  We investigate the effects of viscosity on disk-planet interaction and
discuss how type I migration of planets is modified. We have performed a linear
calculation using shearing-sheet approximation and obtained the detailed, high
resolution density structure around the planet embedded in a viscous disk with
a wide range of viscous coefficients. We use a time-dependent formalism that is
useful in investigating the effects of various physical processes on
disk-planet interaction. We find that the density structure in the vicinity of
the planet is modified and the main contribution to the torque comes from this
region, in contrast to inviscid case. Although it is not possible to derive
total torque acting on the planet within the shearing-sheet approximation, the
one-sided torque can be very different from the inviscid case, depending on the
Reynolds number. This effect has been neglected so far but our results indicate
that the interaction between a viscous disk and a planet can be qualitatively
different from an inviscid case and the details of the density structure in the
vicinity of the planet is critically important.
