  If dark matter particles have an electric charge, as in models of
millicharged dark matter, such particles should be accelerated in the same
astrophysical accelerators that produce ordinary cosmic rays, and their spectra
should have a predictable rigidity dependence. Depending on the charge, the
resulting "dark cosmic rays" can be detected as muon-like or neutrino-like
events in Super-Kamiokande, IceCube, and other detectors. We present new limits
and propose several new analyses, in particular, for the Super-Kamiokande
experiment, which can probe a previously unexplored portion of the millicharged
dark matter parameter space. Most of our results are fairly general and apply
to a broad class of dark matter models.
