Accretion disc backflow in resistive MHD simulations

Abstract

We investigate accretion onto a central star, with the size, rotation rate, and magnetic dipole of a young stellar object, to study the flow pattern (velocity and density) of the fluid within and outside of the disc. We perform resistive MHD simulations of thin $\alpha$-discs, varying the parameters such as the stellar rotation rate and magnetic field, and (anomalous) coefficients of viscosity and resistivity in the disc. To provide a benchmark for the results and to compare with known analytic results, we also perform purely hydrodynamic simulations (HD) for the same problem. Although obtained for a different situation with differing inner boundary condition, the disc structure in the HD simulations closely follows the analytic solution of Kluźniak and Kita (2000) -- in particular a region of "midplane" backflow exists in the right range of radii, depending on the viscosity parameter. In the MHD solutions, whenever the magnetic Prandtl number does not exceed a certain critical value, the midplane backflow exists throughout the accretion disc, extending all the way down to the inner transition zone where the disc transitions to a magnetic funnel flow. For values of the magnetic Prandtl number close to the critical value the backflow and the inner disc undergo a quasiperiodic radial oscillation, otherwise the backflow is steady, as is the disc solution. From our results, supplemented by our reading of the literature, we conclude that midplane backflow is a real feature of at least some accretion discs, whether HD $\alpha$-discs or MHD discs, including ones driven by MRI turbulence.

arXiv comment11 pages, 11 figures, 1 table Submitted to Monthly Notices of the Royal Astronomical Society (MNRAS)

References in corpus (25)

• PLUTO: a Numerical Code for Computational Astrophysics
• Radial Flow of Dust Particles in Accretion Disks
• Enhanced Angular Momentum Transport in Accretion Disks
• Observations of Protoplanetary Disk Structures
• MHD simulations of accretion onto a dipolar magnetosphere. II. Magnetospheric ejections and stellar spin-down
• Global Evolution of an Accretion Disk with Net Vertical Field: Coronal Accretion, Flux Transport, and Disk Winds
• Turbulence and Steady Flows in 3D Global Stratified MHD Simulations of Accretion Disks
• MHD Simulations of Global Accretion Disks with Vertical Magnetic Fields
• The Turbulent Magnetic Prandtl Number of MHD Turbulence in Disks
• Two-Dimensional Transport of Solids in Viscous Protoplanetary Disks
• Strongly magnetized accretion disks: structure and accretion from global magnetohydrodynamic simulations
• Accretion discs around black holes: two dimensional, advection cooled flows
• Turbulent resistivity evaluation in MRI generated turbulence
• Convection Causes Enhanced Magnetic Turbulence in Accretion Disks in Outburst
• Accretion disks around black holes: dynamical evolution, meridional circulations and gamma ray bursts
• Meridional circulation in turbulent protoplanetary disks
• Magnetic torques on T Tauri stars: accreting vs. non-accreting systems
• The Structure of Radiatively Inefficient Black Hole Accretion Flows
• Asymptotic models of meridional flows in thin viscous accretion disks
• On vertical variations of gas flow in protoplanetary disks and their impact on the transport of solids
• Accretion discs with non-zero central torque
• Radial Transport and Meridional Circulation in Accretion Disks
• Inner dusty regions of protoplanetary discs -- II. Dust dynamics driven by radiation pressure and disc winds
• "Atlas" of numerical solutions for star-disk magnetospheric interaction
• Backflow in simulated MHD accretion disks

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• Magnetically threaded accretion disks in resistive magnetohydrodynamic simulations and asymptotic expansion
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• Inner dusty regions of protoplanetary discs -- III. The role of non-radial radiation pressure in dust dynamics
• Multipolar magnetic configuration: a trace of post-mergers events in circumstellar disks around FS CMa Stars