  It is shown that small externally applied magnetic perturbations can
significantly alter important geometric properties of magnetic flux surfaces in
tokamaks. Through 3D shaping, experimentally relevant perturbation levels are
large enough to influence turbulent transport and MHD stability in the pedestal
region. It is shown that the dominant pitch-resonant flux surface deformations
are primarily induced by non-resonant 3D fields, particularly in the presence
of significant axisymmetric shaping. The spectral content of the applied 3D
field can be used to control these effects.
