  The CoGeNT collaboration has recently published results from a fifteen month
data set which indicate an annual modulation in the event rate similar to what
is expected from weakly interacting massive particle interactions. It has been
suggested that the CoGeNT modulation may actually be caused by other annually
modulating phenomena, specifically the flux of atmospheric muons underground or
the radon level in the laboratory. We have compared the phase of the CoGeNT
data modulation to that of the concurrent atmospheric muon and radon data
collected by the MINOS experiment which occupies an adjacent experimental hall
in the Soudan Underground Laboratory. The results presented are obtained by
performing a shape-free $\chi^{2}$ data-to-data comparison and from a
simultaneous fit of the MINOS and CoGeNT data to phase-shifted sinusoidal
functions. Both tests indicate that the phase of the CoGeNT modulation is
inconsistent with the phases of the MINOS muon and radon modulations at the
\unit[3.0]{$\sigma$} level.
