Book contents
- Frontmatter
- Contents
- Preface
- List of Participants
- Magnetic Noise and the Galactic Dynamo
- On the Oscillation in Model Z
- Nonlinear Dynamos in a Spherical Shell
- The Onset of Dynamo Action in Alpha-lambda Dynamos
- Multifractality, Near-singularities and the Role of Stretching in Turbulence
- Note on Perfect Fast Dynamo Action in a Large-amplitude SFS Map
- A Thermally Driven Disc Dynamo
- Magnetic Instabilities in Rapidly Rotating Systems
- Modes of a Flux Ring Lying in the Equator of a Star
- A Nonaxisymmetric Dynamo in Toroidal Geometry
- Simulating the Interaction of Convection with Magnetic Fields in the Sun
- Experimental Aspects of a Laboratory Scale Liquid Sodium Dynamo Model
- Influence of the Period of an ABC Flow on its Dynamo Action
- Numerical Calculations of Dynamos for ABC and Related Flows
- Local Helicity, a Material Invariant for the Odd-dimensional Incompressible Euler Equations
- On the Quasimagnetostrophic Asymptotic Approximation Related to Solar Activity
- Simple Dynamical Fast Dynamos
- A Numerical Study of Dynamos in Spherical Shells with Conducting Boundaries
- Non-axisymmetric Shear Layers in a Rotating Spherical Shell
- Testing for Dynamo Action
- Alpha-quenching in Cylindrical Magnetoconvection
- On the Stretching of Line Elements in Fluids: an Approach from Differential Geometry
- Instabilities of Tidally and Precessionally Induced Flows
- Probability Distribution of Passive Scalars with Nonlinear Mean Gradient
- Magnetic Fluctuations in Fast Dynamos
- A Statistical Description of MHD Turbulence in Laboratory Plasmas
- Compressible Magnetoconvection in Three Dimensions
- The Excitation of Nonaxisymmetric Magnetic Fields in Galaxies
- Localized Magnetic Fields in a Perfectly Conducting Fluid
- Turbulent Dynamo and the Geomagnetic Secular Variation
- On-Off Intermittency: General Description and Feedback Model
- Dynamo Action in a Nearly Integrable Chaotic Flow
- The Dynamo Mechanism in the Deep Convection Zone of the Sun
- Shearing Instabilities in Magnetoconvection
- On the Role of Rotation of the Internal Core Relative to the Mantle
- Evolution of Magnetic Fields in a Swirling Jet
- Analytic Fast Dynamo Solution for a Two-dimensional Pulsed Flow
- On Magnetic Dynamos in Thin Accretion Disks Around Compact and Young Stars
- The Strong Field Branch of the Childress–Soward Dynamo
- Evidence for the Suppression of the Alpha-effect by Weak Magnetic Fields
- Turbulent Magnetic Transport Effects and their Relation to Magnetic Field Intermittency
- Proving the Existence of Negative Isotropic Eddy Viscosity
- Dynamo Action Induced by Lateral Variation of Electrical Conductivity
- Spherical Inertial Oscillation and Convection
- Hydrodynamic Stability of the ABC Flow
- Dynamos with Ambipolar Diffusion
- Subject Index
On Magnetic Dynamos in Thin Accretion Disks Around Compact and Young Stars
Published online by Cambridge University Press: 11 May 2010
- Frontmatter
- Contents
- Preface
- List of Participants
- Magnetic Noise and the Galactic Dynamo
- On the Oscillation in Model Z
- Nonlinear Dynamos in a Spherical Shell
- The Onset of Dynamo Action in Alpha-lambda Dynamos
- Multifractality, Near-singularities and the Role of Stretching in Turbulence
- Note on Perfect Fast Dynamo Action in a Large-amplitude SFS Map
- A Thermally Driven Disc Dynamo
- Magnetic Instabilities in Rapidly Rotating Systems
- Modes of a Flux Ring Lying in the Equator of a Star
- A Nonaxisymmetric Dynamo in Toroidal Geometry
- Simulating the Interaction of Convection with Magnetic Fields in the Sun
- Experimental Aspects of a Laboratory Scale Liquid Sodium Dynamo Model
- Influence of the Period of an ABC Flow on its Dynamo Action
- Numerical Calculations of Dynamos for ABC and Related Flows
- Local Helicity, a Material Invariant for the Odd-dimensional Incompressible Euler Equations
- On the Quasimagnetostrophic Asymptotic Approximation Related to Solar Activity
- Simple Dynamical Fast Dynamos
- A Numerical Study of Dynamos in Spherical Shells with Conducting Boundaries
- Non-axisymmetric Shear Layers in a Rotating Spherical Shell
- Testing for Dynamo Action
- Alpha-quenching in Cylindrical Magnetoconvection
- On the Stretching of Line Elements in Fluids: an Approach from Differential Geometry
- Instabilities of Tidally and Precessionally Induced Flows
- Probability Distribution of Passive Scalars with Nonlinear Mean Gradient
- Magnetic Fluctuations in Fast Dynamos
- A Statistical Description of MHD Turbulence in Laboratory Plasmas
- Compressible Magnetoconvection in Three Dimensions
- The Excitation of Nonaxisymmetric Magnetic Fields in Galaxies
- Localized Magnetic Fields in a Perfectly Conducting Fluid
- Turbulent Dynamo and the Geomagnetic Secular Variation
- On-Off Intermittency: General Description and Feedback Model
- Dynamo Action in a Nearly Integrable Chaotic Flow
- The Dynamo Mechanism in the Deep Convection Zone of the Sun
- Shearing Instabilities in Magnetoconvection
- On the Role of Rotation of the Internal Core Relative to the Mantle
- Evolution of Magnetic Fields in a Swirling Jet
- Analytic Fast Dynamo Solution for a Two-dimensional Pulsed Flow
- On Magnetic Dynamos in Thin Accretion Disks Around Compact and Young Stars
- The Strong Field Branch of the Childress–Soward Dynamo
- Evidence for the Suppression of the Alpha-effect by Weak Magnetic Fields
- Turbulent Magnetic Transport Effects and their Relation to Magnetic Field Intermittency
- Proving the Existence of Negative Isotropic Eddy Viscosity
- Dynamo Action Induced by Lateral Variation of Electrical Conductivity
- Spherical Inertial Oscillation and Convection
- Hydrodynamic Stability of the ABC Flow
- Dynamos with Ambipolar Diffusion
- Subject Index
Summary
A variety of geometrically thin accretion disks commonly associated with such astronomical objects as X-ray binaries, cataclysmic variables, and protostars are likely to be seats of MHD dynamo actions. Thin disk geometry and the particular physical environment make accretion disk dynamos different from stellar, planetary, or even galactic dynamos. We discuss those particular features of disk dynamos with emphasis on the difference between protoplanetary disk dynamos and those associated with compact stars. We then describe normal mode solutions for thin disk dynamos and discuss implications for the dynamical behavior of dynamo-magnetized accretion disks.
INTRODUCTION
It is widely appreciated that magnetic fields can play an important role in accretion disk dynamics. Shakura & Sunyaev (1973), in their well known paper, pointed to magnetic fields as the source of a viscous couple necessary for the accretion to take place. Disk magnetic fields have also been invoked to explain spectra of compact X-ray sources, as a source of coronal heating, and as a source of wind production. In the context of the Solar nebula, which is widely assumed to represent a typical protoplanetary disk, the existence of a magnetic field is inferred from the residual magnetization of primitive meteorites, which are assumed to owe their magnetization to nebular magnetic fields. However, in a typical accretion disk, the timescale for ohmic dissipation is much smaller than the typical radial infall time, thus it is difficult to see how any magnetic field contained in the gas that falls onto the disk can persist long enough to be dynamically or otherwise important, unless it is regenerated by a dynamo cycle.
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- Solar and Planetary Dynamos , pp. 287 - 294Publisher: Cambridge University PressPrint publication year: 1994