How strong is the invisible component of the magnetic field in the Earth's core

1993 ◽  
Vol 20 (19) ◽  
pp. 2083-2086 ◽  
Author(s):  
Keke Zhang ◽  
D. R. Fearn
Keyword(s):  
Magnetic Field ◽  
Earth’S Core ◽  
Earth's Core ◽  
The Magnetic Field ◽  
The Invisible

scholarly journals Approaching Earth’s core conditions in high-resolution geodynamo simulations

2019 ◽  
Vol 219 (Supplement_1) ◽  
pp. S137-S151 ◽  
Author(s):  
Julien Aubert
Keyword(s):  
Magnetic Field ◽  
High Resolution ◽  
Large Scale ◽  
Small Scale ◽  
Low Resolution ◽  
Earth’S Core ◽  
Earth's Core ◽  
Density Anomaly ◽  
Core Conditions ◽  
The Magnetic Field

SUMMARY The geodynamo features a broad separation between the large scale at which Earth’s magnetic field is sustained against ohmic dissipation and the small scales of the turbulent and electrically conducting underlying fluid flow in the outer core. Here, the properties of this scale separation are analysed using high-resolution numerical simulations that approach closer to Earth’s core conditions than earlier models. The new simulations are obtained by increasing the resolution and gradually relaxing the hyperdiffusive approximation of previously published low-resolution cases. This upsizing process does not perturb the previously obtained large-scale, leading-order quasi-geostrophic (QG) and first-order magneto-Archimedes-Coriolis (MAC) force balances. As a result, upsizing causes only weak transients typically lasting a fraction of a convective overturn time, thereby demonstrating the efficiency of this approach to reach extreme conditions at reduced computational cost. As Earth’s core conditions are approached in the upsized simulations, Ohmic losses dissipate up to 97 per cent of the injected convective power. Kinetic energy spectra feature a gradually broadening self-similar, power-law spectral range extending over more than a decade in length scale. In this range, the spectral energy density profile of vorticity is shown to be approximately flat between the large scale at which the magnetic field draws its energy from convection through the QG-MAC force balance and the small scale at which this energy is dissipated. The resulting velocity and density anomaly planforms in the physical space consist in large-scale columnar sheets and plumes, respectively, co-existing with small-scale vorticity filaments and density anomaly ramifications. In contrast, magnetic field planforms keep their large-scale structure after upsizing. The small-scale vorticity filaments are aligned with the large-scale magnetic field lines, thereby minimizing the dynamical influence of the Lorentz force. The diagnostic outputs of the upsized simulations are more consistent with the asymptotic QG-MAC theory than those of the low-resolution cases that they originate from, but still feature small residual deviations that may call for further theoretical refinements to account for the structuring constraints of the magnetic field on the flow.

Torsional oscillations and the magnetic field within the Earth's core

Nature ◽  
10.1038/41987 ◽  
1997 ◽  
Vol 388 (6644) ◽  
pp. 760-763 ◽  
Author(s):  
Stephen Zatman ◽  
Jeremy Bloxham
Keyword(s):  
Magnetic Field ◽  
Earth’S Core ◽  
Torsional Oscillations ◽  
Earth's Core ◽  
The Magnetic Field

scholarly journals Changing the Location of the Earth's Core, the main Force operating that Changes the Magnetic Field of the Earths

2020 ◽  
pp. 125-127
Keyword(s):  
Magnetic Field ◽  
Earth’S Core ◽  
Earth's Core ◽  
The Core ◽  
The Earth ◽  
North And South ◽  
The Magnetic Field

The core of the earth has oscillations which are flexible, and which are affected by pressure that can change its every direction, particularly to that of the two poles. In its intermittent oscillations towards north and south, the core constitutes an additional factor in the earth’s equilibrium, and this phenomenon also causes alternating changes in the magnetic field towards north and south.

Fast (non-)diffusive Quasi-Geostrophic Magneto-Coriolis Modes in the Earth's core

2021 ◽  
Author(s):  
Felix Gerick ◽  
Dominique Jault ◽  
Jerome Noir
Keyword(s):  
Magnetic Field ◽  
Magnetic Energy ◽  
Three Dimensional ◽  
Outer Core ◽  
Equatorial Region ◽  
Earth’S Core ◽  
Earth's Core ◽  
Strong Focusing ◽  
Geomagnetic Observations ◽  
And Diffusion

<p> Fast changes of Earth's magnetic field could be explained by inviscid and diffusion-less quasi-geostrophic (QG) Magneto-Coriolis modes. We present a hybrid QG model with columnar flows and three-dimensional magnetic fields and find modes with periods of a few years at parameters relevant to Earth's core. These fast Magneto-Coriolis modes show strong focusing of their kinetic and magnetic energy in the equatorial region, while maintaining a relatively large spatial structure along the azimuthal direction. Their properties agree with some of the observations and inferred core flows. We find additionally, in contrast to what has been assumed previously, that these modes are not affected significantly by magnetic diffusion. The model opens a new way of inverting geomagnetic observations to the flow and magnetic field deep within the Earth's outer core.</p>

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