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

Abstract

We present numerical magnetohydrodynamic (MHD) simulations of a magnetized accretion disk launching trans-Alfve·nic 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 ield. The resistivity is only important inside the disk and is prescribed as … mVAH exp﷿ 2Z 2 =H 2 fi, where VA stands for Alfve·n speed, H is the disk scale height, and the coecien t m is smaller than unity. By performing the simulations over several tens of dynamical disk timescales, we show that the launching of a collimated outiow occurs self-consistently and the ejection of matter is continuous and quasi-stationary. These are the irst eversimulationsofresistiveaccretion disks launchingnontransient ideal MHD jets. Roughly15% ofaccreted mass is persistently ejected. This outiow is safely characterized as a jet since the iow becomes superfast magnetosonic, well collimated, and reaches a quasi-stationary state. We present a complete illustration and explanation of the eeaccretion-ejectionee 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 eecti ve magnetocentrifugal acceleration in the jet. As such, the magnetic ield 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 magnetosonicshellof densematerial isthenatural outcome of theinward advectionofaprimordial ield. Subject headings: accretion, accretion disks N galaxies:jets N ISM:jets and outiows N MHD