All Figures

$\begin{figure} \par\includegraphics[width=7.7cm,clip]{4792f1.ps} \end{figure}$ Figure 1: Examples of our chromospheric models. The thick line is Kurucz' model for $\log(g) = 0.5$ and $T_{\rm eff}=4000$ K. Different models are shown with different line types for clarity.
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In the text

$\begin{figure} \par\includegraphics[width=7.7cm,clip]{4792f2.ps} \end{figure}$ Figure 2: Our chromospheric models: model A (solid line), for the least active stars, and model B (dashed line) for the most active stars (37872 and 47606). These models do not include any velocity field. The approximate depth of formation of the H $\alpha$ core and wings and of the Ca II K₂ and K₃ line components are also indicated.
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In the text

$\begin{figure} \par\includegraphics[width=8cm,clip]{4792f3.ps} \end{figure}$ Figure 3: The velocity as a function of depth (solid line), derived from the best match with the Ca K (innermost) and H $\alpha$ (outermost) lines, compared to the corresponding escape velocity (dashed line).
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In the text

$\begin{figure} \par\includegraphics[width=7.7cm,clip]{4792f4.ps} \end{figure}$ Figure 4: H $\alpha$ ( top panel) and Ca II K ( bottom panel) observed profiles (dotted lines) for the star 51499, compared with the computed profiles for our model A with no velocity (dashed lines) and with the velocity field shown in Fig. 3 (solid lines).
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In the text

$\begin{figure} \par\includegraphics[width=7.8cm,clip]{4792f5.ps} \end{figure}$ Figure 5: Same as in Fig. 4 for the star 48889.
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In the text

$\begin{figure} \par\includegraphics[width=7.8cm,clip]{4792f6.ps} \end{figure}$ Figure 6: Same as in Fig. 4 for the star 51454.
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In the text

$\begin{figure} \par\includegraphics[width=7.7cm,clip]{4792f7.ps} \end{figure}$ Figure 7: Same as in Fig. 4 for the star 47606. In this case we use model B.
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In the text

$\begin{figure} \par\includegraphics[width=7.7cm,clip]{4792f8.ps} \end{figure}$ Figure 8: Same as in Fig. 4 for the star 37872. In this case we use model B.
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In the text

$\begin{figure} \par\includegraphics[width=8cm,clip]{4792f9.ps} \end{figure}$ Figure 9: H $\alpha$ synthetic profiles computed for our model A (short-dashed line) and for a model with no chromosphere (long-dashed lines). The profile obtained by combining 90% of model A and 10% of the no-chromospheric model (solid line) gives a better fit to the observed profile of star 51499 (dotted line) than the purely chromospheric profile.
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In the text

$\begin{figure} \par\includegraphics[width=8cm,clip]{4792f10.ps} \end{figure}$ Figure 10: Log $\Phi$ , i.e. the total net radiative cooling rate, as a function of depth for our model A (thick line), and the most important contributions to it.
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In the text

$\begin{figure} \par\includegraphics[width=7.7cm,clip]{4792f1.ps} \end{figure}$	Figure 1: Examples of our chromospheric models. The thick line is Kurucz' model for $\log(g) = 0.5$ and $T_{\rm eff}=4000$ K. Different models are shown with different line types for clarity.
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$\begin{figure} \par\includegraphics[width=7.7cm,clip]{4792f2.ps} \end{figure}$	Figure 2: Our chromospheric models: model A (solid line), for the least active stars, and model B (dashed line) for the most active stars (37872 and 47606). These models do not include any velocity field. The approximate depth of formation of the H $\alpha$ core and wings and of the Ca II K₂ and K₃ line components are also indicated.
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$\begin{figure} \par\includegraphics[width=8cm,clip]{4792f3.ps} \end{figure}$	Figure 3: The velocity as a function of depth (solid line), derived from the best match with the Ca K (innermost) and H $\alpha$ (outermost) lines, compared to the corresponding escape velocity (dashed line).
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$\begin{figure} \par\includegraphics[width=7.7cm,clip]{4792f4.ps} \end{figure}$	Figure 4: H $\alpha$ ( top panel) and Ca II K ( bottom panel) observed profiles (dotted lines) for the star 51499, compared with the computed profiles for our model A with no velocity (dashed lines) and with the velocity field shown in Fig. 3 (solid lines).
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$\begin{figure} \par\includegraphics[width=7.8cm,clip]{4792f5.ps} \end{figure}$	Figure 5: Same as in Fig. 4 for the star 48889.
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$\begin{figure} \par\includegraphics[width=7.8cm,clip]{4792f6.ps} \end{figure}$	Figure 6: Same as in Fig. 4 for the star 51454.
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$\begin{figure} \par\includegraphics[width=7.7cm,clip]{4792f7.ps} \end{figure}$	Figure 7: Same as in Fig. 4 for the star 47606. In this case we use model B.
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$\begin{figure} \par\includegraphics[width=7.7cm,clip]{4792f8.ps} \end{figure}$	Figure 8: Same as in Fig. 4 for the star 37872. In this case we use model B.
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$\begin{figure} \par\includegraphics[width=8cm,clip]{4792f9.ps} \end{figure}$	Figure 9: H $\alpha$ synthetic profiles computed for our model A (short-dashed line) and for a model with no chromosphere (long-dashed lines). The profile obtained by combining 90% of model A and 10% of the no-chromospheric model (solid line) gives a better fit to the observed profile of star 51499 (dotted line) than the purely chromospheric profile.
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$\begin{figure} \par\includegraphics[width=8cm,clip]{4792f10.ps} \end{figure}$	Figure 10: Log $\Phi$ , i.e. the total net radiative cooling rate, as a function of depth for our model A (thick line), and the most important contributions to it.
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