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Multifluid simulations of the magnetorotational instability in accretion disks around protostars

O'Keeffe, Wayne (2013) Multifluid simulations of the magnetorotational instability in accretion disks around protostars. PhD thesis, Dublin City University.

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Abstract

Turbulence is believed to be of importance in molecular cloud formation as well as the star formation processes within them, such as accretion of matter onto young stars from the surrounding accretion disk. The kinetic viscosity associated with differentially rotating accretion disks is not believed to be strong enough to account for observed accretion rates. Turbulent motion, driven by the magnetorotational instability (MRI), may provide an anomalous viscosity well in excess of the kinetic viscosity alone leading to enhanced transport of angular momentum, resulting in a higher rate of accretion onto the forming star. We perform large-scale 3D multifluid simulations of a weakly ionised accretion disk and examine the development and saturation of the turbulence driven by the MRI. This numerical study is carried out using the multifluid MHD code HYDRA. An important effect of multifluid MHD is diffusion of the magnetic field. Simulations which isolate ambipolar and Hall diffusion are studied individually and comparisons between these and ideal MHD and full multifluid simulations are presented. The stresses (magnetic and kinetic) and an estimation of the anomalous viscosity are calculated for all models. From this information we can determine how accretion is affected by the multifluid physics in the presence of the MRI.

Item Type:Thesis (PhD)
Date of Award:November 2013
Refereed:No
Supervisor(s):Downes, Turlough P.
Uncontrolled Keywords:Star formation; Planet formation; Accretion disks, Young stellar objects
Subjects:Physical Sciences > Astronomy > Astrophysics
Physical Sciences > Plasmas
Mathematics > Mathematical physics
Computer Science > Computer simulation
DCU Faculties and Centres:Research Initiatives and Centres > Scientific Computing and Complex Systems Modelling (Sci-Sym)
Research Initiatives and Centres > National Centre for Plasma Science and Technology (NCPST)
DCU Faculties and Schools > Faculty of Science and Health > School of Mathematical Sciences
Use License:This item is licensed under a Creative Commons Attribution-NonCommercial-No Derivative Works 3.0 License. View License
Funders:Science Foundation Ireland
ID Code:18570
Deposited On:03 Dec 2013 11:40 by Turlough Downes. Last Modified 03 Dec 2013 11:40

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