  The coherent manipulation of spin observables in storage rings provides
opportunities to test the application of some fundamental dynamical principles.
In this context, it is possible to confirm, using gauge invariance and Lorentz
invariance, a conjecture framed by A. M. Kondratenko concerning the "natural"
or "intrinsic" resonance strength applicable to a spin rotation from a
controlled Froissart-Stora sweep with an RF dipole magnet. The discussion
includes a brief treatment of the "forced" component of the resonance strength
associated with the effect of the betatron oscillations induced by the
operation of the RF diple and a discussion of the effective resonance strength
as a function of betatron tunes.
