Impact of convection and resistivity on angular momentum transport in dwarf novae

Abstract

The eruptive cycles of dwarf novae (DN) are thought to be due to a thermal-viscous instability in the accretion disk surrounding the white dwarf (WD). This model has long been known to imply a stress to pressure ratio α~0.1 in outburst compared to α~ 0.01 in quiescence. Such an enhancement in $\alpha$ has recently been observed in simulations of turbulent transport driven by the magneto-rotational instability (MRI) when convection is present, without requiring a net magnetic flux. We independently recover this result by carrying out PLUTO MHD simulations of vertically stratified, radiative, shearing boxes with the thermodynamics and opacities appropriate to DN. The results are robust against the choice of vertical boundary conditions. The thermal equilibrium solutions found by the simulations trace the well-known S-curve in the density-temperature plane. We confirm that the high values of α~ 0.1 occur near the tip of the hot branch of the S-curve, where convection is active. However, we also present thermally-stable simulations at lower temperatures that have standard values of α~ 0.03 despite the presence of vigorous convection. We find no simple relationship between αand the strength of the convection, as measured by the ratio of convective to radiative flux. The cold branch is only very weakly ionized so, in the second part of this work, we studied the impact of non-ideal MHD effects on transport. We include resistivity in the simulations and find that the MRI-driven transport is quenched (α~ 0) below the critical density at which the magnetic Reynolds number R_m \leq 10^4. This is problematic as X-ray emission observed in quiescent systems requires ongoing accretion onto the WD. We verify that these X-rays cannot self-sustain MRI-driven turbulence by photo-ionizing the disk and discuss possible solutions to the issue of accretion in quiescence.

arXiv comment14 pages, 13 figures, 1 table; accepted for publication in A&A

References in corpus (32)

• Low Temperature Opacities
• The disc instability model of dwarf-novae and low-mass X-ray binary transients
• Magnetic fields of non-degenerate stars
• Accretion disc viscosity: how big is alpha?
• Linear Analysis of the Hall Effect in Protostellar Disks
• X-ray Emissions from Accreting White Dwarfs: a Review
• The ionization fraction in alpha-models of protoplanetary disks
• Local Study of Accretion Disks with a Strong Vertical Magnetic Field: Magnetorotational Instability and Disk Outflow
• The Effect of Resistivity on the Nonlinear Stage of the Magnetorotational Instability in Accretion Disks
• Effect of Ambipolar Diffusion on the Non-linear Evolution of Magnetorotational Instability in Weakly Ionized Disks
• A Module for Radiation Hydrodynamic Calculations With ZEUS-2D Using Flux-Limited Diffusion
• The Effect of the Hall Term on the Nonlinear Evolution of the Magnetorotational Instability: II. Saturation Level and Critical Magnetic Reynolds Number
• On the origin of episodic accretion in Dwarf Novae
• Accretion disc dynamo activity in local simulations spanning weak-to-strong net vertical magnetic flux regimes
• Magnetic self-organisation in Hall-dominated magnetorotational turbulence
• Emergent Mesoscale Phenomena in Magnetized Accretion Disc Turbulence
• Nonlinear Evolution of the Magnetorotational Instability in Ion-Neutral Disks
• Convection Causes Enhanced Magnetic Turbulence in Accretion Disks in Outburst
• Radiation Magnetohydrodynamics In Global Simulations Of Protoplanetary Disks
• Deriving an X-ray luminosity function of dwarf novae based on parallax measurements
• The viscosity parameter alpha and the properties of accretion disc outbursts in close binaries
• The Kepler light curves of V1504 Cygni and V344 Lyrae: A study of the Outburst Properties
• Structure and properties of transition fronts in accretion discs
• Spiral-driven accretion in protoplanetary discs - I. 2D models
• Viscosity Mechanisms in Accretion Disks
• The Kepler Light Curve of V344 Lyrae: Constraining the Thermal-Viscous Limit Cycle Instability
• Dwarf Nova Outbursts with Magnetorotational Turbulence
• Resolution Dependence of Magnetorotational Turbulence in the Isothermal Stratified Shearing Box
• Magnetic Turbulence and Thermodynamics in the Inner Region of Protoplanetary Discs
• Hysteresis and thermal limit cycles in MRI simulations of accretion discs
• Global MHD Simulations of Accretion Disks in Cataclysmic Variables (CVs): II The Relative Importance of MRI and Spiral Shocks
• Convective Quenching of Field Reversals in Accretion Disc Dynamos

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