The effects of vertical outflows on disk dynamos
نویسنده
چکیده
We consider the effect of vertical outflows on the mean-field dynamo in a thin disk. These outflows could be due to winds or magnetic buoyancy. We analyse both two-dimensional finite-difference numerical solutions of the axisymmetric dynamo equations and a free-decay mode expansion using the thin-disk approximation. Contrary to expectations, a vertical velocity can enhance dynamo action, provided the velocity is not too strong. In the nonlinear regime this can lead to super-exponential growth of the magnetic field.
منابع مشابه
Effect of the temperature profile of the accretion disk on the structure of jets and outflows around protostars
Magnetic fields play an important role in creating, driving, and in the evolution of outflows and jets from protostars and accretion disks. On the other hand, the temperature profile of the accretion disks may also affect the structure of the magnetic field and outflows. In this paper, we use the self-similar method in cylindrical coordinates to investigate the effect of the temperature profile...
متن کاملCoronae & Outflows from Helical Dynamos, Compatibility with the MRI, and Application to Protostellar Disks
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 hel...
متن کاملMagnetic fields in Planetary Nebulae Paradigms and Related MHD Frontiers
Many, if not all, post AGB stellar systems swiftly transition from a spherical to a powerful aspherical pre-planetary nebula (pPNE) outflow phase before waning into a PNe. The pPNe outflows require engine rotational energy and a mechanism to extract this energy into collimated outflows. Just radiation and rotation are insufficient but a symbiosis between rotation, differential rotation and larg...
متن کاملProtostellar Disk Dynamos and Hydromagnetic Outflows in Primordial Star Formation
Star formation occurs via accretion through a disk, which is likely to be turbulent, either because of gravitational or magnetorotational instability. Dynamo amplification of magnetic fields needs to be considered. As the disks are also stratified, the turbulence can be helical, with different signs of the helicity in each hemisphere. This provides a key ingredient for amplification of global s...
متن کاملThe Role of Thermal Conduction in Accretion Disks with Outflows
In this work we solve the set of hydrodynamical equations for accretion disks in the spherical coordinates (r,θ,ϕ) to obtain the explicit structure along θ direction. We study a two-dimensional advective accretion disc in the presence of thermal conduction. We find self-similar solutions for an axisymmetric, rotating, steady, viscous-resistive disk. We show that the global structure of an advec...
متن کامل