 4.56±0.02 sec/deg is determined for the AB branch of P4KP, in excellent agreement with recent determinations of the slowness of diffracted P. This slowness implies a velocity of 13.29±0.06 km/sec at the base of the mantle, and confirms recent suggestions of a low-velocity channel above the core-mantle boundary. There is evidence that arrivals recorded before the AB branch of P2KP may lie on two branches, with different slownesses. The ratio of amplitudes of successive orders of multiple inner core reflections gives a lower bound of about 2200 for Q in the outer core.

Ohmic and viscous damping of the Earth's Free Core Nutation

10.5194/egusphere-egu21-12492 ◽

2021 ◽

Author(s):

Santiago Triana ◽

Jeremy Rekier ◽

Antony Trinh ◽

Veronique Dehant ◽

Ping Zhu

Keyword(s):

Effective Viscosity ◽

Inner Core ◽

Extreme Values ◽

Ohmic Heating ◽

Outer Core ◽

Viscous Damping ◽

Asymptotic Regime ◽

Free Core Nutation ◽

Numerical Studies ◽

Dissipation Processes

The cause for the damping of the Earth's Free Core Nutation (FCN) and the Free Inner Core Nutation (FICN) eigenmodes has been a matter of debate since the earliest reliable estimations from nutation observations were made available. Numerical studies are difficult given the extreme values of some of the parameters associated with the Earth's fluid outer core, where important dissipation processes can take place. We present a linear numerical model for the FCN that includes viscous dissipation and Ohmic heating. We find an asymptotic regime, appropriate for Earth's parameters, where viscous and Ohmic processes contribute equally to the total damping, with the dissipation taking place almost exclusively in the boundary layers. By matching the observed nutational damping we infer an enhanced effective viscosity matching and validating methods from previous studies. We suggest that turbulence caused by the Earth's precession can be a source for the FCN's damping.&#160;

Torsional waves driven by convection and jets in Earth’s liquid core

Geophysical Journal International ◽

10.1093/gji/ggy416 ◽

2018 ◽

Vol 216 (1) ◽

pp. 123-129 ◽

Cited By ~ 2

Author(s):

R J Teed ◽

C A Jones ◽

S M Tobias

Keyword(s):

Magnetic Field ◽

Density Gradient ◽

Inner Core ◽

Liquid Core ◽

Outer Core ◽

Dynamo Action ◽

Radial Magnetic Field ◽

Torsional Waves ◽

Plausible Mechanism ◽

Rich Liquid

SUMMARY Turbulence and waves in Earth’s iron-rich liquid outer core are believed to be responsible for the generation of the geomagnetic field via dynamo action. When waves break upon the mantle they cause a shift in the rotation rate of Earth’s solid exterior and contribute to variations in the length-of-day on a ∼6-yr timescale. Though the outer core cannot be probed by direct observation, such torsional waves are believed to propagate along Earth’s radial magnetic field, but as yet no self-consistent mechanism for their generation has been determined. Here we provide evidence of a realistic physical excitation mechanism for torsional waves observed in numerical simulations. We find that inefficient convection above and below the solid inner core traps buoyant fluid forming a density gradient between pole and equator, similar to that observed in Earth’s atmosphere. Consequently, a shearing jet stream—a ‘thermal wind’—is formed near the inner core; evidence of such a jet has recently been found. Owing to the sharp density gradient and influence of magnetic field, convection at this location is able to operate with the turnover frequency required to generate waves. Amplified by the jet it then triggers a train of oscillations. Our results demonstrate a plausible mechanism for generating torsional waves under Earth-like conditions and thus further cement their importance for Earth’s core dynamics.