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- Mami Machida
- 2002

We present the results of three-dimensional global resistive magnetohydrodynamic (MHD) simulations of black hole accretion flows. General relativistic effects are simulated by using the pseudo-Newtonian potential. Initial state is an equilibrium model of a torus threaded by weak toroidal magnetic fields. As the magnetorotational instability (MRI) grows in… (More)

We carried out global three-dimensional resistive magnetohydrodynamic simulations of galactic gaseous disks to investigate how the galactic magnetic fields are amplified and maintained. We adopt a steady axisymmetric gravitational potential given by Miyamoto & Nagai (1975) and Miyamoto, Satoh & Ohashi (1980). As the initial condition, we assume a warm (T ∼… (More)

We carried out three-dimensional global resistive magnetohydrodynamic (MHD) simulations of the cooling instability in optically thin hot black hole accretion flows by assuming bremsstrahlung cooling. General relativistic effects are simulated by using the pseudo-Newtonian potential. Cooling instability grows when the density of the accretion disk becomes… (More)

- Yasuo Fukui, Hiroaki Yamamoto, +11 authors Akira Mizuno
- Science
- 2006

The central few hundred parsecs of the Milky Way host a massive black hole and exhibit very violent gas motion and high temperatures in molecular gas. The origin of these properties has been a mystery for the past four decades. Wide-field imaging of the (12)CO (rotational quantum number J = 1 to 0) 2.6-millimeter spectrum has revealed huge loops of dense… (More)

We construct a new family of analytic models of black hole accretion disks in dynamical equilibria. Our construction is based on assuming distributions of angular momentum and entropy. For a particular choice of the distribution of angular momentum, we calculate the shapes of equipressure surfaces. The equipressure surfaces we find are similar to those in… (More)

- Kunio T. Takahashi, Satoshi Nozawa, +5 authors Hiroaki Yamamoto
- 2009

We carried out two-dimensional magnetohydrodynamic simulations of the Galactic gas disk to show that the dense loop-like structures discovered by the Galactic center molecular cloud survey by NANTEN 4 m telescope can be formed by the buoyant rise of magnetic loops due to the Parker instability. At the initial state, we assumed a gravitationally stratified… (More)

- Mami Machida, Ryoji Matsumoto, +7 authors Kohji Tomisaka
- 2000

A survey for the molecular clouds in the Galaxy with NANTEN mm telescope has discovered molecular loops in the Galactic center region. The loops show monotonic gradients of the line of sight velocity along the loops and the large velocity dispersions towards their foot points. It is suggested that these loops are explained in terms of the buoyant rise of… (More)

- Mami Machida
- 2003

Outflows and convective motions in accretion flows have been intensively discussed recently in the context of advection-dominated accretion flow (ADAF) based on two-dimensional (2D) and three-dimensional (3D) hydrodynamical simulations. We, however, point that without proper treatments of the disk magnetic fields, a major source of viscosity, one can never… (More)

We present the results of global three dimensional magneto-hydrodynamic simulations of black hole accretion flows. We focus on the dependence of numerical results on the gas temperature Tout supplied from the outer region. General relativistic effects are taken into account using the pseudo-Newtonian potential. We ignore the radiative cooling of the… (More)