  The adiabatic invariance of the magnetic moment during particle motion is of
fundamental importance to the dynamics of magnetized plasma. The related rate
of pitch angle scattering is investigated here for fast particles that
thermally stream through static magnetic perturbations. For a uniform magnetic
field with a localized perturbation it is found that the curvature parameter
$\kappa^2=\min(R_c/\rho_L)$ does not predict the level of pitch angle
scattering. Instead, based on numerical integration of particle orbits in
prescribed magnetic fields, we derive predictions for the particle scattering
rates, which can be characterized by the relative perturbation amplitude
$A\simeq \delta B/B$, and the particle Larmor radius normalized by the
field-aligned wavelength of the perturbations, $\rho_L/\lambda_{\|}$. Particles
with $\rho_L/\lambda_{\|}\simeq1$, are subject to strong pitch angle
scattering, while the level of scattering vanishes for both the limits of
$\rho_L/\lambda_{\|} \ll 1$ and $\rho_L/\lambda_{\|} \gg 1$. The results are
summarized in terms of a scattering operator, suitable for including the
described scattering in basic kinetic models.
