Very light magnetized jets on large scales – I. Evolution and magnetic fields

Magnetic fields, which are undoubtedly present in extragalactic jets and responsible for the observed synchrotron radiation, can affect the morphology and dynamics of the jets and their interaction with the ambient cluster medium. We examine the jet propagation, morphology and magnetic field structu...

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Vydáno v:Monthly notices of the Royal Astronomical Society Ročník 400; číslo 4; s. 1785 - 1802
Hlavní autoři: Gaibler, V., Krause, M., Camenzind, M.
Médium: Journal Article
Jazyk:angličtina
Vydáno: Oxford, UK Blackwell Publishing Ltd 21.12.2009
Wiley-Blackwell
Oxford University Press
Témata:
Astronomy
Earth, ocean, space
Exact sciences and technology
Fluid mechanics
galaxies: clusters: general
galaxies: jets
Magnetic fields
methods: numerical
MHD
Radio astronomy
radio continuum: galaxies
Stars & galaxies
MHD
galaxies: clusters: general
magnetic fields
galaxies: jets
methods: numerical
radio continuum: galaxies
Plasma
Magnetohydrodynamics
Eccentricity
Galaxies
Kelvin Helmholtz instability
Thermalization
Numerical method
Aspect ratio
Helical field
Continuum
Dynamics
Cosmic radio sources
Magnetic structure
Flux conservation
Synchrotron radiation
Mach number
Discontinuity
Turbulence
Extragalactic jet
Radio galaxies
Astrophysical jets
Galaxy clusters
Morphology
Models
Magnetic fields
ISSN:0035-8711, 1365-2966
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Popis
Shrnutí:Magnetic fields, which are undoubtedly present in extragalactic jets and responsible for the observed synchrotron radiation, can affect the morphology and dynamics of the jets and their interaction with the ambient cluster medium. We examine the jet propagation, morphology and magnetic field structure for a wide range of density contrasts, using a globally consistent setup for both the jet interaction and the magnetic field. The magnetohydrodynamic code nirvana is used to evolve the simulation, using the constrained transport method. The density contrasts are varied between η= 10−1 and 10−4 with constant sonic Mach number 6. The jets are supermagnetosonic and simulated bipolarly due to the low jet densities and their strong backflows. The helical magnetic field is largely confined to the jet, leaving the ambient medium non-magnetic. We find magnetic fields with plasma β∼ 10 already stabilize and widen the jet head. Furthermore, they are efficiently amplified by a shearing mechanism in the jet head and are strong enough to damp Kelvin–Helmholtz instabilities of the contact discontinuity. The cocoon magnetic fields are found to be stronger than expected from simple flux conservation and capable to produce smoother lobes, as found observationally. The bow shocks and jet lengths evolve self-similarly. The radio cocoon aspect ratios are generally higher for heavier jets and grow only slowly (roughly self-similar) while overpressured, but much faster when they approach pressure balance with the ambient medium. In this regime, self-similar models can no longer be applied. Bow shocks are found to be of low eccentricity for very light jets and have low Mach numbers. Cocoon turbulence and a dissolving bow shock create and excite waves and ripples in the ambient gas. Thermalization is found to be very efficient for low jet densities.
Bibliografie:istex:1095C24988C349EBA105EB533CF0F1744C671585
ark:/67375/HXZ-GMX26L9W-H
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ISSN:0035-8711
1365-2966
DOI:10.1111/j.1365-2966.2009.15625.x