HR: 1340h
AN: SM53A-1086    [Abstracts]
TI: On the Boundary Between a Proto-star Magnetosphere and its Protoplanetary Disk
AU: * Kobayashi, Y
EM: ykobay@geo.titech.ac.jp
AF: Department of Earth and Planetary Sciences Tokyo Institute of Technology, 2-12-1 Ookayama, Meguro-ku, Tokyo, 152-8551, Japan
AU: Fujimoto, M
EM: fujimoto@stp.isas.jaxa.jp
AF: ISAS/JAXA, 3-1-1 Yoshinodai, Sagamihara, Kanagawa, 229-8510, Japan
AB: We have investigated how the Magneto Rotational Instability (hereafter MRI) affects the structure of the boundary between a proto-star magnetosphere and its proto-planetary disk. 3D resistive MHD simulations of MRI in a proto-planetary disk, especially near its inner-edge that separates the magnetic field dominated proto-starfs magnetosphere and the gas dominated disk, have been conducted. Cylindrical co-ordinates have been used while the vertical structure has been neglected (cylindrical disk approximation). In our 2D simulations on the radial-vertical plane, we modeled the inner-edge by giving a strong magnetic field on the magnetospheric side where the MRI cannot grow, and the disk part is threaded by a weak magnetic field which makes the region to be MRI unstable. In the disk, with the radial variation of the angular velocity that decreases with distance from the central star, the MRI grows faster in the inner region than in the outer part. Then the MRI becomes most active in the inner part of the disk, less in the outer part, and none in the magnetosphere. This situation is also achieved by considering a magnetic resistivity that increases with distance. Putting a magnetic resistivity in the outer region representing the gdead zoneh gives the same spatial profile of MRI activity. In these situations where MRI is confined to the inner-part of the disk, we have found that the profile of the angular velocity is strongly changed to have a discontinuous jump at the inner-edge, which is both large and sharp enough to destabilize the Kelvin- Helmholtz Instability in r-phi plane. These results suggest that the disk inner-edge is heavily perturbed by the MRI and possibly by the secondarily induced KHI.
DE: 0560 Numerical solutions (4255)
DE: 2700 MAGNETOSPHERIC PHYSICS (6939)
DE: 6050 Plasma and MHD instabilities (2149, 2752, 7836)
SC: SPA-Magnetospheric Physics [SM]
MN: 2007 Fall Meeting