  QCD with two light quark flavors at high baryonic density and low temperature
is a color superconductor. The diquark condensate partially breaks the SU(3)
gauge symmetry down to an SU(2) subgroup. We study thermal fluctuations of the
superconductor for temperatures below the gap. These are described by a simple
transport equation, linked to a quasiparticle behavior of the thermal
excitations of the condensate. When solved in the collisionless limit and close
to equilibrium, it gives rise to the ``hard superconducting loop'' (HSL)
effective theory for the unbroken SU(2) gauge fields with momenta smaller than
the gap. This theory describes Debye screening and Landau damping of the gauge
fields in the presence of the diquark condensate. We also explain how our
effective theory follows to one-loop order from quantum field theory. Our
approach provides a convenient starting point for the computation of transport
coefficients of the two-flavor color superconductor.
