Theory has it that magnetic fields tend to arise spontaneously in any rotating, electrically conducting fluid, explains Forest, whether that fluid is the molten iron in the Earth’s deep interior or the multi-million-degree plasma at the center of the Sun. But empirical evidence is much harder to come by, given that no one has yet figured out how to stick a probe into the core of the Earth, or into the heart of a star.
Thus the gaps. Says Forest, “How fast do the naturally occurring magnetic fields grow? When do they stop growing? What causes them to stop growing? That’s the big one. These are really, really fundamental questions that theory doesn’t address.”
And thus the Madison Dynamo Experiment. When the experiment is in operation, two opposing propellers stir the molten sodium in ways that approximate the flow of molten iron inside the Earth.
“At the core of the Earth, it is thought that there are lots of little flows and swirls occurring that contribute to the generation of the planet’s magnetic field,” says Forest. But “it’s the details that are important, and with the Madison Dynamo Experiment we can turn the knobs and see what happens.”
Indeed, says Forest, with the Madison Dynamo Experiment now operational and generating data, the secrets of how natural dynamos perform will begin to emerge and the limits of current theory can begin to be tested.
Text for this article comes from a NSF press releease.