  Mirror and more generic hidden sector dark matter models can simultaneously
explain the DAMA, CoGeNT and CRESST dark matter signals consistently with the
null results of the other experiments. This type of dark matter can be captured
by the Earth and shield detectors because it is self-interacting. This effect
will lead to a diurnal modulation in dark matter detectors. We estimate the
size of this effect for dark matter detectors in various locations. For a
detector located in the northern hemisphere, this effect is expected to peak in
April and can be detected for optimistic parameter choices. The diurnal
variation is expected to be much larger for detectors located in the southern
hemisphere. In particular, if the CoGeNT detector were moved to e.g. Sierra
Grande, Argentina then a $5 \sigma$ dark matter discovery would be possible in
around 30 days of operation.
