Magnetized Accretion-Ejection Structures: 2.5-dimensional Magnetohydrodynamic Simulations of Continuous Ideal Jet Launching from Resistive Accretion Disks

By F. Casse, Rony Keppens. 2002

134 citations recorded by the source corpus.

We present numerical magnetohydrodynamic (MHD) simulations of a magnetized accretion disk launching trans-Alfvénic jets. These simulations, performed in a 2.5-dimensional time-dependent polytropic resistive MHD framework, model a resistive accretion disk threaded by an initial vertical magnetic field. The resistivity is only important inside the disk and is prescribed as η = αmVAH exp(-2Z2/H2), where VA stands for Alfvén speed, H is the disk scale height, and the coefficient αm is smaller than unity. By performing the simulations over several tens of dynamical disk timescales, we show that the launching of a collimated outflow occurs self-consistently and the ejection of matter is continuous and quasi-stationary. These are the first ever simulations of resistive accretion disks launching nontransient ideal MHD jets. Roughly 15% of accreted mass is persistently ejected. This outflow is safely characterized as a jet since the flow becomes superfast magnetosonic, well collimated, and reaches a quasi-stationary state. We present a complete illustration and explanation of the "accretion-ejection" mechanism that leads to jet formation from a magnetized accretion disk. In particular, the magnetic torque inside the disk brakes the matter azimuthally and allows for accretion, while it is responsible for an effective magnetocentrifugal acceleration in the jet. As such, the magnetic field channels the disk angular momentum and powers the jet acceleration and collimation. The jet originates from the inner disk region where equipartition between thermal and magnetic forces is achieved. A hollow, superfast magnetosonic shell of dense material is the natural outcome of the inward advection of a primordial field.

Subfields: Astronomy and Astrophysics

View Paper: https://www.semanticscholar.org/paper/38580041bc10be840ec746149a502908528d8af8

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In Astronomy and Astrophysics

Citations in the corpus

MHD simulations of jet acceleration from Keplerian accretion disks - The effects of disk resistivity (2007, methodology): “Isotropic resistive configurations (χm = 1) have been studied for two different values of the αm parameter: αm = 0.1 (simulation 1), which corresponds to the magnetic resistivity adopted by Casse & Keppens (2002, 2004), and αm = 1 (simulation 4).”
LOCAL STUDY OF ACCRETION DISKS WITH A STRONG VERTICAL MAGNETIC FIELD: MAGNETOROTATIONAL INSTABILITY AND DISK OUTFLOW (2012, background): “Numerous global simulations have studied launching of disk wind in the context of protostellar disks (e.g., Kato et al. 2002; Casse & Keppens 2002; Zanni et al. 2007)).”
Three-dimensional Magnetohydrodynamic Simulations of Radiatively Inefficient Accretion Flows (2003, background): “However, there are two important details in which the models of Hawley & Balbus (2002) differ from our simulations.”
WIND-DRIVEN ACCRETION IN PROTOPLANETARY DISKS. I. SUPPRESSION OF THE MAGNETOROTATIONAL INSTABILITY AND LAUNCHING OF THE MAGNETOCENTRIFUGAL WIND (2013, background): “…large diffusion (that is unjustified) to prevent rapid magnetic flux accumulation near the central object as mass accretes (Kato et al. 2002; Casse & Keppens 2002, 2004), and the resulting wind properties largely depend on the prescribed resistivity profile in the disk (Zanni et al. 2007).”