1,122 research outputs found
Accretion-ejection instability in magnetized disks: Feeding the corona with Alfven waves
We present a detailed calculation of the mechanism by which the
Accretion-Ejection Instability can extract accretion energy and angular
momentum from a magnetized disk, and redirect them to its corona. In a disk
threaded by a poloidal magnetic field of the order of equipartition with the
gas pressure, the instability is composed of a spiral wave (analogous to
galactic ones) and a Rossby vortex. The mechanism detailed here describes how
the vortex, twisting the footpoints of field lines threading the disk,
generates Alfven waves propagating to the corona. We find that this is a very
efficient mechanism, providing to the corona (where it could feed a jet or a
wind) a substantial fraction of the accretion energy.Comment: accepted by A&
Accretion-Ejection Instability and a "Magnetic Flood" scenario for GRS 1915+105
We present an instability, occurring in the inner region of magnetized
accretion disks, which seems to be a good candidate to explain the
low-frequency QPO observed in many X-ray binaries. We then briefly show how, in
the remarkable case of the microquasar GRS 1915+105, identifying this QPO with
our instability leads to a scenario for the 30 mn cycles of this source.
In this scenario the cycles are controlled by the build-up of magnetic flux in
the disk.Comment: Proceedingd of the 5th Compton Symposium, Portsmouth, Sept. 199
Rossby Wave Instability and three-dimensional vortices in accretion disks
Context. The formation of vortices in accretion disks is of high interest in
various astrophysical contexts, in particular for planet formation or in the
disks of compact objects. But despite numerous attempts it has thus far not
been possible to produce strong vortices in fully three-dimensional simulations
of disks. Aims. The aim of this paper is to present the first 3D simulation of
a strong vortex, established across the vertically stratified structure of a
disk by the Rossby Wave Instability. Methods. Using the Versatile Advection
Code (VAC), we set up a fully 3D cylindrical stratified disk potentially prone
to the Rossby Wave Instability. Results. The simulation confirms the basic
expectations obtained from previous 2D analytic and numerical works. The
simulation exhibits a strong vortex that grows rapidly and saturates at a
finite amplitude. On the other hand the third dimension shows unexpected
additional behaviours that could be of strong importance in the astrophysical
roles that such vortices can play.Comment: Accepted by Astronomy and Astrophysic
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