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Understanding Earth's Magnetic Field
neutron_p writes "Researchers from the University of Maryland's nonlinear dynamics and chaos research group are seeking to solve a major scientific mystery: How is the Earth's magnetic field formed and what causes changes in the field? To find answers, they are recreating on a small scale the forces that produce Earth's own magnetic field. Scientists have constructed a series of "geodynamos" - metal spheres filled with liquid sodium that emulate conditions of the Earth's spinning, churning molten iron core. This project involves more than 14 tons of sodium metal and a 10-foot stainless steel sphere."
I just so happen to be taking a Geology course, this semester. As I understand it, while Geologists are rather certain that radioactive materials provide the majority of the Earth's internal heat, they are equally certain that the core consists mostly of iron. The "liquid" outer sphere of iron produces the magnetic field through its motion.
As for the study itself: Wouldn't the Earth's own magnetic field interfere with the experiment, somehow? I saw nothing about this in the article, but I'm assuming that the Earth's magnetic field would either fail to significantly effect the results or the scientists are countering for it somehow, either in the experiment itself or in their calculations.
At any rate, I wish them the best of luck.
~UP
Eat the Path.
I don't see how measuring the effects on a 10-foot diameter sphere (filled with Na) can be equivalent to the effects on the central core of a 6400km-radius ball of rock (filled with many different elements). If they want to figure out more about the Earth's magnetic field, I suggest they take measurements, etc... on the EARTH.
The nice thing about building our own sphere of molten metal is that we a) know its structure and composition in detail, b) can put sensors inside, and c) can alter parameters (temperature gradient, rate of spin) and see what happens. None of these are practical for Earth, though we do have a reasonably good idea of what its composition and large-scale internal structure are.
The patterns of motion they're setting up are common to a very wide range of fluid systems - you don't need something as big as Earth to generate them. It's very hard to measure fluid flows and magnetic fields deep within the earth (all that's easy is density change boundaries), and the Earth's field isn't likely to flip within our lifetimes (or the next several centuries, minimum, even if the wierdness we're seeing _does_ represent the start of a flip). A small-scale mock-up run in the same turbulence modes that the core has will flip many times during the course of observation, and tell us a _lot_ about how the flipping occurs.
In short, we'll learn a lot more about the geomagnetic field from this experiment than we would from more studies of the Earth itself.