Formation of terrestrial planets in disks evolving via disk winds and implications for the origin of the solar system’s terrestrial planets

¹ Observatoire de la Côte d’Azur, Boulevard de l’Observatoire, 06304 Nice Cedex 4, France
e-mail: omasahiro@oca.eu
² Nagoya University, Furo-cho, Chikusa-ku, Nagoya, Aichi 464-8602, Japan

Received: 9 January 2015
Accepted: 20 April 2015

Abstract

Context. Recent three-dimensional magnetohydrodynamical simulations have identified a disk wind by which gas materials are lost from the surface of a protoplanetary disk, which can significantly alter the evolution of the inner disk and the formation of terrestrial planets. A simultaneous description of the realistic evolution of the gaseous and solid components in a disk may provide a clue for solving the problem of the mass concentration of the terrestrial planets in the solar system.

Aims. We simulate the formation of terrestrial planets from planetary embryos in a disk that evolves via magnetorotational instability and a disk wind. The aim is to examine the effects of a disk wind on the orbital evolution and final configuration of planetary systems.

Methods. We perform N-body simulations of sixty 0.1 Earth-mass embryos in an evolving disk. The evolution of the gas surface density of the disk is tracked by solving a one-dimensional diffusion equation with a sink term that accounts for the disk wind.

Results. We find that even in the case of a weak disk wind, the radial slope of the gas surface density of the inner disk becomes shallower, which slows or halts the Type I migration of embryos. If the effect of the disk wind is strong, the disk profile is significantly altered (e.g., positive surface density gradient, inside-out evacuation), leading to outward migration of embryos inside ~1 AU.

Conclusions. Disk winds play an essential role in terrestrial planet formation inside a few AU by changing the disk profile. In addition, embryos can undergo convergent migration to ~1 AU in certainly probable conditions. In such a case, the characteristic features of the solar system’s terrestrial planets (e.g., mass concentration around 1 AU, late giant impact) may be reproduced.