Linear stability of magnetized massive protoplanetary disks

Journal Article · Sun Jul 20 00:00:00 EDT 2014 · Astrophysical Journal

DOI:https://doi.org/10.1088/0004-637X/790/1/13· OSTI ID:22365617

Lin, Min-Kai ^[1]

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1. Canadian Institute for Theoretical Astrophysics, 60 Saint George Street, Toronto, ON M5S 3H8 (Canada)

Magnetorotational instability (MRI) and gravitational instability (GI) are the two principle routes to turbulent angular momentum transport in accretion disks. Protoplanetary disks (PPDs) may develop both. This paper aims to reinvigorate interest in the study of magnetized massive PPDs, starting from the basic issue of stability. The local linear stability of a self-gravitating, uniformly magnetized, differentially rotating, three-dimensional stratified disk subject to axisymmetric perturbations is calculated numerically. The formulation includes resistivity. It is found that the reduction in the disk thickness by self-gravity (SG) can decrease MRI growth rates; the MRI becomes global in the vertical direction, and MRI modes with small radial length scales are stabilized. The maximum vertical field strength that permits the MRI in a strongly self-gravitating polytropic disk with polytropic index Γ = 1 is estimated to be B{sub z,max}≃c{sub s0}Ω√(μ{sub 0}/16πG), where c{sub s0} is the midplane sound speed and Ω is the local angular velocity. In massive disks with layered resistivity, the MRI is not well localized to regions where the Elsasser number exceeds unity. For MRI modes with radial length scales on the order of the disk thickness, SG can enhance density perturbations, an effect that becomes significant in the presence of a strong toroidal field, and which depends on the symmetry of the underlying MRI mode. In gravitationally unstable disks where GI and MRI growth rates are comparable, the character of unstable modes can transition smoothly between MRI and GI. Implications for nonlinear simulations are discussed briefly.

• OSTI ID: 22365617
• Journal Information: Astrophysical Journal, Vol. 790, Issue 1; Other Information: Country of input: International Atomic Energy Agency (IAEA); ISSN 0004-637X
• Country of Publication: United States
• Language: English

Related Subjects

79 ASTROPHYSICS
COSMOLOGY AND ASTRONOMY
ACCRETION DISKS
ANGULAR MOMENTUM
ANGULAR VELOCITY
AXIAL SYMMETRY
DENSITY
DISTURBANCES
GRAVITATION
GRAVITATIONAL INSTABILITY
MAGNETOHYDRODYNAMICS
NMR IMAGING
NONLINEAR PROBLEMS
PERTURBATION THEORY
PROTOPLANETS
SIMULATION
SOUND WAVES
STABILITY
THREE-DIMENSIONAL CALCULATIONS