Journal: Geophysical and Astrophysical Fluid Dynamics

Abbreviation

Geophys. Astrophys. Fluid Dyn.

Publisher

Taylor & Francis

Journal Volumes

ISSN

0309-1929
1029-0419

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Publications 1 - 7 of 7
  • Differential rotation in giant planets maintained by density-stratified turbulent convection
    Item type: Journal Article
    Glatzmaier, Gary A.; Evonuk, Martha; Rogers, Tamara M. (2009)
    Geophysical and Astrophysical Fluid Dynamics
  • Libration-driven inertial waves and mean zonal flows in spherical shells
    Item type: Journal Article
    Lin, Yufeng; Noir, Jérôme André Roland (2021)
    Geophysical and Astrophysical Fluid Dynamics
    Several planetary bodies in our solar system undergo a forced libration owing to gravitational interactions with their orbital companions, leading to complex fluid motions in their metallic liquid cores or subsurface oceans. In this study, we numerically investigate flows in longitudinally librating spherical shells. We focus on the Ekman number dependencies of several shear layers when the libration frequency is less than twice of the rotation frequency and the libration amplitude is small. Time-dependent flows mainly consist of inertial waves excited at the critical latitudes due to the Ekman pumping singularities, forming conical shear layers. In particular, previous theoretical studies have proposed different scalings for the conical shear layers spawned from the critical latitudes at the inner boundary. Our numerical results favour the velocity amplitude scaling (Formula presented.) predicted by Le Dizès & Le Bars (J. Fluid Mech. 2017, 826, 653) over the scaling (Formula presented.) initially proposed by Kerswell (J. Fluid Mech. 1995, 298, 311), though the Ekman numbers in our calculations are not sufficiently small to pin down this scaling. Non-linear interactions in the boundary layers drive a mean zonal flow with several geostrophic shears. Our numerical results show that geostrophic shears associated with the critical latitudes at the inner and outer boundaries exhibit the same scalings, i.e. an amplitude of (Formula presented.) over a width of (Formula presented.). Apart from the geostrophic shear associated with the critical latitude, our numerical results show that the reflection of inertial waves can induce a geostrophic shear with an amplitude of (Formula presented.) over a width of (Formula presented.). As the amplitude of the geostrophic shears increases as reducing the Ekman number, the geostrophic shears in the mean flows may be significant in planetary cores and subsurface oceans given small Ekman numbers of these systems.
  • Introduction
    Item type: Journal Article
    Ferriz-Mas, A.; Hollerbach, R.; Stefani, F.; et al. (2013)
    Geophysical and Astrophysical Fluid Dynamics
  • Magnetohydrodynamic simulations of the elliptical instability in triaxial ellipsoids
    Item type: Journal Article
    Cébron, D.; Le Bars, M.; Maubert, P.; et al. (2012)
    Geophysical and Astrophysical Fluid Dynamics
  • The inherent instability of axisymmetric magnetostrophic dynamo models
    Item type: Journal Article
    Hardy, Colin; Livermore, Philip W.; Niesen, Jitse (2022)
    Geophysical and Astrophysical Fluid Dynamics
    Recent studies have demonstrated the possibility of constructing magnetostrophic dynamo models, which describe the slowly evolving background state of Earth's magnetic field when inertia and viscosity are negligible. Here we explore the properties of steady, stable magnetostrophic states as a leading order approximation to the slow dynamics within Earth's core. For the case of an axisymmetric magnetostrophic system driven by a prescribed alpha-effect, we confirmed the existence of four known steady states: +/- B-d, +/- B-q, where B(d )is purely dipolar and Bq is purely quadrupolar. Importantly, here we show that in all but the most weakly driven cases, an initial magnetic field that is not purely dipolar or quadrapolar never converges to these states. Despite this instability, we also show that there are a plethora of instantaneous solutions that are quasi-steady, but nevertheless unstable. If the dynamics in Earth's core are reasonably modelled by a strongly driven alpha-effect, this work suggests that the background state can never be steady. We discuss the difficulties in comparing our magnetostrophic models with geomagnetic timeseries.
  • Kinematic dynamo action in spherical Couette flow
    Item type: Journal Article
    Wei, Xing; Jackson, Andrew; Hollerbach, Rainer (2012)
    Geophysical and Astrophysical Fluid Dynamics
  • Fractured porous media, by P. M. Adler, J.-F. Thovert and V. V. Mourzenko
    Item type: Book Review
    Herrmann, Hans Jürgen (2013)
    Geophysical and Astrophysical Fluid Dynamics
Publications 1 - 7 of 7