Angular Momentum Transport in Accretion Disks: Scaling Laws in MRI-driven Turbulence
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Angular Momentum Transport in Accretion Disks : Scaling Laws in MRI-driven Turbulence. / E. Pessah, Martin; Chan, Chi-kwan; Psaltis, Dimitrios; Pessah, Martin Elias.
I: Astrophysical Journal Letters, Bind 668, Nr. 1, 10.10.2007, s. L51-L54.Publikation: Bidrag til tidsskrift › Tidsskriftartikel › Forskning › fagfællebedømt
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TY - JOUR
T1 - Angular Momentum Transport in Accretion Disks
T2 - Scaling Laws in MRI-driven Turbulence
AU - E. Pessah, Martin
AU - Chan, Chi-kwan
AU - Psaltis, Dimitrios
AU - Pessah, Martin Elias
PY - 2007/10/10
Y1 - 2007/10/10
N2 - We present a scaling law that predicts the values of the stresses obtained in numerical simulations of saturated MRI-driven turbulence in non-stratified shearing boxes. It relates the turbulent stresses to the strength of the vertical magnetic field, the sound speed, the vertical size of the box, and the numerical resolution and predicts accurately the results of 35 numerical simulations performed for a wide variety of physical conditions. We use our result to show that the saturated stresses in simulations with zero net magnetic flux depend linearly on the numerical resolution and would become negligible if the resolution were set equal to the natural dissipation scale in astrophysical disks. We conclude that, in order for MRI-driven turbulent angular momentum transport to be able to account for the large value of the effective alpha viscosity inferred observationally, the disk must be threaded by a significant vertical magnetic field and the turbulent magnetic energy must be in near equipartition with the thermal energy. This result has important implications for the spectra of accretion disks and their stability.
AB - We present a scaling law that predicts the values of the stresses obtained in numerical simulations of saturated MRI-driven turbulence in non-stratified shearing boxes. It relates the turbulent stresses to the strength of the vertical magnetic field, the sound speed, the vertical size of the box, and the numerical resolution and predicts accurately the results of 35 numerical simulations performed for a wide variety of physical conditions. We use our result to show that the saturated stresses in simulations with zero net magnetic flux depend linearly on the numerical resolution and would become negligible if the resolution were set equal to the natural dissipation scale in astrophysical disks. We conclude that, in order for MRI-driven turbulent angular momentum transport to be able to account for the large value of the effective alpha viscosity inferred observationally, the disk must be threaded by a significant vertical magnetic field and the turbulent magnetic energy must be in near equipartition with the thermal energy. This result has important implications for the spectra of accretion disks and their stability.
KW - astro-ph
U2 - 10.1086/522585
DO - 10.1086/522585
M3 - Journal article
VL - 668
SP - L51-L54
JO - Astrophysical Journal
JF - Astrophysical Journal
SN - 0004-637X
IS - 1
ER -
ID: 34382948