Mercredi 24 avril 2013, 14:30, salle de l'entresol

Outflows from turbulent accretion disks

MHD turbulence powered by the magnetorotational instability
is believed to be the main physical mechanism responsible for angular
momentum transport in accretion disks. Despite twenty years of
detailed studies of its properties, the saturation amplitude of the
turbulence is still not well constrained. In particular, the most
natural situation, a mean vertical magnetic field threading an
accretion disk, has only been extensively studied in homogeneous
situations thought to be relevant at the disk midplane. Such a
configuration precludes a detailed study of the interplay between MHD
turbulence and the jets that are observed to be launched by accretion
disks. I will show the results of recent numerical simulations that
investigate that interaction for the first time. I will make connexion
with classical disk wind theories, constrain the relative
importance between turbulent and outflow angular momentum
transport and highlight the limits of the approach currently
used. Finally, the special case of protoplanetary disks will be
discussed based on new results that recently appeared in the
literature.