Models of planet-disk interaction are mainly based on two and three dimensional viscous hydrodynamical simulations. In such models, accretion is classically prescribed by an alpha parameter which characterizes the turbulent radial transport of angular momentum in the disk. This accretion scenario has been questioned for a few years and an alternative paradigm has been proposed that involves the vertical transport of angular momentum by magneto-hydrodynamical (MHD) winds.
We revisit planet-disk interaction in the context of MHD wind-launching protoplanetary disks. In particular, we focus on the planet’s ability to open a gap as well as the coupling between accretion, magnetic field and wind torque in the gap.
We carry out high-resolution 3D global non-ideal MHD simulations of a gaseous disk threaded by a large-scale vertical magnetic field harboring a planet in a fixed circular orbit using the GPU-accelerated code Idefix. We focus here on massive planets in highly-magnetized disks.
We find that gap-opening occurs, with deeper gaps when the planet mass increases and when the initial magnetization decreases. A planet gap is a privileged region for the accumulation of large-scale magnetic field, preferentially at the gap center or at the gap edges for some cases. This results in a fast accretion stream through the gap, which can become sonic at high magnetizations. The torque due to the MHD wind responds to the planet torque in a way that leads to an apparent more intense wind in the outer gap compared to the inner gap. This induces an asymmetric gap, both in depth and in width, that progressively erodes the outer gap edge, reducing the outer Lindblad torque and potentially reversing the migration direction of Jovian planets in magnetized disks. The complexity of the interplay between planet torque, wind torque and magnetic field transport makes predictions from phenomenological models hazardous.