Global Drag-induced Instabilities in Protoplanetary Disks
Abstract
We use the Fokker-Planck equation and model the dispersive dynamics of solid particles in annular protoplanetary disks whose gas component is more massive than the particle phase. We model particle-gas interactions as hard sphere collisions, determine the functional form of diffusion coefficients, and show the existence of two global unstable modes in the particle phase. These modes have spiral patterns with the azimuthal wavenumber m = 1 and rotate slowly. We show that in ring-shaped disks, the phase-space density of solid particles increases linearly in time toward an accumulation point near the location of pressure maximum, while instabilities grow exponentially. Therefore, planetesimals and planetary cores can be efficiently produced near the peaks of unstable density waves. In this mechanism, particles migrating toward the accumulation point will not participate in the formation of planets, and should eventually form a debris ring like the main asteroid belt or classical Kuiper Belt objects. We present the implications of global instabilities to the formation of ice giants and terrestrial planets in the solar system.
- Publication:
-
The Astrophysical Journal
- Pub Date:
- July 2013
- DOI:
- 10.1088/0004-637X/772/1/75
- arXiv:
- arXiv:1301.2064
- Bibcode:
- 2013ApJ...772...75J
- Keywords:
-
- hydrodynamics;
- instabilities;
- methods: numerical;
- planetary systems;
- planets and satellites: formation;
- protoplanetary disks;
- Astrophysics - Earth and Planetary Astrophysics;
- Physics - Fluid Dynamics
- E-Print:
- 11 pages, 5 Figures, 2 Tables, accepted for publication in the Astrophysical Journal (revised version with applications to planet formation in the solar system)