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Numerical simulations of winds driven by radiation force from the corona above a thin disk
Observations show that winds can be driven from the innermost region (inside
a 50 Schwarschild radius) of a thin disk. It is interesting to study the winds
launched from the innermost region. A hot corona above the black hole (BH) thin
disk is irradiated by the disk. We perform two-dimensional hydrodynamical
simulations to study the winds driven by radiation force from the corona in the
innermost regions. The hard X-ray spectrum from active galactic nuclei (AGNs)
suggests that the corona temperature is about K, so that we mainly
analyze the properties of winds (or outflows) from the K corona. The
disk luminosity plays an important role in driving the outflows. The more
luminous the disk, the stronger the outflows. Mass outflow rate () at a 90 Schwarschild radius depends on disk luminosity, which can be
described as ( is the ratio
of the disk luminosity to the Eddington luminosity). In the case of high
luminosity (e.g. ), the supersonic outflows with maximum speed
Km s are launched at -- and
-- away from the pole axis. The Bernoulli parameter keeps
increasing with the outward propagation of outflows. The radiation force keeps
accelerating the outflows when outflows move outward. Therefore, we can expect
the outflows to escape from the BH gravity and go to the galactic scale. The
interaction between outflows and interstellar medium may be an important AGN
feedback process.Comment: 9 pages, 12 figures, accepted for publication in Ap
Two dimensional numerical simulations of Supercritical Accretion Flows revisited
We study the dynamics of super-Eddington accretion flows by performing
two-dimensional radiation-hydrodynamic simulations. Compared with previous
works, in this paper we include the component of the viscous
stress and consider various values of the viscous parameter . We find
that when is included, the rotational speed of the
high-latitude flow decreases, while the density increases and decreases at the
high and low latitudes, respectively. We calculate the radial profiles of
inflow and outflow rates. We find that the inflow rate decreases inward,
following a power law form of . The value of
depends on the magnitude of and is within the range of .
Correspondingly, the radial profile of density becomes flatter compared with
the case of a constant . We find that the density profile can be
described by , and the value of is almost same for a
wide range of ranging from to . The inward
decrease of inflow accretion rate is very similar to hot accretion flows, which
is attributed to the mass loss in outflows. To study the origin of outflow, we
analyze the convective stability of slim disk. We find that depending on the
value of , the flow is marginally stable (when is small) or
unstable (when is large). This is different from the case of
hydrodynamical hot accretion flow where radiation is dynamically unimportant
and the flow is always convectively unstable. We speculate that the reason for
the difference is because radiation can stabilize convection. The origin of
outflow is thus likely because of the joint function of convection and
radiation, but further investigation is required.Comment: 16 pages, 13 figures, accepted for publication in Ap
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