Migration of Extrasolar Planets: Effects from X-Wind Accretion Disks

Abstract

Magnetic fields are dragged in from the interstellar medium during the gravitational collapse that forms star/disk systems. Consideration of mean field magnetohydrodynamics (MHD) in these disks shows that magnetic effects produce subkeplerian rotation curves and truncate the inner disk. This letter explores the ramifications of these predicted disk properties for the migration of extrasolar planets. Subkeplerian flow in gaseous disks drives a new migration mechanism for embedded planets and modifies the gap opening processes for larger planets. This subkeplerian migration mechanism dominates over Type I migration for sufficiently small planets (m_P < 1 M_\earth) and/or close orbits (r < 1 AU). Although the inclusion of subkeplerian torques shortens the total migration time by only a moderate amount, the mass accreted by migrating planetary cores is significantly reduced. Truncation of the inner disk edge (for typical system parameters) naturally explains final planetary orbits with periods P=4 days. Planets with shorter periods P=2 days can be explained by migration during FU-Ori outbursts, when the mass accretion rate is high and the disk edge moves inward. Finally, the midplane density is greatly increased at the inner truncation point of the disk (the X-point); this enhancement, in conjunction with continuing flow of gas and solids through the region, supports the in situ formation of giant planets.

15 pages, 2 figures, accepted to ApJ Letters

References in corpus (7)

• Halting Type I planet migration in non-isothermal disks
• On disc protoplanet interactions in a non-barotropic disc with thermal diffusion
• Mean-Field Magnetohydrodynamics of Accretion Disks
• Diffusive Migration of Low-Mass Proto-planets in Turbulent Disks
• General Analysis of Type I Planetary Migration with Stochastic Perturbations
• X-winds in Action
• The Challenge of Sub-Keplerian Rotation for Disk Winds

Cited by in corpus (10)

• The Role of Magnetic Fields in Protostellar Outflows and Star Formation
• The Fate of Scattered Planets
• Coupled evolutions of the stellar obliquity, orbital distance, and planet's radius due to the Ohmic dissipation induced in a diamagnetic hot Jupiter around a magnetic T Tauri star
• Migrating Planets into Ultra-Short-Period Orbits during Episodic Accretion Events
• Stability of Magnetized Disks and Implications for Planet Formation
• Vertical Structure of Magnetized Accretion Disks around Young Stars
• Disc-planet interactions in sub-keplerian discs
• Gravitational Collapse and Disk Formation in Magnetized Cores
• Accretion of Rocky Planets by Hot Jupiters
• Halting Migration in Magnetospherically Sculpted Protoplanetary Disks