Yuri I. Fujii¹, Satoshi Okuzumi^1,2, Takayuki Tanigawa³ and Shu-ichiro Inutsuka¹

¹Department of Physics, Nagoya University, Furo-cho, Chikusa-ku, Nagoya, Aichi 464-8602, Japan
²Department of Earth and Planetary Sciences, Tokyo Institute of Technology, Meguro-ku, Tokyo 152-8551, Japan
³Institute of Low Temperature Science, Hokkaido University, Sapporo 066-0819, Japan

We examine whether the magnetorotational instability (MRI) can serve as a mechanism of angular momentum transport in circumplanetary disks. For the MRI to operate the ionization degree must be sufficiently high and the magnetic pressure must be sufficiently lower than the gas pressure. We calculate the spatial distribution of the ionization degree and search for the MRI-active region where the two criteria are met. We find that there can be thin active layers at the disk surface depending on the model parameters, however, we find hardly any region which can sustain well-developed MRI turbulence; when the magnetic field is enhanced by MRI turbulence at the disk surface layer, a magnetically dominated atmosphere encroaches on a lower altitude and a region of well-developed MRI turbulence becomes smaller. We conclude that if there are no angular momentum transfer mechanisms other than MRI in gravitationally stable circumplanetary disks, gas is likely to pile up until disks become gravitationally unstable, and massive disks may survive for a long time.

Reference
Fujii YI, Okuzumi S, Tanigawa T and Shu-ichiro Inutsuka S-I (2014) On the Viability of the Magnetorotational Instability in Circumplanetary Disks. The Astrophysical Journal 785:101.
[doi:10.1088/0004-637X/785/2/101]

Link to Article