The effects of viscosity on the circumplanetary disks residing in the
vicinity of protoplanets are investigated through two-dimensional
hydrodynamical simulations with the shearing sheet model. We find that
viscosity can affect properties of the circumplanetary disk considerably when
the mass of the protoplanet is Mpββ²33Mββ, where Mββ is
the Earth mass. However, effects of viscosity on the circumplanetary disk are
negligibly small when the mass of the protoplanet Mpββ³33Mββ. We
find that when Mpββ²33Mββ, viscosity can disrupt the spiral
structure of the gas around the planet considerably and make the gas smoothly
distributed, which makes the torques exerted on the protoplanet weaker. Thus,
viscosity can make the migration speed of a protoplanet lower. After including
viscosity, size of the circumplanetary disk can be decreased by a factor of
β³20. Viscosity helps to transport gas into the circumplanetary disk
from the differentially rotating circumstellar disk. The mass of the
circumplanetary disk can be increased by a factor of 50% after viscosity is
taken into account when Mpββ²33Mββ. Effects of viscosity on the
formation of planets and satellites are briefly discussed.Comment: 17 pages, 8 figures; accepted by RA