Coronae & Outflows from Helical Dynamos, Compatibility with the MRI, and Application to Protostellar Disks

Abstract

Magnetically mediated disk outflows are a leading paradigm to explain winds and jets in a variety of astrophysical sources, but where do the fields come from? Since accretion of mean magnetic flux may be disfavored in a thin turbulent disk, and only fields generated with sufficiently large scale can escape before being shredded by turbulence, in situ field production is desirable. Nonlinear helical inverse dynamo theory can provide the desired fields for coronae and outflows. We discuss the implications for contemporary protostellar disks, where the MRI (magneto-rotational instability) can drive turbulence in the inner regions, and primordial protostellar disks, where gravitational instability drives the turbulence. We emphasize that helical dynamos are compatible with the magneto-rotational instability, and clarify the relationship between the two.

12 pages, LaTeX (with figs); version in press for "Proceedings of the International Workshop on Magnetic Fields and Star Formation: Theory vs. Observation" Madrid, Spain; April 2003

References in corpus (3)

• The Formation of the First Stars I. Mass Infall Rates, Accretion Disk Structure and Protostellar Evolution
• Doubly Helical Coronal Ejections from Dynamos and their Role in Sustaining the Solar Cycle
• Protostellar Disk Dynamos and Hydromagnetic Outflows in Primordial Star Formation

Cited by in corpus (15)

• Angular Momentum Transport in Accretion Disks: Scaling Laws in MRI-driven Turbulence
• Saturation of the magnetorotational instability in the unstratified shearing box with zero net flux: convergence in taller boxes
• Coronae as Consequence of Large Scale Magnetic Fields in Turbulent Accretion Disks
• A mean-field approach to the propagation of field patterns in stratified magneto rotational turbulence
• Magnetic Field Upper Limits for Jet Formation
• On the convergence of Magnetorotational turbulence in stratified isothermal shearing boxes
• Electromotive force due to magnetohydrodynamic fluctuations in sheared rotating turbulence
• Convective Quenching of Field Reversals in Accretion Disc Dynamos
• Heating of Accretion-Disk Coronae and Jets by General Relativistic MHD Turbulence
• Vertical Structure and Coronal Power of Accretion Disks Powered by MRI Turbulence
• 3D global simulations of RIAFs: convergence, effects of azimuthal extent and dynamo
• Oscillating Ponomarenko dynamo in the highly conducting limit
• Bihelical Magnetic Relaxation and Large Scale Magnetic Field Growth
• MRI turbulence in vertically stratified accretion discs at large magnetic Prandtl numbers
• Shedding light on the MRI driven dynamo in a stratified shearing box