All Figures

$\begin{figure} \par\includegraphics[width=5.5cm,clip]{5192fig1.ps}\end{figure}$ Figure 1: Contour lines of the toroidal magnetic field strength of the imposed axisymmetric magnetic field if q=2 with a positive $B_\phi$ in the northern hemisphere and a negative one in the southern hemisphere.
Open with DEXTER

In the text

$\begin{figure} \par\includegraphics[width=7.65cm,clip]{5192fig2.ps}\end{figure}$ Figure 2: Lines of marginal stability in a rigidly rotating sphere for different symmetries of the m=1 mode with respect to the equator. The solid line is for the solution with a symmetric velocity field; the dotted line is for the antisymmetric velocity field. The magnetic Prandtl number was unity.
Open with DEXTER

In the text

$\begin{figure} \par\includegraphics[width=7.65cm,clip]{5192fig3.ps}\end{figure}$ Figure 3: Lines of marginal stability in a rigidly rotating sphere for various values of the magnetic Prandtl number Pm.
Open with DEXTER

In the text

$\begin{figure} \par\includegraphics[width=8.5cm,clip]{5192fig4.ps}\end{figure}$ Figure 4: Magnetic-field perturbation growing in a rigidly rotating sphere at a magnetic Reynolds number of ${\rm Rm}=10~000$ and a (supercritical) Lundquist number of S=2000. The grey scale represents $b_\phi$ (without the background profile $B_\phi$ of (5), and the arrows are the field vectors projected on the meridional section.
Open with DEXTER

In the text

$\begin{figure} \par\includegraphics[width=7.65cm,clip]{5192fig5.ps}\end{figure}$ Figure 5: Lines of marginal stability in a rigidly rotating sphere as in Fig. 3, but with the flow restricted to toroidal motions.
Open with DEXTER

In the text

$\begin{figure} \par\includegraphics[width=8cm,clip]{5192fig6.ps}\end{figure}$ Figure 6: Critical magnetic-field strengths as a function of the thickness of the field belts. The values were derived for the symmetric m=1 mode at ${\rm Rm}=5000$ and ${\rm Pm}=1$ .
Open with DEXTER

In the text

$\begin{figure} \par\includegraphics[width=7.6cm,clip]{5192fig7.ps}\end{figure}$ Figure 7: Lines of marginal stability for toroidal magnetic field belts in a differentially rotating spherical shell with $\Omega \sim (1-\alpha\cos^2\theta)$ . The value of $\alpha$ is given on the vertical axis. The magnetic Reynolds number of these computations was fixed at ${\rm Rm}=1000$ for the solid line and at ${\rm Rm}=10~000$ for the dotted line.
Open with DEXTER

In the text

$\begin{figure} \par\includegraphics[width=7.6cm,clip]{5192fig8.ps}\end{figure}$ Figure 8: Lines of marginal stability for toroidal magnetic field belts (q=2) in a differentially rotating spherical shell at a magnetic Reynolds number of ${\rm Rm}=10~000$ . The values at the vertical axis are $\alpha$ from (10). The dashed line shows the marginal stability of a horizontal flow, whereas the solid line is the stability limit for full toroidal and poloidal flow.
Open with DEXTER

In the text

$\begin{figure} \par\includegraphics[width=8cm,clip]{5192fig9.ps}\end{figure}$ Figure 9: The same graph as in Fig. 3 but for the full differential rotation profile $\Omega (r,\theta )$ and ${\rm Pm}=1$ . The slope of this full problem is now $\zeta = 0.66$ .
Open with DEXTER

In the text

$\begin{figure} \par\includegraphics[width=7.65cm,clip]{5192fg10.ps}\end{figure}$ Figure 10: Lines of marginal stability for thin toroidal magnetic field belts (q=4) in a differentially rotating spherical shell at a magnetic Reynolds number of ${\rm Rm}=10~000$ . As in Fig. 8, the dashed line is for a horizontal flow, whereas the solid line is for the full toroidal and poloidal flows.
Open with DEXTER

In the text

$\begin{figure} \par\includegraphics[width=8.5cm,clip]{nonlin_modes.ps}\end{figure}$ Figure 11: Nonlinear evolution of various azimuthal modes with time. The individual lines refer to the modes m=0 to m=8, from top to bottom. The background $\Omega$ -profile is kept constant in this computation.
Open with DEXTER

In the text

$\begin{figure} \par\includegraphics[width=5.5cm,clip]{5192fig1.ps}\end{figure}$	Figure 1: Contour lines of the toroidal magnetic field strength of the imposed axisymmetric magnetic field if q=2 with a positive $B_\phi$ in the northern hemisphere and a negative one in the southern hemisphere.
Open with DEXTER

$\begin{figure} \par\includegraphics[width=7.65cm,clip]{5192fig2.ps}\end{figure}$	Figure 2: Lines of marginal stability in a rigidly rotating sphere for different symmetries of the m=1 mode with respect to the equator. The solid line is for the solution with a symmetric velocity field; the dotted line is for the antisymmetric velocity field. The magnetic Prandtl number was unity.
Open with DEXTER

$\begin{figure} \par\includegraphics[width=7.65cm,clip]{5192fig3.ps}\end{figure}$	Figure 3: Lines of marginal stability in a rigidly rotating sphere for various values of the magnetic Prandtl number Pm.
Open with DEXTER

$\begin{figure} \par\includegraphics[width=8.5cm,clip]{5192fig4.ps}\end{figure}$	Figure 4: Magnetic-field perturbation growing in a rigidly rotating sphere at a magnetic Reynolds number of ${\rm Rm}=10~000$ and a (supercritical) Lundquist number of S=2000. The grey scale represents $b_\phi$ (without the background profile $B_\phi$ of (5), and the arrows are the field vectors projected on the meridional section.
Open with DEXTER

$\begin{figure} \par\includegraphics[width=7.65cm,clip]{5192fig5.ps}\end{figure}$	Figure 5: Lines of marginal stability in a rigidly rotating sphere as in Fig. 3, but with the flow restricted to toroidal motions.
Open with DEXTER

$\begin{figure} \par\includegraphics[width=8cm,clip]{5192fig6.ps}\end{figure}$	Figure 6: Critical magnetic-field strengths as a function of the thickness of the field belts. The values were derived for the symmetric m=1 mode at ${\rm Rm}=5000$ and ${\rm Pm}=1$ .
Open with DEXTER

$\begin{figure} \par\includegraphics[width=7.6cm,clip]{5192fig7.ps}\end{figure}$	Figure 7: Lines of marginal stability for toroidal magnetic field belts in a differentially rotating spherical shell with $\Omega \sim (1-\alpha\cos^2\theta)$ . The value of $\alpha$ is given on the vertical axis. The magnetic Reynolds number of these computations was fixed at ${\rm Rm}=1000$ for the solid line and at ${\rm Rm}=10~000$ for the dotted line.
Open with DEXTER

$\begin{figure} \par\includegraphics[width=7.6cm,clip]{5192fig8.ps}\end{figure}$	Figure 8: Lines of marginal stability for toroidal magnetic field belts (q=2) in a differentially rotating spherical shell at a magnetic Reynolds number of ${\rm Rm}=10~000$ . The values at the vertical axis are $\alpha$ from (10). The dashed line shows the marginal stability of a horizontal flow, whereas the solid line is the stability limit for full toroidal and poloidal flow.
Open with DEXTER

$\begin{figure} \par\includegraphics[width=8cm,clip]{5192fig9.ps}\end{figure}$	Figure 9: The same graph as in Fig. 3 but for the full differential rotation profile $\Omega (r,\theta )$ and ${\rm Pm}=1$ . The slope of this full problem is now $\zeta = 0.66$ .
Open with DEXTER

$\begin{figure} \par\includegraphics[width=7.65cm,clip]{5192fg10.ps}\end{figure}$	Figure 10: Lines of marginal stability for thin toroidal magnetic field belts (q=4) in a differentially rotating spherical shell at a magnetic Reynolds number of ${\rm Rm}=10~000$ . As in Fig. 8, the dashed line is for a horizontal flow, whereas the solid line is for the full toroidal and poloidal flows.
Open with DEXTER

$\begin{figure} \par\includegraphics[width=8.5cm,clip]{nonlin_modes.ps}\end{figure}$	Figure 11: Nonlinear evolution of various azimuthal modes with time. The individual lines refer to the modes m=0 to m=8, from top to bottom. The background $\Omega$ -profile is kept constant in this computation.
Open with DEXTER