The Experts below are selected from a list of 258 Experts worldwide ranked by ideXlab platform

Paul H Roberts - One of the best experts on this subject based on the ideXlab platform.

  • generation of a strong magnetic field using uniform heat flux at the surface of the Core
    Nature Geoscience, 2009
    Co-Authors: Ataru Sakuraba, Paul H Roberts
    Abstract:

    Numerical simulations that assume realistic Core-Fluid viscosities have been unsuccessful in fully reproducing the unique characteristics of the Earth’s geomagnetic field. An evaluation of boundary conditions suggests that the prescription of a uniform heat flux at the Core’s surface could generate a more Earth-like magnetic field.

  • Generation of a strong magnetic field using uniform heat flux at the surface of the Core
    Nature Geoscience, 2009
    Co-Authors: Ataru Sakuraba, Paul H Roberts
    Abstract:

    The Earth’s main magnetic field is thought to be generated by motions in the planet’s Fluid outer Core, which lead to an effect similar to that of a dynamo^ 1 , 2 , 3 . Recent high-resolution numerical simulations produce only a non-dipolar^ 4 or a dipolar but comparatively weak magnetic field^ 5 , 6 unlike that of the Earth. Older models that did generate a strong, Earth-like field needed to use unrealistically high viscosities for the Core Fluid^ 7 , 8 , 9 , 10 . Common to most of the models is the assumption of a laterally uniform Core-surface temperature. Here we use a low-viscosity geodynamo model to evaluate the effect of a different and more realistic boundary condition—a uniform heat flux at the surface of the Core—on the simulation of an Earth-like magnetic field. Our results show that when the surface temperature is laterally uniform, only a weak magnetic field is generated because planetary-scale Fluid circulations are suppressed. In contrast, a laterally uniform heat flux at the Core’s surface leads to large-scale convective flows, and a comparatively strong dipole-type magnetic field. Contrary to previous work^ 11 , 12 , we suggest that thermal conditions at the Core surface have a strong effect on low-viscosity geodynamo models. Numerical simulations that assume realistic Core-Fluid viscosities have been unsuccessful in fully reproducing the unique characteristics of the Earth’s geomagnetic field. An evaluation of boundary conditions suggests that the prescription of a uniform heat flux at the Core’s surface could generate a more Earth-like magnetic field.

Ataru Sakuraba - One of the best experts on this subject based on the ideXlab platform.

  • generation of a strong magnetic field using uniform heat flux at the surface of the Core
    Nature Geoscience, 2009
    Co-Authors: Ataru Sakuraba, Paul H Roberts
    Abstract:

    Numerical simulations that assume realistic Core-Fluid viscosities have been unsuccessful in fully reproducing the unique characteristics of the Earth’s geomagnetic field. An evaluation of boundary conditions suggests that the prescription of a uniform heat flux at the Core’s surface could generate a more Earth-like magnetic field.

  • Generation of a strong magnetic field using uniform heat flux at the surface of the Core
    Nature Geoscience, 2009
    Co-Authors: Ataru Sakuraba, Paul H Roberts
    Abstract:

    The Earth’s main magnetic field is thought to be generated by motions in the planet’s Fluid outer Core, which lead to an effect similar to that of a dynamo^ 1 , 2 , 3 . Recent high-resolution numerical simulations produce only a non-dipolar^ 4 or a dipolar but comparatively weak magnetic field^ 5 , 6 unlike that of the Earth. Older models that did generate a strong, Earth-like field needed to use unrealistically high viscosities for the Core Fluid^ 7 , 8 , 9 , 10 . Common to most of the models is the assumption of a laterally uniform Core-surface temperature. Here we use a low-viscosity geodynamo model to evaluate the effect of a different and more realistic boundary condition—a uniform heat flux at the surface of the Core—on the simulation of an Earth-like magnetic field. Our results show that when the surface temperature is laterally uniform, only a weak magnetic field is generated because planetary-scale Fluid circulations are suppressed. In contrast, a laterally uniform heat flux at the Core’s surface leads to large-scale convective flows, and a comparatively strong dipole-type magnetic field. Contrary to previous work^ 11 , 12 , we suggest that thermal conditions at the Core surface have a strong effect on low-viscosity geodynamo models. Numerical simulations that assume realistic Core-Fluid viscosities have been unsuccessful in fully reproducing the unique characteristics of the Earth’s geomagnetic field. An evaluation of boundary conditions suggests that the prescription of a uniform heat flux at the Core’s surface could generate a more Earth-like magnetic field.

J. Vidal - One of the best experts on this subject based on the ideXlab platform.

  • Pressure torque of torsional Alfvén modes acting on an ellipsoidal mantle
    Geophysical Journal International, 2020
    Co-Authors: F Gerick, Dominique Jault, J. Noir, J. Vidal
    Abstract:

    We investigate the pressure torque between the Fluid Core and the solid mantle arising from magnetohydrodynamic modes in a rapidly rotating planetary Core. A 2-D reduced model of the Core Fluid dynamics is developed to account for the non-spherical Core-mantle boundary. The simplification of such a quasi-geostrophic model rests on the assumption of invariance of the equatorial components of the Fluid velocity along the rotation axis. We use this model to investigate and quantify the axial torques of linear modes, focusing on the torsional Alfvén modes (TM) in an ellipsoid. We verify that the periods of these modes do not depend on the rotation frequency. Furthermore, they possess angular momentum resulting in a net pressure torque acting on the mantle. This torque scales linearly with the equatorial ellipticity. We estimate that for the TM calculated here topographic coupling to the mantle is too weak to account for the variations in the Earth's length-of-day.

Luis J. Gallego - One of the best experts on this subject based on the ideXlab platform.

  • A molecular dynamics study of the collective correlation functions of a hard‐Core Fluid with a Yukawa tail
    The Journal of Chemical Physics, 1996
    Co-Authors: M. M. G. Alemany, C. Rey, Luis J. Gallego
    Abstract:

    We present a molecular dynamics study of the collective correlation functions of a hard‐Core system with an attractive Yukawa tail, for various thermodynamic states in the Fluid and liquid regions of the phase diagram. The results are compared with available information for hard spheres. The small‐q behavior of the intermediate scattering functions indicates the propagation of sound waves, i.e., phononlike collective excitations, in the hard‐Core Yukawa system. The upper limit of q for these collective modes is practically independent of the thermodynamic state. The computed transverse current correlation functions show that at liquid densities the hard‐Core Yukawa system is able to sustain shear wave propagation above a critical q; the upper limit of q for sound waves and the lower limit for shear waves nearly coincide. All of these features are qualitatively similar to those found for hard spheres. However, there are significant quantitative differences, which reflect the influence of the attractive Yuk...

  • Properties of a hard‐Core Fluid with a Yukawa tail studied by molecular dynamics and the mean spherical approximation
    The Journal of Chemical Physics, 1992
    Co-Authors: C. Rey, Luis J. Gallego, Luis E. Gonzalez
    Abstract:

    A molecular dynamics simulation method for computing the static and dynamic properties of a hard‐Core Fluid with a Yukawa tail is developed. The calculated static bulk properties show good agreement with the Monte Carlo results previously reported. We have also calculated the thermodynamic properties within the mean spherical approximation by the energy, compressibility, and virial routes; the ‘‘exact’’ data are most closely approximated by the energy route. The computed values of the self‐diffusion constant are compared with those corresponding to a hard‐sphere Fluid; the results are consistent with previous findings that the cohesive part of the intermolecular potential plays a significant role in reducing diffusion.

C. Rey - One of the best experts on this subject based on the ideXlab platform.

  • A molecular dynamics study of the collective correlation functions of a hard‐Core Fluid with a Yukawa tail
    The Journal of Chemical Physics, 1996
    Co-Authors: M. M. G. Alemany, C. Rey, Luis J. Gallego
    Abstract:

    We present a molecular dynamics study of the collective correlation functions of a hard‐Core system with an attractive Yukawa tail, for various thermodynamic states in the Fluid and liquid regions of the phase diagram. The results are compared with available information for hard spheres. The small‐q behavior of the intermediate scattering functions indicates the propagation of sound waves, i.e., phononlike collective excitations, in the hard‐Core Yukawa system. The upper limit of q for these collective modes is practically independent of the thermodynamic state. The computed transverse current correlation functions show that at liquid densities the hard‐Core Yukawa system is able to sustain shear wave propagation above a critical q; the upper limit of q for sound waves and the lower limit for shear waves nearly coincide. All of these features are qualitatively similar to those found for hard spheres. However, there are significant quantitative differences, which reflect the influence of the attractive Yuk...

  • Properties of a hard‐Core Fluid with a Yukawa tail studied by molecular dynamics and the mean spherical approximation
    The Journal of Chemical Physics, 1992
    Co-Authors: C. Rey, Luis J. Gallego, Luis E. Gonzalez
    Abstract:

    A molecular dynamics simulation method for computing the static and dynamic properties of a hard‐Core Fluid with a Yukawa tail is developed. The calculated static bulk properties show good agreement with the Monte Carlo results previously reported. We have also calculated the thermodynamic properties within the mean spherical approximation by the energy, compressibility, and virial routes; the ‘‘exact’’ data are most closely approximated by the energy route. The computed values of the self‐diffusion constant are compared with those corresponding to a hard‐sphere Fluid; the results are consistent with previous findings that the cohesive part of the intermolecular potential plays a significant role in reducing diffusion.