Magnetized Accretion‐Ejection Structures: 2.5‐dimensional Magnetohydrodynamic Simulations of Continuous Ideal Jet Launching from Resistive Accretion Disks
- 20 December 2002
- journal article
- Published by American Astronomical Society in The Astrophysical Journal
- Vol. 581 (2), 988-1001
- https://doi.org/10.1086/344340
Abstract
We present numerical magnetohydrodynamic (MHD) simulations of a magnetized accretion disk launching trans-Alfvenic 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 eta = alpha_m V_AH exp(-2Z^2/H^2), where V_A stands for Alfven speed, H is the disk scale height and the coefficient alpha_m 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 non-transient ideal MHD jets. Roughly 15% of accreted mass is persistently ejected. This outflow is safely characterized as a jet since the flow becomes super-fastmagnetosonic, 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 magneto-centrifugal 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, super-fastmagnetosonic shell of dense material is the natural outcome of the inwards advection of a primordial field.Comment: ApJ (in press), 32 pages, Higher quality version available at http://www-laog.obs.ujf-grenoble.fr/~fcassKeywords
This publication has 30 references indexed in Scilit:
- 2.5‐dimensional Nonsteady Magnetohydrodynamic Simulations of Magnetically Driven Jets from Geometrically Thin DisksThe Astrophysical Journal, 2002
- Atomic T Tauri disk winds heated by ambipolar diffusionAstronomy & Astrophysics, 2001
- Evidence for a Disk-Jet Interaction in the Microquasar GRS 1915+105The Astrophysical Journal, 1998
- Instability, turbulence, and enhanced transport in accretion disksReviews of Modern Physics, 1998
- Disk Accretion and Mass Loss from Young StarsThe Astrophysical Journal, 1995
- Forbidden-line emission and infrared excesses in T Tauri stars - Evidence for accretion-driven mass loss?The Astrophysical Journal, 1990
- The collimation of magnetized windsThe Astrophysical Journal, 1989
- Hydromagnetic flows from accretion discs and the production of radio jetsMonthly Notices of the Royal Astronomical Society, 1982
- The Effect of Nonzero ∇ · B on the numerical solution of the magnetohydrodynamic equationsJournal of Computational Physics, 1980
- Accretion Disc Electrodynamics -- A Model for Double Radio SourcesMonthly Notices of the Royal Astronomical Society, 1976