Laboratory simulation of the Earth's magnetic field

Question

I remember reading an article where a scientist was able to make a spinning iron tube with liquid nickel inside and it created a magnetic field, providing a laboratory-scale simulation of the generation of the Earth's magnetic field by convection in the outer core. I can't find any reference to this work on the web. I would like to find documents about such projects and see whether there have been any updates on the research.

Answer 1

Magnetohydrodynamic experiments intended to create laboratory analogues for the Earth's magnetic field generally use molten sodium rather than nickel. You can read about the details of one such project, DRESDYN, in this arXiv preprint.

The central part of the envisioned precession dynamo experiment… will be a cylindrical vessel of approximately 2 m diameter and length, rotating with up to 10 Hz around its symmetry axis, and with up to 1 Hz around another axis whose angle to the first axis can be varied between 90° and 45°. The inner cylindrical shell (made of copper) is immersed into a larger cylindrical stainless container with conical end parts that can later also be used to house alternative inner shells, e.g. in the form of ellipsoids.

The mechanical and safety demands for such a large scale sodium experiment are tremendous. With a total mass of approximately 20 tons (including the sodium in the conical end parts and the stainless steel walls) the sodium filled cylinder will have a moment of inertia of around 104 kg m². With a rotation rate of 10 Hz and a precession rate of 1 Hz, this amounts to a gyroscopic moment of 5 × 10⁶ Nm which requires an extremely massive basement and a careful avoidance of resonances. Further, the experiment must be fenced by a containment which can be quickly flooded with Argon in case of a sodium accident.

Exciting stuff! Here's the project website. According to a presentation at EGU this year, the building is currently under construction.

A group at the University of Maryland is conducting similar research, and has already constructed some experimental sodium dynamos.

I'm not aware of any such experiments involving nickel. Despite its high reactivity, sodium is easier to use for such experiments because of its much lower melting point and density. Nickel's melting point (1455°C) is only 83° below that of iron, so liquid nickel in an iron shell would be a tricky proposition.