  During the final growth phase of giant planets, accretion is thought to be
controlled by a surrounding circumplanetary disk. Current astrophysical
accretion disk models rely on hydromagnetic turbulence or gravitoturbulence as
the source of effective viscosity within the disk. However, the
magnetically-coupled accreting region in these models is so limited that the
disk may not support inflow at all radii, or at the required rate. Here, we
examine the conditions needed for self-consistent accretion, in which the disk
is susceptible to accretion driven by magnetic fields or gravitational
instability. We model the disk as a Shakura-Sunyaev $\alpha$ disk and calculate
the level of ionisation, the strength of coupling between the field and disk
using Ohmic, Hall and Ambipolar diffusevities for both an MRI and vertical
field, and the strength of gravitational instability. We find that the standard
constant-$\alpha$ disk is only coupled to the field by thermal ionisation
within $30\,R_J$ with strong magnetic diffusivity prohibiting accretion through
the bulk of the midplane. In light of the failure of the constant-$\alpha$ disk
to produce accretion consistent with its viscosity we drop the assumption of
constant-$\alpha$ and present an alternate model in which $\alpha$ varies
radially according to the level magnetic turbulence or gravitoturbulence. We
find that a vertical field may drive accretion across the entire disk, whereas
MRI can drive accretion out to $\sim200\,R_J$, beyond which Toomre's $Q=1$ and
gravitoturbulence dominates. The disks are relatively hot ($T\gtrsim800\,$K),
and consequently massive ($M_{\text{disk}}\sim0.5\,M_J$).
