  Over a handful of rotation periods, dynamical processes in barred galaxies
induce non-axisymmetric structure in dark matter halos. Using n-body
simulations of a Milky Way-like barred galaxy, we identify both a trapped
dark-matter component, a shadow bar, and a strong response wake in the
dark-matter distribution that affects the predicted dark-matter detection rates
for current experiments. The presence of a baryonic disk together with
well-known dynamical processes (e.g. spiral structure and bar instabilities)
increase the dark matter density in the disk plane. We find that the magnitude
of the combined stellar and shadow bar evolution, when isolated from the effect
of the axisymmetric gravitational potential of the disk, accounts for >30% of
this overall increase in disk-plane density. This is significantly larger that
of previously claimed deviations from the standard halo model. The dark-matter
density and kinematic wakes driven by the Milky Way bar increase the
detectability of dark matter overall, especially for the experiments with
higher $v_{min}$. These astrophysical features increase the detection rate by
more than a factor of two when compared to the standard halo model and by a
factor of ten for experiments with high minimum recoil energy thresholds. These
same features increase (decrease) the annual modulation for low (high) minimum
recoil energy experiments. We present physical arguments for why these dynamics
are generic for barred galaxies such as the Milky Way rather than contingent on
a specific galaxy model.
