Migration of Jupiter mass planets in low viscosity discs

Abstract

Type-II migration of giant planets has a speed proportional to the disc's viscosity for values of the alpha viscosity parameter larger than 1.e-4 . At lower viscosities previous studies, based on 2D simulations have shown that migration can be very chaotic and often characterized by phases of fast migration. The reason is that in low-viscosity discs vortices appear due to the Rossby-wave instability at the edges of the gap opened by the planet. Migration is then determined by vortex-planet interactions. Our aim is to study migration in low viscosity 3D discs. We performed numerical simulations using 2D (including self-gravity) and 3D codes. After selecting disc masses for which self-gravity is not important, 3D simulations without self-gravity can be safely used. In our nominal simulation only numerical viscosity is present. We then performed simulations with prescribed viscosity to assess the threshold below which the new migration processes appear. We show that for alpha viscosity <= 1.e-5 two migration modes are possible which differ from classical Type-II migration, in the sense that they are not proportional to the disc's viscosity. The first occurs when the gap opened by the planet is not very deep. This occurs in 3D simulations and/or when a big vortex forms at the outer edge of the planetary gap, diffusing material into the gap. We call this type of migration "vortex-driven migration". This migration is very slow and cannot continue indefinitely, because eventually the vortex dissolves. The second migration mode occurs when the gap is deep so that the planet's eccentricity grows to a value ~0.2 due to inefficient eccentricity damping by corotation resonances. This second, faster migration mode appears to be typical of 2D models in discs with slower damping of temperature's perturbations.

18 pages, 13 figures

References in corpus (17)

• Dynamical Outcomes of Planet-Planet Scattering
• The Occurrence and Mass Distribution of Close-in Super-Earths, Neptunes, and Jupiters
• Origins of Eccentric Extrasolar Planets: Testing the Planet-Planet Scattering Model
• A comparative study of disc-planet interaction
• Global simulations of protoplanetary disks with ohmic resistivity and ambipolar diffusion
• Planetesimal formation starts at the snow line
• Hints for a Turnover at the Snow Line in the Giant Planet Occurrence Rate
• On the formation of planetary systems via oligarchic growth in thermally evolving viscous discs
• The Migration of Gap-Opening Planets is not Locked to Viscous Disk Evolution
• Migration of massive planets in accreting disks
• Type I planetary migration in a self-gravitating disk
• Formation of a disc gap induced by a planet: Effect of the deviation from Keplerian disc rotation
• Vertical shear instability in accretion disc models with radiation transport
• Magnetocentrifugally Driven Flows from Young Stars and Disks. VI. Accretion with a Multipole Stellar Field
• Slowly-growing gap-opening planets trigger weaker vortices
• Planetary Torque in 3D Isentropic Disks
• Constraining the masses of planets in protoplanetary discs from the presence or absence of vortices -- Comparison with ALMA observations