Making Stellar Magnetic Fields in a Jar

An experiment at the University of Maryland reports the first experimental observation of a magnetorotational instability---essentially the creation of an induced magnetic field amid the turbulence of a rotating electrically conducting fluid immersed in a separate magnetic field.

In the Maryland experiment a baseball-sized copper ball is rotated within a vessel containing liquid sodium. With this setup, the researchers try to simulate the ingredients shared in common by Earth's core, the outer envelopes of stars, and the accretion disk surrounding black holes.In each case a conducting fluid, differential rotation (inner parts of the fluid rotating faster than outer parts), and potent magnetism add up to interesting physics. Until now there had been only theories and simulations of this physical environment.

Now, the Maryland experiment actually demonstrates that an organized magnetic field (see figures at Maryland website) can arise even from a hydrodynamic turbulent fluid. According to Daniel Lathrop, one of the scientists involved, the new test allows researchers to study the interplay between moving fluids, the ways in which turbulence can occur, and how the fluid rotation can be braked. (Sisan et al., Physical Review Letters, 10 September; contact Lathrop at dpl@complex.umd.edu, 301-405-1594)