The global baroclinic instability in accretion disks. II. Local linear analysis

被引:67
作者
Klahr, H
机构
[1] Max Planck Inst Astron, D-69117 Heidelberg, Germany
[2] Univ Calif Santa Cruz, Univ Calif Observ, Lick Observ, Santa Cruz, CA 95060 USA
关键词
accretion; accretion disks; circumstellar matter; hydrodynamics; instabilities; methods : numerical; turbulence;
D O I
10.1086/383119
中图分类号
P1 [天文学];
学科分类号
0704 ;
摘要
This paper contains a local linear stability analysis for accretion disks under the influence of a global radial entropy gradient beta = - d log T/d log r for constant surface density. Numerical simulations suggested the existence of an instability in two- and three-dimensional models of the solar nebula. The present paper tries to clarify, quantify, and explain such a global baroclinic instability for two- dimensional flat accretion disk models. As a result, linear theory predicts a transient linear instability that will amplify perturbations only for a limited time or up to a certain finite amplification. This can be understood as a result of the growth time of the instability being longer than the shear time, which destroys the modes that are able to grow. Thus, only nonlinear effects can lead to a relevant amplification. Nevertheless, a lower limit on the entropy gradient alphabeta approximate to 0.22 for the transient linear instability is derived, which can be tested in future nonlinear simulations. This would help to explain the observed instability in numerical simulations as an ultimate result of the transient linear instability, i.e., the global baroclinic instability.
引用
收藏
页码:1070 / 1082
页数:13
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