  We study vortex domain wall dynamics in wide Permalloy strips driven by
applied magnetic fields and spin-polarized electric currents. As recently
reported [V. Est\'evez and L. Laurson, Phys. Rev. B, 93, 064403 (2016)], for
sufficiently wide strips and above a threshold field, periodic dynamics of the
vortex core are localized in the vicinity of one of the strip edges, and the
velocity drop typically observed for narrow strips is replaced by a
high-velocity plateau. Here, we analyze this behavior in more detail by means
of micromagnetic simulations. We show that the high-velocity plateau originates
from a repeated double switching of the magnetic vortex core, underlying the
periodic vortex core dynamics in the vicinity of the strip edge, i.e., the
"attraction-repulsion" effect. We also discuss the corresponding dynamics
driven by spin-polarized currents, as well as the effect of including quenched
random structural disorder to the system.
