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 email@example.com, 301-405-1594)