Astronomy & Astrophysics

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$\begin{figure} \par\includegraphics[width=14.3cm,clip]{0089Fig1.epsf}\end{figure}$ Figure 1: A schematic illustration of the jet-disk connection model. In the outer disk, $r\ge r_{{\rm tr}}$ , MFs are weak and advected around by fluid motion. Balbus-Hawley and Parker-instabilities in combination with reconnection and fast inwards fluid-motions amplify the MFs up to thermal equipartition at $r_{{\rm tr}}$ . Interior to $r_{{\rm tr}}$ , MFs become of large scale topology, strong, and start to suppress the generation of turbulence, turning the inflow into a turbulent-free plasma. In this case, torsional $\rm Alfv\acute{e}n$ waves become the dominant angular momentum carrier. They transport angular momentum from the disk upwards and form a super-Keplerian and dissipative layer, in which the plasma is virial-heated by reconnection of the TMF, hence start to centrifugally-accelerate outwards. Thus, the PMF in the equatorial layer is frozen into the plasma, and therefore is advected inwards together with the inflow. The transition layers sandwiching the inner part of the disk are dissipative. This allows the PMF to drift inwards through the plasma in the TL, thereby relaxing the winding-up problem of the PMF. Thus, the flow configuration may maintain stationarity, if the plasma in the TLs is resistive, whereas it is diffusion-free in the disk.
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In the text

$\begin{figure} \par\includegraphics[width=10.4cm,clip]{0089Fig3.ps}\end{figure}$ Figure 2: The profiles of the angular velocity in the innermost part of the disk and in the launching region. TAWs extract rotational energy from the disk-plasma efficiently and deposit it into the plasma adjusting to the disk-surface. As a consequence, the inflow adopts the sub-Keplerian profile $\Omega \sim r^{-5/4}$ in the disk-region, while the outflow adopts the super-Keplerian profile $\Omega \sim r^{-5/4}$ in the TL. Note that the up-stream boundary conditions determine whether the flow is sub- or super-Keplerian rotating.
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In the text

$\begin{figure} \par\includegraphics[width=7.5cm,clip]{0089Fig2.eps}\end{figure}$ Figure 3: The material fluxes governing an arbitrary volume cell in the TL are shown. $\theta _{{\rm W,d}}$ are latitudes that correspond to the locations of the interface between the disk and the TL, and to the upper surface of the TL, respectively. ${ F}^{\rm Z}_{{\rm in,out}}$ and ${ F}^{\rm R}_{{\rm in,out}}$ denote the material fluxes across the vertical and radial surfaces. The width of the cell is $H_{\rm W}$ , and the vertical material flux across $\theta _{\rm W}$ is set to vanish.
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In the text

$\begin{figure} \par\includegraphics[angle=-0,width=6.5cm,clip]{0089Fig4.eps}\end{figure}$ Figure 4: Possible configurations of converging and diverging poloidal magnetic field in the disk and in the TL. The left configuration corresponds to the case in which the magnetic pressure at the interface between the disk and the TL increases vertically, and therefore enhances the collapse of the TL. The right case corresponds to magnetic pressure that opposes collapse.
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In the text

$\begin{figure} \par\includegraphics[width=6.5cm,clip]{0089Fig5.eps} \includegra... ...p]{0089Fig6.eps}\par\includegraphics[width=6.5cm,clip]{0089Fig7.eps}\end{figure}$ Figure 5: A schematic description for a time-sequence of the angular velocity profile in the vertical direction. TAWs transport angular momentum vertically, enforcing the matter in the disk to rotate sub-Keplerian, and super-Keplerian in the TL ( top). The resulting $\Omega$ -profiles acquire negative and positive spatial derivatives ( middle), which in the presence of a large scale PMF, generate toroidal flux tubes of opposite signs ( bottom) that subsequently reconnect and annihilate.
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In the text

$\begin{figure} \par\includegraphics[width=6.5cm,clip]{0089Fig8.eps}\end{figure}$ Figure 6: The profiles of $\bar{\alpha}Re$ and $\log{Re}$ versus the magnetic Reynolds number Re, where $\bar{\alpha}= \alpha_{{\rm mag}} \left(\frac{B_{\rm T}}{B_{\rm p}}\right)$ . The intersection point $Re^{\rm c}$ corresponds to the solution of Eq. (14).
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In the text

$\begin{figure} \par\includegraphics[height=6.8cm,width=6.5cm,clip]{0089Fig9.ps}\end{figure}$ Figure 7: The radial profiles of the accretion rate in the disk region, and the outwards-oriented material flux in the launching layer, $F_{{\rm outflow}},$ which applies for $r \le r_{{\rm tr}}$ . Note that $F_{{\rm outflow}}$ vanishes at the inner boundary $r_{{\rm BL}}$ , where the effective gravity is set to vanish. Assuming $\epsilon =0.1=H_{\rm d}/r$ , the maximum material flux associated with the outflow is approximately 5% of the total accretion rate through the outer boundary. Thus, $F_{{\rm outflow}}$ depends on the disk temperature; colder disks yield lower $F_{{\rm outflow}}$ and vice versa.
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In the text

$\begin{figure} \par\includegraphics[width=16.2cm,clip]{0089Fig10.ps}\end{figure}$ Figure 8: The distribution of the velocity field in the transition region superposed on equally-spaced isolines of the angular velocity $\Omega$ . The strong decrease of $\Omega$ with radius in the equatorial region relative to its slow decrease in the TL is obvious. The overlying dynamically unstable corona is rotation-free. The orange colour corresponds to large material densities, violet to intermediate and blue corresponds to extremely tenuous coronal plasma. The 2D distributions of the variable have been obtained using a vertical interpolation procedure.
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In the text

$\begin{figure} \par\includegraphics[width=16.1cm,clip]{0089Fig11.ps}\end{figure}$ Figure 9: 20 equally-spaced isolines of the poloidal-component $B_{\rm P}$ (white contours), superposed on the coloured-distribution of the toroidal magnetic field. Blue, green and red colours correspond to low, intermediate and to high TMF-values, respectively.
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In the text

$\begin{figure} \par\includegraphics[angle=-0,width=6.5cm,clip]{0089Fig4.eps}\end{figure}$	Figure 4: Possible configurations of converging and diverging poloidal magnetic field in the disk and in the TL. The left configuration corresponds to the case in which the magnetic pressure at the interface between the disk and the TL increases vertically, and therefore enhances the collapse of the TL. The right case corresponds to magnetic pressure that opposes collapse.
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$\begin{figure} \par\includegraphics[width=6.5cm,clip]{0089Fig8.eps}\end{figure}$	Figure 6: The profiles of $\bar{\alpha}Re$ and $\log{Re}$ versus the magnetic Reynolds number Re, where $\bar{\alpha}= \alpha_{{\rm mag}} \left(\frac{B_{\rm T}}{B_{\rm p}}\right)$ . The intersection point $Re^{\rm c}$ corresponds to the solution of Eq. (14).
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$\begin{figure} \par\includegraphics[width=16.1cm,clip]{0089Fig11.ps}\end{figure}$	Figure 9: 20 equally-spaced isolines of the poloidal-component $B_{\rm P}$ (white contours), superposed on the coloured-distribution of the toroidal magnetic field. Blue, green and red colours correspond to low, intermediate and to high TMF-values, respectively.
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