Magnetic Collimation in PNe
نویسندگان
چکیده
Recent studies have focused on the the role of initially weak toroidal magnetic fields embedded in a stellar wind as the agent for collimation in planetary nebulae. In these models the wind is assumed to be permeated by a helical magnetic field in which the poloidal component falls off faster than the toroidal component. The collimation only occurs after the wind is shocked at large distances from the stellar source. In this paper we re-examine assumptions built into this “Magnetized Wind Blown Bubble” (MWBB) model. We show that a self-consistent study of the model leads to a large parameter regime where the wind is self-collimated before the shock wave is encountered. We also explore the relation between winds in the MWBB model and those which are produced via magneto-centrifugal processes. We conclude that a more detailed examination of the role of self-collimation is needed in the context of PNe studies. Subject headings: ISM: jets and outflows — magnetic fields — magnetohydrodynamics: MHD
منابع مشابه
The Formation of Collimated Outflows and Concentric Rings in Magnetized Planetary Nebulae
Magnetic fields and wind asymmetries from rotating stars, along with precession of the stellar rotation axis, can create most of the observed Planetary Nebulae morphologies and collimated outflows (jets). The collimation of the flows by magnetic tension becomes very efficient after the magnetized wind has passed through the reverse shock of the PN. Also, the concentric rings observed in some PN...
متن کاملMHD Disk Winds in PNe and pPNe
Winds from accretion disks have been proposed as the driving source for precessing jets and extreme bipolar morphologies in Planetary Nebulae (PNe) and proto-PNe (pPNe). Here we apply MHD disk wind models to PNe and pPNe by estimating separately the asymptotic MHD wind velocities and mass loss rates. We show that the resulting winds can recover the observed momentum and energy input rates for P...
متن کاملThe Kinematics of Point - Symmetric Planetary Nebulae : Observational Evidence of Precessing Outflows Mart́ın
The discovery of collimated outflows associated to point-symmetric features in Planetary Nebulae has proliferated in recent years. The systematic variation of radial velocity that many of them show strongly suggests a uniform rotation or precession of the ejection direction. Although several physical processes have been invoked, the formation mechanism of precessing collimated outflows in PNe i...
متن کاملOn the magnetic acceleration and collimation of astrophysical outflows
The axisymmetric 3-D MHD outflow of cold plasma from a magnetized and rotating astrophysical object is numerically simulated with the purpose of investigating the outflow’s magnetocentrifugal acceleration and eventual collimation. Gravity and thermal pressure are neglected while a split-monopole is used to describe the initial magnetic field configuration. It is found that the stationary final ...
متن کاملA Paradigm Lost : New Theories for Aspherical PNe
Theoretical Models for the shaping of PNe are reviewed in light of new high resolution images. The new data indicate the purely hydrodynamic interacting stellar winds model can not recover the full variety of shapes and kinematics. New models, some speculative, others more firmly grounded are discussed. In particular, accretion disks and magnetic fields are identified as two of the most promisi...
متن کامل