Protostars and Planets VI, Heidelberg, July 15-20, 2013
EXPOSING THE LONG LIVES OF SATELLITE FORMING DISKS
Fujii, Yuri (Nagoya University)
Okuzumi, Satoshi (Tokyo Institute of Thechnology)
Tanigawa, Takayuki (Hokkaido University)
Inutsuka, Shu-ichiro (Nagoya University)
Gaseous disks formed around newborn giant planets are called circumplanetary disks. These disks play important roles in supplying masses to gas giants and forming satellites. Since satellites are supposed to be formed in circumplanetary disks, the understanding of the disk property is crucial for satellite formation theories. The surface density changes according to the balance of gas supply from protoplanetary disks and gas accretion toward central planet. The former has recently analyzed through 3D hydrodynamical simulations. In this paper, we focus on the viscous evolution of circumplanetary disks. At present, the most promising mechanism of angular momentum transport in accretion disks is the magnetic turbulence which is driven by magnetorotational instability (MRI). For a disk to be MRI-active, gas in the disk should be ionized sufficiently. Thus, to investigate the MRI activity we have calculated the ionization degree in circumplanetary disks. As a result, we have found that circumplanetary disks are mostly MRI-inactive. Unless some other mechanisms promote the mass accretion, the lifetimes of circumplanetary disks are longer than previously thought, and possibly longer than the lifetimes of hparentalh protoplanetary disks. In this case, we have more chance to observe circumplanetary diks. In order to find out if this is the case, we need to investigate other possible mechanisms of mass accretion such as spiral density waves.
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