  Dark matter in the form of particles from a hidden mirror sector has recently
been proposed as an explanation for the DAMA annual modulation signal. Here one
assumes that there exists a small mixing between photons and mirror photons. We
show that dark matter with this property can also be detected in
electromagnetic field penetration experiments. Such experiments can be used to
measure the speed and direction of the dark matter halo wind, the local
density, the temperature, and the strength of the photon-mirror photon mixing
interaction. An additional result would be a significant improvement of the
upper limit on the photon mass.
