Date: Fri, 26 Sep 2003 16:56:48 -0400
From: Daniel Perry Lathrop <dpl@complex.umd.edu>
To: Axel Brandenburg <brandenb@nordita.dk>
Subject: Re: MRI-MHD experiments

Dear Axel,

I've just e-mailed both of them.  There is one tiff image and one
larger (3.5 Mb) movie at http://complex.umd.edu/~dpl/mri
That is the simplest state, more complicated states exist at
higher applied field.

The experimental background state probably does not have z
invariance, unlike their paper.  I still think this should
preclude axisymmetric bifurcations, but not continuous axisymmetric
changes with parameter.

Yes, it seems the low Pm case is still to be done.  Our system:

Concentric spheres.
radius ratio 1/3.  Inner radius 0.05 m, outer radius 0.15 m
inner sphere copper (0.04 m^2/s mag. diff.)
sodium at 110 deg C (0.089 m^2/s mag. diff.)
Axial field strength 0 to .2 T
Rotation rates 2.5 to 40 RPS
Pm ~ 10^-5
Density of sodium 930 kg/m^3.

The primary bifurcation seems to a m=1 rotating pattern, at about
v_A l/eta = 1.

yours
dpl