Forces on a small diamagnetic sphere in an AC/DC field

["nortonsm" <nortonsm@xxxxxxxxx>]

I'm trying to work out the forces experienced by a very small
diamagnetic metallic sphere in a nonuniform magnetic field. In one
case the magnetic field is DC, in the other AC. Now what I do know
(which might not be much!):

1) the small (micron size range) particle should have complete field
penetration at the frequencies of interest

2) A static magnetic non-uniform field (like that above a current
ring) will suspend a diamagnetic particle (Diagmagnetic Suspension:
"Magnetic Fields" Knoepfel, H.E.John Wiley and Sons, 2000)

3) An AC field will induce oscillating currents in the particle. Due
to its small size and moderate frequencies, the quasistatic limit
should hold. These induced "eddy currents" will generate an induced
magnetic field which should change the forces on the suspended
particle.

My question: I'm more interested in the AC case since as referenced
above, the DC case is covered in Knoepfel's book. What will be the
result in terms of forces of an AC magnetic field on the suspension 
of the particle? How do I go about doing this calculation? 
Basically,what I don't know is what limitations or "simplifications" 
I can do when dealing with VERY small metal diamagnetic particles? 
Are the induced eddy currents significant at all in particles with 
such small size?

I'm currently demo'ing Femlab to model this problem. This problem 
obviously has azimuthal symmetry if one imagines a diamagnetic 
sphere hovering above the center of a coil. I understand how to 
model the coil, but Im not sure how to specify the boundary 
conditions on the diamagnetic sphere (say its made of silver). Some 
choices I have on boundary conditions include: 
1) Electric insulation/continuity: n(dot)J=0, n(curl)H=0
or 
2) Magnetic discontinuity: n(curl)H1=n(curl)H2

Any thoughts or references would be appreciated. Thanks!!!

-Scott