Black hole magnetosphere with small scale flux tubes–II. Stability and dynamics

Kavli Affiliate: Roger D. Blandford

| First 5 Authors: Yajie Yuan, Anatoly Spitkovsky, Roger D. Blandford, Dan R. Wilkins,

| Summary:

In some Seyfert Galaxies, the hard X-rays that produce fluorescent emission
lines are thought to be generated in a hot corona that is compact and located
at only a few gravitational radii above the supermassive black hole. We
consider the possibility that this X-ray source may be powered by small scale
magnetic flux tubes attached to the accretion disk near the black hole. We use
three dimensional, time dependent force-free simulations in a simplified
setting to study the dynamics of such flux tubes as they get continuously
twisted by the central compact star/black hole. We find that, the dynamical
evolution of the flux tubes connecting the central compact object and the
accretion disk is strongly influenced by the confinement of the surrounding
field. Although differential rotation between the central object and the disk
tends to inflate the flux tubes, strong confinement from surrounding field
quenches the formation of a jet-like outflow, as the inflated flux tube becomes
kink unstable and dissipates most of the extracted rotational energy relatively
close to the central object. Such a process may be able to heat up the plasma
and produce strong X-ray emission. We estimate the energy dissipation rate and
discuss its astrophysical implications.

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