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Astron. Astrophys. 361, 1178-1190 (2000)


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Magnetized accretion-ejection structures

V. Effects of entropy generation inside the disc

F. Casse and J. Ferreira

Laboratoire d'Astrophysique de l'Observatoire de Grenoble, B.P.53, 38041 Grenoble cedex 9, France

Received 28 April 2000 / Accepted 26 July 2000

Abstract

In this paper, steady-state MHD calculations of non-relativistic magnetized accretion discs driving jets are presented. For the first time, an energy equation describing the effects of entropy generation along streamlines is included. Using a simplified approach, we showed that thermal effects have a tremendous influence on the disc capability to feed jets with mass.

The disc ejection efficiency is measured by the parameter [FORMULA], where [FORMULA] is the local disc accretion rate. While previous self-similar solutions were only able to produce jets with [FORMULA], solutions with a coronal heating display huge efficiencies up to [FORMULA]. Moreover, taking thermal effects into account allows one to obtain both fast and slow magnetic rotators.

Since most of the jet properties (like asymptotic velocity or degree of collimation) depend on the mass load, it arises from this study that any quantitative result requires a detailed analysis of the disc energetics.

Key words: accretion, accretion disks – Magnetohydrodynamics (MHD) – stars: formation – ISM: jets and outflows – galaxies: nuclei – galaxies: jets

Send offprint requests to: Fabien.Casse@obs.ujf-grenoble.fr

© European Southern Observatory (ESO) 2000

Online publication: October 10, 2000

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