  Non-axisymmetric stationary magnetic perturbations lead to the formation of
homoclinic tangles near the divertor magnetic saddle in tokamak discharges.
These tangles intersect the divertor plates in static helical structures that
delimit the regions reached by open magnetic field lines reaching the plasma
column and leading the charged particles to the strike surfaces by parallel
transport. In this article we introduce a non-axisymmetric rotating magnetic
perturbation to model the time development of the three-dimensional magnetic
field of a single-null DIII-D tokamak discharge developing a rotating tearing
mode. The stable and unstable manifolds of the asymmetric magnetic saddle are
calculated through an adaptive method providing the manifold cuts at a given
poloidal plane and the strike surfaces. For the modeled shot, the experimental
heat pattern and its time development are well described by the rotating
unstable manifold, indicating the emergence of homoclinic lobes in a rotating
frame due to the plasma instabilities. In the model it is assumed that the
magnetic field is created by a stationary axisymmetric plasma current and a set
of rotating internal helical filamentary currents. The currents in the
filaments are adjusted to match the waveforms of the magnetic probes at the
mid-plane and the rotating magnetic field is introduced as a perturbation to
the axisymmetric field obtained from a Grad-Shafranov equilibrium
reconstruction code.
