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Magnetocentrifugal Launching of Jets from Accretion Disks. I. Cold Axisymmetric Flows

Krasnopolsky, Ruben and Li, Zhi-Yun and Blandford, Roger (1999) Magnetocentrifugal Launching of Jets from Accretion Disks. I. Cold Axisymmetric Flows. Astrophysical Journal, 526 (2). pp. 631-642. ISSN 0004-637X. doi:10.1086/308023.

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We present time-dependent, numerical simulations of the magnetocentrifugal model for jet formation, in an axisymmetric geometry, using a modification of the ZEUS3D code adapted to parallel computers. The gas is supposed cold with negligible thermal pressure throughout. The number of boundary conditions imposed on the disk surface is that necessary and sufficient to take into account information propagating upstream from the fast and Alfvén critical surfaces, avoiding overdetermination of the flow and unphysical effects, such as numerical "boundary layers" that otherwise isolate the disk from the flow and produce impulsive accelerations. It is known that open magnetic field lines can either trap or propel the gas, depending upon the inclination angle, θ, of the poloidal field to the disk normal. This inclination is free to adjust, changing from trapping to propelling when θ is larger than θ_c ~ 30°; however, the ejected mass flux is imposed in these simulations as a function of the radius alone. As there is a region, near the origin, where the inclination of field lines to the axis is too small to drive a centrifugal wind, we inject a thin, axial jet, expected to form electromagnetically near black holes in active galactic nuclei and Galactic superluminal sources. Rapid acceleration and collimation of the flow is generally observed when the disk field configuration is propelling. We parameterize our runs using a magnetic flux Ψ ∝ R^(-eΨ) and mass flux j = ρv_z ∝ R^(-ej). We show in detail the steady state of a reference run with parameters e_Ψ = -1/2, e_j = 3/2, finding that the wind leaves the computational volume in the axial direction with an Alfvén number M_A ~ 4, poloidal speed v_p ~ 1.6v_(K0), collimated inside an angle θ ~ 11°. We show also the thrust T, energy L, torque G, and mass discharge Ṁ of the outgoing wind, and we illustrate the dependence of these quantities with the exponents e_Ψ and e_j.

Item Type:Article
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URLURL TypeDescription Paper
Blandford, Roger0000-0002-1854-5506
Additional Information:© 1999. The American Astronomical Society. Received 1999 February 15; accepted 1999 July 19. This research was performed in part using the CACR parallel computer system operated by Caltech. We acknowledge useful discussions with James Stone, John Hawley, David Meier, and Shinji Koide. This research was supported by NSF grant AST 95-29170 and NASA grant 5-2837. R. B. thanks John Bahcall for hospitality at the Institute for Advanced Study and the Beverly and Raymond Sackler Foundation for support at the Institute of Astronomy.
Funding AgencyGrant Number
NSFAST 95-29170
Beverly and Raymond Sackler FoundationUNSPECIFIED
Subject Keywords:galaxies: active; ISM: jets and outflows; methods: numerical; MHD
Issue or Number:2
Record Number:CaltechAUTHORS:20170408-140550061
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Official Citation:Ruben Krasnopolsky et al 1999 ApJ 526 631
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:75918
Deposited By: 1Science Import
Deposited On:19 Apr 2017 19:46
Last Modified:15 Nov 2021 16:56

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