All Figures

$\begin{figure} \par\includegraphics[width=14.5cm,clip]{0471fig1.ps}\end{figure}$ Figure 1: Maps of physical quantities for a snapshot from the run with 200 G average vertical magnetic field. Upper left: vertical component of the magnetic field at the level $\tau =1$ at $500~{\rm nm}$ , corresponding to the visible solar surface. The image shows magnetic flux concentrations in the intergranular lanes. Upper right: vertical component of the velocity at the level $\tau =1$ at $500~{\rm nm}$ . Positive (negative) values correspond to downflows (upflows). Lower left: gas temperature on the level $\tau =1$ at 500 nm. There are local enhancements of the temperature in the regions of strong magnetic field in intergranular lanes. Lower right: normalized continuum intensity at 430 nm. The image shows brightenings in the magnetic flux concentrations, which closely correspond to the local temperature enhancements and magnetic flux concentrations.
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In the text

$\begin{figure} \par\includegraphics[width=14cm,clip]{0471fig2.ps}\end{figure}$ Figure 2: Spatially averaged spectra of Stokes I ( top) and Stokes V ( bottom) calculated for a snapshot from the run with 10 G average vertical magnetic field (thin lines). Atomic and molecular lines are indicated on the Stokes-I plot. The dashed line shows the shape of the filter function which is used for calculating the G-band intensity. The thick line in the upper panel shows the observed spectrum of the quiet Sun (Delbouille et al. 1973).
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In the text

$\begin{figure} \par\includegraphics[width=14.5cm,clip]{0471fig3.ps}\end{figure}$ Figure 3: Relation between normalized G-band brightness ( upper panels) and magnetic field strength at $\tau =1$ (500 nm, lower panels) for the snapshot from the 200-G run ( left side) and the 10-G run ( right side), respectively. While the simulated plage region (200-G run) shows many brightenings of magnetic features exceding the brightness of granules, there are only a few bright features in the simulated quiet region. Note the different grey-scales for the 200-G and the 10-G results, respectively.
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In the text

$\begin{figure} \includegraphics[width=15cm,clip]{0471fig4.ps}\end{figure}$ Figure 4: Scatter plots of G-band brightness vs. magnetic field strength (at $\log \tau=-1$ for 500 nm) for the 200-G run ( left) and for the 10-G run ( right). The brightness of the points with strong magnetic field exceeds that of the (weakly magnetized) granules in the 200-G case. The few flux concentrations in the 10-G case are smaller and weaker than the features shown by the 200-G case, and they do not exceed the brightness of the brightest granules.
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In the text

$\begin{figure} \par\includegraphics[width=14cm,clip]{0471fig5.ps}\end{figure}$ Figure 5: Scatter plots of G-band brightness vs. continuum brightness at 430 nm for the 200-G ( left) and 10-G ( right) runs. The slope of the distributions indicates a clear separation in two components corresponding to magnetic flux concentrations (|B|>500 G, gray dots) and weakly magnetized atmosphere (black dots), mainly corresponding to granules. In the 10-G case, the component corresponding to the magnetic flux concentrations is only weak, reflecting their small area fraction.
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In the text

$\begin{figure} \par\includegraphics[width=7.8cm,clip]{0471fig6.ps}\end{figure}$ Figure 6: Number density of CH molecules at the level $\log \tau=-1.0$ (500 nm) for the 200-G run. The dark regions with low CH concentration correspond to strong magnetic field concentrations and are cospatial with the brightenings on the G-band image (left part of Fig. 3).
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In the text

$\begin{figure} \par\includegraphics[width=7.8cm,clip]{0471fig7.ps}\end{figure}$ Figure 7: Scatter plot of the number density of CH molecules vs. magnetic field strength (both at $\log \tau=-1.0$ for $500~{\rm nm}$ ), calculated for the 200-G run.
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In the text

$\begin{figure} \par\includegraphics[width=13.8cm,clip]{0471fig8.ps} % \end{figure}$ Figure 8: The Stokes I spectra of a magnetic bright point ( top), a bright granule ( middle) and a non-magnetic intergranular dark point ( bottom). The spectra are normalized to the average continuum intensity at 430 nm. The CH lines are drastically weakened in the magnetic bright point, the remaining strong lines being atomic lines. Arrows indicate the CH line at 430.4383 nm, which is used as basis for Fig. 9.
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In the text

$\begin{figure} \par\includegraphics[width=12cm,clip]{0471fig9.ps}\end{figure}$ Figure 9: Temperature a), density b), magnetic field strength c) and number density of CH molecules d) as functions of geometrical depth for the average weakly magnetized atmosphere (mostly granules, $\vert B\vert<50~{\rm G}$ ; dot-dashed lines) and for the average atmosphere corresponding to magnetic bright points ( $\vert B\vert>1000~{\rm G}$ , ${I_G}/{\langle I_G \rangle} > 1.56$ ; solid lines). The diamonds and asterisks on the curves indicate the optical depth levels $\tau =2/3$ for the G-band continuum at 430 nm and for the center of the CH line at 430.4383 nm, respectively. z=0 corresponds to the $\tau =2/3$ level at the G-band continuum for the average weakly magnetized atmosphere. Owing to the lower CH abundance in the magnetic flux concentrations above $z \approx 0$ , the formation region of the CH lines is compressed in height and shifted geometrically downward to a region with larger temperature and smaller temperature gradient than outside. The resulting combination of larger continuum intensity and strongly weakened CH lines leads to a brightness enhancement in the G-band.
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In the text

$\begin{figure} \par\includegraphics[width=16.4cm,clip]{0471fi10.ps}\end{figure}$ Figure 10: Simulated and observed G-band images. Left: synthetic G-band image of the simulated area after spatial smoothing by the function mimicking the difraction by the telescope and the image degradation by the Earth's atmosphere. Right: observed G-band image with a similar area fraction of G-band bright points as in the 200-G simulation (subfield of an image taken with the Dutch Open Telescope on La Palma, courtesy: P. Sütterlin).
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In the text

$\begin{figure} \par\includegraphics[width=8cm,clip]{0471fi11.ps}\end{figure}$ Figure 11: Distribution functions of G-band brightness for the simulated (dash-dotted line), observed (dashed line), and smoothed simulated (solid line) images. The simulated image corresponds to the snapshot from the 200-G run.
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In the text

$\begin{figure} \par\includegraphics[width=14cm,clip]{0471fi12.ps}\end{figure}$ Figure 12: Scatter plots of normalized G-band versus continuum (432 nm) intensity for the synthetic (200-G run, left) and observed ( right) images. The plots show the separation in two components for both observed and simulated images. Grey dots on the plot for the simulated image correspond to the magnetic component ( $B>500~{\rm G}$ ).
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In the text

$\begin{figure} \par\includegraphics[width=7.8cm,clip]{0471fig6.ps}\end{figure}$	Figure 6: Number density of CH molecules at the level $\log \tau=-1.0$ (500 nm) for the 200-G run. The dark regions with low CH concentration correspond to strong magnetic field concentrations and are cospatial with the brightenings on the G-band image (left part of Fig. 3).
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$\begin{figure} \par\includegraphics[width=7.8cm,clip]{0471fig7.ps}\end{figure}$	Figure 7: Scatter plot of the number density of CH molecules vs. magnetic field strength (both at $\log \tau=-1.0$ for $500~{\rm nm}$ ), calculated for the 200-G run.
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$\begin{figure} \par\includegraphics[width=8cm,clip]{0471fi11.ps}\end{figure}$	Figure 11: Distribution functions of G-band brightness for the simulated (dash-dotted line), observed (dashed line), and smoothed simulated (solid line) images. The simulated image corresponds to the snapshot from the 200-G run.
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$\begin{figure} \par\includegraphics[width=14cm,clip]{0471fi12.ps}\end{figure}$	Figure 12: Scatter plots of normalized G-band versus continuum (432 nm) intensity for the synthetic (200-G run, left) and observed ( right) images. The plots show the separation in two components for both observed and simulated images. Grey dots on the plot for the simulated image correspond to the magnetic component ( $B>500~{\rm G}$ ).
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