Liquid sodium models of the Earth’s core

Abstract

Our understanding of the dynamics of the Earth's core can be advanced by a combination of observation, experiments, and simulations. A crucial aspect of the core is the interplay between the flow of the conducting liquid and the magnetic field this flow sustains via dynamo action. This non-linear interaction, and the presence of turbulence in the flow, precludes direct numerical simulation of the system with realistic turbulence. Thus, in addition to simulations and observations (both seismological and geomagnetic), experiments can contribute insight into the core dynamics. Liquid sodium laboratory experiments can serve as models of the Earth's core with the key ingredients of conducting fluid, turbulent flow, and overall rotation, and can also approximate the geometry of the core. By accessing regions of parameter space inaccessible to numerical studies, experiments can benchmark simulations and reveal phenomena relevant to the Earth's core and other planetary cores. This review focuses on the particular contribution of liquid sodium spherical Couette devices to this subject matter.

On the inverse cascade and flow speed scaling behaviour in rapidly rotating Rayleigh–Bénard convection

“…Vorobieff & Ecke 2002;King et al 2009;Kunnen, Geurts & Clercx 2010;Ecke & Niemela 2014;Stellmach et al 2014) and, much like natural systems, can access a wide range of Pr values. Liquid metals (Pr ≈ 0.025) (Aurnou & Olson 2001;Aubert et al 2001;King & Aurnou 2013;Zimmerman et al 2014;Adams et al 2015;Aurnou et al 2018;Vogt et al 2018), water (Pr ≈ 7) (Sumita & Olson 2002;Vorobieff & Ecke 2002;King et al 2009;Cheng et al 2015) and gases (Pr ≈ 1) (Niemela, Babuin & Sreenivasan 2010;Ecke & Niemela 2014) have all been utilised. As for numerical calculations, fluids with smaller values of Pr reach higher values of Re than higher Pr fluids for equivalent Ra.…”

Continuous data assimilation for the magnetohydrodynamic equations in 2D using one component of the velocity and magnetic fields

“…Therefore the techniques of data assimilation, which were developed in weather prediction, have been applied to the MHD equations in recent years (see, e.g., [BRB02, CRB07, FEA07, FHJ + 10, GDZGP00, LJL14, MDMB06, SML16, STK07, TRT + 08]). It has also been speculated in [ASZL15] that data assimilation for magnetohydrodynamics may be useful in liquid sodium experiments modeling the Earth's core.…”

The nature of mean-field generation in three classes of optimal dynamos

“…There is only a small number of successful experimental dynamos to date (Gailitis et al 2000;Stieglitz & Müller 2001;Monchaux et al 2007). Several other dynamo experiments are currently in operation; see the review by Adams et al (2015), who also discuss the newer Madison dynamo experiment and the Derviche-Tourneur sodium experiment. They all work with liquid sodium, and they all involve flows with significant swirl -in anticipation that those types of dynamos would be most suitable for driving dynamo action most easily.…”