2008/08/28 by Caroline E. J. M. L. J. Terquem · 3 citations
Physics and Astronomy · #Astronomy and Astrophysical Research #Astrophysics and Star Formation Studies #Composite number #Ionization #Plasma #Protoplanetary disk #Scientific Research and Discoveries #Stars #astro-ph
paper · pdf · doi:10.1086/592597
13 pages, 5 figures, accepted for publication in ApJ
arxiv created 2008/08/28 · openalex publication_date 2008/11/22 · arxiv updated 2009/12/01 · openalex created_date 2025/10/10 · openalex updated_date 2026/08/05
We study an accretion disk in which three different regions can coexist: MHD turbulent regions, dead zones, and gravitationally unstable regions. Although the dead zones are stable, there is some transport due to the Reynolds stress associated with waves emitted from the turbulent layers. We model the transport in each of the different regions by its own α parameter, which is 10-10 3 times smaller in dead zones than in active layers. In gravitationally unstable regions, α is determined by the fact that the disk self-adjusts to a state of marginal stability. We construct steady-state models of such disks. We find that for uniform mass flow, the disk has to be more massive, hotter, and thicker at the radii where there is a dead zone. In disks in which the dead zone is very massive, gravitational instabilities are present. Whether such models are realistic or not depends on whether hydrodynamical fluctuations driven by the turbulent layers can penetrate all the way inside the dead zone. If the disk is not in a steady state at some stage of its evolution, then the surface density will evolve toward the steady-state solution. However, if the value of α in the dead zone is much smaller than that in the active zone, the timescale for the parts of the disk that are beyond a few AU to reach a steady state can become longer than the disk lifetime. Steady-state disks with dead zones are a more favorable environment for planet formation than are standard disks, since the dead zone is typically 10 times more massive than a corresponding turbulent zone at the same location.