On Hydromagnetic Stresses in Accretion Disk Boundary Layers

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On Hydromagnetic Stresses in Accretion Disk Boundary Layers. / Pessah, Martin Elias; Chan, Chi-kwan.

I: Astrophysical Journal, Bind 751, Nr. 1, 01.05.2012, s. 48.

Publikation: Bidrag til tidsskriftTidsskriftartikelForskningfagfællebedømt

Harvard

Pessah, ME & Chan, C 2012, 'On Hydromagnetic Stresses in Accretion Disk Boundary Layers', Astrophysical Journal, bind 751, nr. 1, s. 48. https://doi.org/10.1088/0004-637X/751/1/48

APA

Pessah, M. E., & Chan, C. (2012). On Hydromagnetic Stresses in Accretion Disk Boundary Layers. Astrophysical Journal, 751(1), 48. https://doi.org/10.1088/0004-637X/751/1/48

Vancouver

Pessah ME, Chan C. On Hydromagnetic Stresses in Accretion Disk Boundary Layers. Astrophysical Journal. 2012 maj 1;751(1):48. https://doi.org/10.1088/0004-637X/751/1/48

Author

Pessah, Martin Elias ; Chan, Chi-kwan. / On Hydromagnetic Stresses in Accretion Disk Boundary Layers. I: Astrophysical Journal. 2012 ; Bind 751, Nr. 1. s. 48.

Bibtex

@article{9f8f0bf3c06f4886bb38e335628974e8,
title = "On Hydromagnetic Stresses in Accretion Disk Boundary Layers",
abstract = "Detailed calculations of the physical structure of accretion disk boundary layers, and thus their inferred observational properties, rely on the assumption that angular momentum transport is opposite to the radial angular frequency gradient of the disk. The standard model for turbulent shear viscosity satisfies this assumption by construction. However, this behavior is not supported by numerical simulations of turbulent magnetohydrodynamic (MHD) accretion disks, which show that angular momentum transport driven by the magnetorotational instability (MRI) is inefficient in disk regions where, as expected in boundary layers, the angular frequency increases with radius. In order to shed light on physically viable mechanisms for angular momentum transport in this inner disk region, we examine the generation of hydromagnetic stresses and energy density in differentially rotating backgrounds with angular frequencies that increase outward in the shearing-sheet framework. We isolate the modes that are unrelated to the standard MRI and provide analytic solutions for the long-term evolution of the resulting shearing MHD waves. We show that, although the energy density of these waves can be amplified significantly, their associated stresses oscillate around zero, rendering them an inefficient mechanism to transport significant angular momentum (inward). These findings are consistent with the results obtained in numerical simulations of MHD accretion disk boundary layers and challenge the standard assumption of efficient angular momentum transport in the inner disk regions. This suggests that the detailed structure of turbulent MHD accretion disk boundary layers could differ appreciably from those derived within the standard framework of turbulent shear viscosity",
author = "Pessah, {Martin Elias} and Chi-kwan Chan",
year = "2012",
month = may,
day = "1",
doi = "10.1088/0004-637X/751/1/48",
language = "English",
volume = "751",
pages = "48",
journal = "Astrophysical Journal",
issn = "0004-637X",
publisher = "Institute of Physics Publishing, Inc",
number = "1",

}

RIS

TY - JOUR

T1 - On Hydromagnetic Stresses in Accretion Disk Boundary Layers

AU - Pessah, Martin Elias

AU - Chan, Chi-kwan

PY - 2012/5/1

Y1 - 2012/5/1

N2 - Detailed calculations of the physical structure of accretion disk boundary layers, and thus their inferred observational properties, rely on the assumption that angular momentum transport is opposite to the radial angular frequency gradient of the disk. The standard model for turbulent shear viscosity satisfies this assumption by construction. However, this behavior is not supported by numerical simulations of turbulent magnetohydrodynamic (MHD) accretion disks, which show that angular momentum transport driven by the magnetorotational instability (MRI) is inefficient in disk regions where, as expected in boundary layers, the angular frequency increases with radius. In order to shed light on physically viable mechanisms for angular momentum transport in this inner disk region, we examine the generation of hydromagnetic stresses and energy density in differentially rotating backgrounds with angular frequencies that increase outward in the shearing-sheet framework. We isolate the modes that are unrelated to the standard MRI and provide analytic solutions for the long-term evolution of the resulting shearing MHD waves. We show that, although the energy density of these waves can be amplified significantly, their associated stresses oscillate around zero, rendering them an inefficient mechanism to transport significant angular momentum (inward). These findings are consistent with the results obtained in numerical simulations of MHD accretion disk boundary layers and challenge the standard assumption of efficient angular momentum transport in the inner disk regions. This suggests that the detailed structure of turbulent MHD accretion disk boundary layers could differ appreciably from those derived within the standard framework of turbulent shear viscosity

AB - Detailed calculations of the physical structure of accretion disk boundary layers, and thus their inferred observational properties, rely on the assumption that angular momentum transport is opposite to the radial angular frequency gradient of the disk. The standard model for turbulent shear viscosity satisfies this assumption by construction. However, this behavior is not supported by numerical simulations of turbulent magnetohydrodynamic (MHD) accretion disks, which show that angular momentum transport driven by the magnetorotational instability (MRI) is inefficient in disk regions where, as expected in boundary layers, the angular frequency increases with radius. In order to shed light on physically viable mechanisms for angular momentum transport in this inner disk region, we examine the generation of hydromagnetic stresses and energy density in differentially rotating backgrounds with angular frequencies that increase outward in the shearing-sheet framework. We isolate the modes that are unrelated to the standard MRI and provide analytic solutions for the long-term evolution of the resulting shearing MHD waves. We show that, although the energy density of these waves can be amplified significantly, their associated stresses oscillate around zero, rendering them an inefficient mechanism to transport significant angular momentum (inward). These findings are consistent with the results obtained in numerical simulations of MHD accretion disk boundary layers and challenge the standard assumption of efficient angular momentum transport in the inner disk regions. This suggests that the detailed structure of turbulent MHD accretion disk boundary layers could differ appreciably from those derived within the standard framework of turbulent shear viscosity

U2 - 10.1088/0004-637X/751/1/48

DO - 10.1088/0004-637X/751/1/48

M3 - Journal article

VL - 751

SP - 48

JO - Astrophysical Journal

JF - Astrophysical Journal

SN - 0004-637X

IS - 1

ER -

ID: 40263553