Magnetized accretion-ejection structures IV. Magnetically-driven jets from resistive, viscous, Keplerian discs

摘要

We present steady-state calculations of self-similar magnetized accretiondiscs driving cold, adiabatic, non-relativistic jets. For the first time, boththe magnetic torque due to the jets and a turbulent "viscous" torque are takeninto account. This latter torque allows a dissipation of the accretion power asradiation at the disc surfaces, while the former predominantly provides jetswith power. The parameter space of these structures has been explored. It ischaracterized by four free parameters, namely the disc aspect ratio and threeMHD turbulence parameters, related to the anomalous magnetic diffusivities andviscosity. It turns out that launching cold jets from thin, dissipative discsimplies anisotropic turbulent dissipation. Jets that asymptotically reach ahigh Alfvenic Mach number are only produced by weakly dissipative discs. We obtained general analytical relations between disc and jet quantities thatmust be fulfilled by any steady-state model of cold jets, launched from a largeradial extension of thin discs. We also show that such discs cannot have adominant viscous torque. This is because of the chosen geometry, imposing thelocus of the Alfven surface. Some observational consequences of these cold magnetized accretion-ejectionstructures are also briefly discussed.