Magnetorotational Instability in Protoplanetary Disks. II. Ionization State and Unstable Regions
Abstract
We investigate where magnetorotational instability operates in protoplanetary disks, which can cause angular momentum transport in the disks. We investigate the spatial distribution of various charged particles and the unstable regions for a variety of models for protoplanetary disks, taking into account the recombination of ions and electrons at grain surfaces, which is an important process in most parts of the disks. We find that for all the models there is an inner region that is magnetorotationally stable due to ohmic dissipation. This must make the accretion onto the central star nonsteady. For the model of the minimum-mass solar nebula, the critical radius, inside of which the disk is stable, is about 20 AU, and the mass accretion rate just outside the critical radius is 10-7-10-6 Msolar yr-1. The stable region is smaller in a disk of lower column density. Dust grains in protoplanetary disks may grow by mutual sticking and may sediment toward the midplane of the disks. We find that the stable region shrinks as the grain size increases or the sedimentation proceeds. Therefore, in the late evolutionary stages, protoplanetary disks can be magnetorotationally unstable even in the inner regions.
- Publication:
-
The Astrophysical Journal
- Pub Date:
- November 2000
- DOI:
- 10.1086/317075
- arXiv:
- arXiv:astro-ph/0005464
- Bibcode:
- 2000ApJ...543..486S
- Keywords:
-
- Accretion;
- Accretion Disks;
- Diffusion;
- Instabilities;
- Magnetohydrodynamics: MHD;
- Stars: Planetary Systems;
- Solar System: Formation;
- Astrophysics
- E-Print:
- 23 pages + 16 figures + 3 tables, accepted for publication in ApJ