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Structures magnétiques d'accrétion-éjection

Abstract : In both active galactic nuclei (AGN) and young stellar objects (YSOs), the common belief is growing that there is an interdependency between accretion onto a central objet and the highly collimated jets. This thesis deals with the investigation of the physical mechanism that leads to the formation of jets from a magnetized accretion disk. This has been performed by solving the complete set of magnetohydrodynamical equations describing such a structure. A resistive accretion disk is thread by open magnetic field lines, sheared by its rotation. The field lines brake the disk and extract both angular momentum and mechanical energy from it. A natural transition leads to the formation of a tenuous super-slow magnetosonic ideal jet. Stationarity is not fortuitous but should be achieved after sorne transient settlement of the structure, triggered by instabilites in the disk that give rise to anomalous transport coefficients. The overall structure is complex with an equipartition between magnetic and thermal energy densities, and components of the magnetic field of the same order of magnitude. We derive the observational signatures of such a disk, as weIl as the global energy budget and its consequences on the jets. Self-consistent solutions are displayed in the context of AGN and YSOs, in agreement with observations.
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Submitted on : Thursday, August 23, 2012 - 4:13:07 PM
Last modification on : Friday, November 6, 2020 - 4:05:30 AM
Long-term archiving on: : Saturday, November 24, 2012 - 2:40:52 AM


  • HAL Id : tel-00725026, version 1




Jonathan Ferreira. Structures magnétiques d'accrétion-éjection. Astrophysique galactique [astro-ph.GA]. Université Paris-Diderot - Paris VII, 1994. Français. ⟨tel-00725026⟩



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