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It is widely accepted that astrophysical magnetic fields are generated by dynamo action. In many cases these fields exhibit organisation on a scale larger than that of the underlying turbulent flow (e.g., the eleven-year solar cycle). The…

Fluid Dynamics · Physics 2018-12-03 Laura K. Currie , Steven M. Tobias

The near-bottom mixing that allows abyssal waters to upwell tilts isopycnals and spins up flow over the flanks of mid-ocean ridges. Meso- and large-scale currents along sloping topography are subjected to a delicate balance of Ekman arrest…

Atmospheric and Oceanic Physics · Physics 2022-04-13 Henry G. Peterson , Jörn Callies

It was recently argued that one-dimensional systems of several strongly interacting fermions of different mass undergo critical transitions between different spatial orderings when the external confinement adiabatically changes its shape.…

Quantum Gases · Physics 2021-11-22 Damian Włodzyński , Tomasz Sowiński

The possibility of fast dynamo action by collisionless kinetic Alfven Wave turbulence is demonstrated. The irreversibility necessary to lock in the generated field is provided by electron Landau damping, so the induced electric field does…

Astrophysics · Physics 2009-11-06 I. Gruzinov , A. Das , P. H. Diamond

Large-scale planetary or stellar magnetic fields generated by a dynamo effect are mostly attributed to flows forced by buoyancy forces in electrically conducting fluid layers. However, these large-scale fields may also be controlled by…

Solar and Stellar Astrophysics · Physics 2015-06-22 David Cébron , Rainer Hollerbach

We present a three--pronged numerical approach to the dynamo problem at low magnetic Prandtl numbers $P_M$. The difficulty of resolving a large range of scales is circumvented by combining Direct Numerical Simulations, a Lagrangian-averaged…

Geophysics · Physics 2009-11-10 Y. Ponty , P. D. Mininni , D. C. Montgomery , J. -F. Pinton , H. Politano , A. Pouquet

Hydromagnetic dynamo theory provides the prevailing theoretical description for the origin of magnetic fields in the universe. Here we consider the problem of kinematic, small-scale dynamo action driven by a random, incompressible,…

Plasma Physics · Physics 2011-03-10 Joanne Mason , Leonid Malyshkin , Stanislav Boldyrev , Fausto Cattaneo

Several solar-like stars exhibit cyclic magnetic activity similar to the Sun as found in photospheric and chromospheric emission. We want to understand the physical mechanism involved in rotational dependence of these activity cycle…

Solar and Stellar Astrophysics · Physics 2018-08-22 Jörn Warnecke

The Earth's magnetic field is generated by dynamo action driven by convection in the outer core. For numerical reasons, inertial and viscous forces play an important role in geodynamo models; however, the primary dynamical balance in the…

Earth and Planetary Astrophysics · Physics 2016-06-08 David W. Hughes , Fausto Cattaneo

The Feynman demonstration that electromagnetic field momentum is real-even for static fields-can be made more pedagogically useful by simplifying its geometry. Instead of Feynman's disk with charged balls on its surface, this article uses…

History and Philosophy of Physics · Physics 2023-10-23 Oliver Davis Johns

We numerically investigate the efficiency of a spherical Couette flow at generating a self-sustained magnetic field. No dynamo action occurs for axisymmetric flow while we always found a dynamo when non-axisymmetric hydrodynamical…

Geophysics · Physics 2020-07-17 Céline Guervilly , Philippe Cardin

It is numerically demonstrated by means of a magnetohydrodynamics code that a short Taylor-Couette setup with a body force can sustain dynamo action. The magnetic threshold is comparable to what is usually obtained in spherical geometries.…

Numerical Analysis · Mathematics 2015-06-04 C. Nore , J. -L. Guermond , R. Laguerre , J. Leorat , F. Luddens

We present a numerical study of dynamo action in a conducting fluid encased in a metallic spherical shell. Motions in the fluid are driven by differential rotation of the outer metallic shell, which we refer to as "the wall". The two…

Fluid Dynamics · Physics 2014-01-08 Celine Guervilly , Toby S. Wood , Nicholas H. Brummell

We solve the equations of motion of a one-dimensional planar Heisenberg (or Vaks-Larkin) model consisting of a system of interacting macro-spins aligned along a ring. Each spin has unit length and is described by its angle with respect to…

Earth and Planetary Astrophysics · Physics 2015-03-19 N. Mori , D. Schmitt , A. Ferriz-Mas , J. Wicht , H. Mouri , A. Nakamichi , M. Morikawa

We study dynamo action in a convective layer of electrically-conducting, compressible fluid, rotating about the vertical axis. At the upper and lower bounding surfaces, perfectly-conducting boundary conditions are adopted for the magnetic…

Solar and Stellar Astrophysics · Physics 2011-11-23 Benjamin F. N. Favier , Paul J. Bushby

We consider dynamo action driven by three-dimensional rotating anelastic convection in a spherical shell. Motivated by the behaviour of the solar dynamo, we examine the interaction of hydromagnetic modes with different symmetries and…

Solar and Stellar Astrophysics · Physics 2016-07-06 Raphaël Raynaud , Steven M. Tobias

A marginally excited cosmic kinematic dynamo is found in the background of a non-singular anisotropic Kasner cosmological metric solution of Einstein field equation of general relativity. The magnetic field is not amplified but is frozen…

Astrophysics · Physics 2007-07-10 L. C. Garcia de Andrade

The non-equilibrium spin dynamics of a one-dimensional system of repulsively interacting fermions is studied by means of density-matrix renormalization-group simulations. We focus on the short-time decay of the oscillation amplitudes of the…

Strongly Correlated Electrons · Physics 2012-06-20 Sebastiano Peotta , Davide Rossini , Pietro Silvi , G. Vignale , Rosario Fazio , Marco Polini

Rapidly rotating convection-driven dynamos are investigated under different kinematic and magnetic boundary conditions using DNS. At a fixed rotation rate, represented by the Ekman number $E=5\times10^{-7}$, the thermal forcing is varied…

Fluid Dynamics · Physics 2022-11-23 Souvik Naskar , Anikesh Pal

The dynamo equations are solved numerically with a helical forcing corresponding to the Roberts flow. In the fully turbulent regime the flow behaves as a Roberts flow on long time scales, plus turbulent fluctuations at short time scales.…

Fluid Dynamics · Physics 2020-04-24 Yannick Ponty , Franck Plunian