Net force on a Halbach Array in a uniform magnetic field

[Arshavsky]

I have been unable to determine whether a Halbach Array of permanent magnets would experience a net force in a uniform magnetic field.

 

[mfb]

Without motion, the only thing that experiences a net force in a uniform magnetic field would be magnetic monopoles, and they haven't been observed (as free particles) yet.

 

[rumborak]

Is that true? How about the classic compass needle? It's a normal dipole and it experiences a rotational force in a (to a first degree) uniform field.

 

[mfb]

It is only torque, it is not a net force (that would accelerate the center of mass).