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Recent observation has found tens of ring-gap substructures in the circum-stellar disk, where planets form. Some of the gap structures are expected to open via planet gravitational torque and are used to characterize unseen planets. However, most previous works have almost exclusively assumed the viscous disk. The origin of viscosity was widely accepted as Magneto-Rotational Instability (MRI). However, recent theoretical works have pointed out that MRI turbulence works only near the central star because of the low ionization fraction at the outer disk. The magnetized disk wind governs the disk evolution rather than the MRI turbulent viscosity at such an outer disk. Since most substructures are observed at the outer disk, the planet-disk interaction and the resulting gap formation need to be studied in the windy disk rather than the viscous disk.
Therefore, we conduct 3D global non-ideal magnetohydrodynamic (MHD) simulations of type-II planet-disk interaction that properly resolves the MRI turbulence and accommodates the MHD disk wind.
We found that the planet triggers the poloidal magnetic flux concentration around its orbit, likely associated with spiral density shocks. The concentrated magnetic flux strongly enhances angular momentum removal in the gap region. It alters the torque balance, making the planet-induced gap shape more similar to an inviscid disk while being much deeper. The gap region is characterized by a fast trans-sonic accretion flow asymmetric in azimuth about the planet and lacks the horseshoe turns. The formation of a magnetized circumplanetary disk will also be discussed.
Yuhiko Aoyama has been a Boya fellow postdoctoral researcher at the Kavli Institute of Astronomy and Astrophysics (KIAA) at Peking University since 2022. He received his Ph.D. from the University of Tokyo in Japan and was a Suimu fellow at Tsinghua University. His research interest is in the planet formation, particularly the formation of giant planets. He mainly works on the theoretical modeling of observable signatures of newly forming planets.