Magnetic outflows from turbulent accretion disks: I. Vertical structure & secular evolution

Abstract

Astrophysical disks are likely embedded in an ambient vertical magnetic field. This ambient field is known to drive magneto-rotational turbulence in the disk bulk but is also responsible for the launching of magnetized outflows at the origin of astrophysical jets. The vertical structure and long-term (secular) evolution of such a system lack quantitative predictions. It is nevertheless this secular evolution that is proposed to explain time variability in many accreting systems such as X-ray binaries. We compute and analyze global 3D ideal-MHD simulations of an accretion disk threaded by a large-scale magnetic field. We evaluate the role of the turbulent terms in the equilibrium of the system. We then compute the transport of mass, angular momentum, and magnetic fields in the disk to characterize its secular evolution. We perform a parameter survey to characterize the influence of disk properties on secular transport. We find that weakly magnetized disks drive jets that carry away a small fraction of the disk angular momentum. The mass-weighted accretion speed remains subsonic although, there is always an upper turbulent atmospheric region where transonic accretion takes place. We show that a strongly magnetized version of the magneto-rotational instability drives this turbulence. The disk structure is drastically different from the conventional hydrostatic picture. The magnetic field is always dragged inwards in the disk, at a velocity that increases with the disk magnetization. Beyond a threshold on the latter, the disk undergoes a profound radial readjustment. It leads to the formation of an inner accretion-ejection region with a supersonic mass-weighted accretion speed and where the magnetic field distribution becomes steady, near equipartition with the thermal pressure. This inner structure shares many properties with the Jet Emitting Disk model described by Ferreira (1997).

Paper accepted on A&A, November 30, 2020

References in corpus (19)

• The NumPy array: a structure for efficient numerical computation
• PLUTO: a Numerical Code for Computational Astrophysics
• Which jet launching mechanism(s) in TTauri stars?
• Global simulations of protoplanetary disks with ohmic resistivity and ambipolar diffusion
• Angular Momentum Transport in Accretion Disks: Scaling Laws in MRI-driven Turbulence
• Advection of Magnetic Fields in Accretion Disks: Not So Difficult After All
• Magnetic Flux Concentration and Zonal Flows in Magnetorotational Instability Turbulence
• ALMA discovery of a rotating SO/SO${}_2$ flow in HH212. A possible MHD disk wind?
• Strong disc winds traced throughout outbursts in black-hole X-ray binaries
• ALMA reveals a large structured disk and nested rotating outflows in DG Tau B
• Global Hydromagnetic Simulations of Protoplanetary Disks with Stellar Irradiation and Simplified Thermochemistry
• Spontaneous ring formation in wind-emitting accretion discs
• Global evolution of the magnetic field in a thin disc and its consequences for protoplanetary systems
• Magnetically-driven jets and winds from weakly magnetized accretion disks
• Coronae and Winds from Irradiated Disks in X-ray binaries
• A Resolution Study of Magnetically Arrested Disks
• A unified accretion-ejection paradigm for black hole X-ray binaries. IV. Replication of the 2010--2011 activity cycle of GX 339-4
• Wind-driven Accretion in Transitional Protostellar Disks
• Magnetic field transport in compact binaries

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• Absorption lines from magnetically driven winds in X-ray binaries II: high resolution observational signatures expected from future X-ray observatories
• Angular momentum transport and thermal stabilization of optically thin, advective accretion flows through large-scale magnetic fields