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Angular momentum transport and large eddy simulations in magnetorotational turbulence: the small Pm limit
- Source :
- Astronomy and Astrophysics-A&A, Astronomy and Astrophysics-A&A, 2015, 579, pp.A117. ⟨10.1051/0004-6361/201525688⟩, Astronomy and Astrophysics-A&A, EDP Sciences, 2015, 579, pp.A117. ⟨10.1051/0004-6361/201525688⟩
- Publication Year :
- 2015
- Publisher :
- HAL CCSD, 2015.
-
Abstract
- Angular momentum transport in accretion discs is often believed to be due to magnetohydrodynamic turbulence mediated by the magnetorotational instability. Despite an abundant literature on the MRI, the parameters governing the saturation amplitude of the turbulence are poorly understood and the existence of an asymptotic behavior in the Ohmic diffusion regime is not clearly established. We investigate the properties of the turbulent state in the small magnetic Prandtl number limit. Since this is extremely computationally expensive, we also study the relevance and range of applicability of the most common subgrid scale models for this problem. Unstratified shearing boxes simulations are performed both in the compressible and incompressible limits, with a resolution up to 800 cells per disc scale height. The latter constitutes the largest resolution ever attained for a simulation of MRI turbulence. In the presence of a mean magnetic field threading the domain, angular momentum transport converges to a finite value in the small Pm limit. When the mean vertical field amplitude is such that {\beta}, the ratio between the thermal and magnetic pressure, equals 1000, we find {\alpha}~0.032 when Pm approaches zero. In the case of a mean toroidal field for which {\beta}=100, we find {\alpha}~0.018 in the same limit. Both implicit LES and Chollet-Lesieur closure model reproduces these results for the {\alpha} parameter and the power spectra. A reduction in computational cost of a factor at least 16 (and up to 256) is achieved when using such methods. MRI turbulence operates efficiently in the small Pm limit provided there is a mean magnetic field. Implicit LES offers a practical and efficient mean of investigation of this regime but should be used with care, particularly in the case of a vertical field. Chollet-Lesieur closure model is perfectly suited for simulations done with a spectral code.<br />Comment: Accepted for publication in A&A
- Subjects :
- Angular momentum
FOS: Physical sciences
Astrophysics
Magnetohydrodynamic turbulence
01 natural sciences
magnetohydrodynamics (MHD)
methods: numerical
accretion
Magnetorotational instability
0103 physical sciences
Magnetic pressure
Magnetic Prandtl number
010306 general physics
010303 astronomy & astrophysics
Solar and Stellar Astrophysics (astro-ph.SR)
Earth and Planetary Astrophysics (astro-ph.EP)
Physics
Turbulence
accretion disks
turbulence
protoplanetary disks
Fluid Dynamics (physics.flu-dyn)
Astronomy and Astrophysics
Physics - Fluid Dynamics
Computational physics
Magnetic field
Amplitude
Astrophysics - Solar and Stellar Astrophysics
Space and Planetary Science
[PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph]
Astrophysics - Earth and Planetary Astrophysics
Subjects
Details
- Language :
- English
- ISSN :
- 00046361
- Database :
- OpenAIRE
- Journal :
- Astronomy and Astrophysics-A&A, Astronomy and Astrophysics-A&A, 2015, 579, pp.A117. ⟨10.1051/0004-6361/201525688⟩, Astronomy and Astrophysics-A&A, EDP Sciences, 2015, 579, pp.A117. ⟨10.1051/0004-6361/201525688⟩
- Accession number :
- edsair.doi.dedup.....35917223ee9dc5e4023d8102b3682584