All Figures

$\begin{figure} \par\resizebox{8.8cm}{!}{\includegraphics[clip]{3757f1.eps}} \end{figure}$ Figure 1: Example of power spectrum obtained for the He I 5876 line with the three datasets.
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In the text

$\begin{figure} \par\resizebox{8.8cm}{!}{\includegraphics[clip]{3757f2.eps}} \end{figure}$ Figure 2: Variations of the minimum intensity of the He I 4921 line observed in 1999 and the H $\beta$ line observed in 2001, folded in phase with f = 0.765 c d^-1 and with HJD ₀ = 2 451 499.0 and 2 452 262.6 respectively.
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In the text

$\begin{figure} \par\resizebox{8.8cm}{!}{\includegraphics[clip]{3757f3.eps}} \end{figure}$ Figure 3: Variations of the intensity of the V and R components of the He I 5876 line during the three observing runs. The data obtained in 2001 (in HJD minus 2 452 200) are plotted on the same time scale as the data obtained in 1998 (in HJD minus 2 451 100) and 1999 (in HJD minus 2 451 000) to make the comparison easier.
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In the text

$\begin{figure} \par\resizebox{8.8cm}{!}{\includegraphics[clip]{3757f4.eps}} \end{figure}$ Figure 4: Variations of the intensity of the V plus R components of the He I 5876, H $\alpha$ and H $\beta$ lines during the observations taken in 2001.
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In the text

$\begin{figure} \par\resizebox{8.8cm}{!}{\includegraphics[clip]{3757f5.eps}} \end{figure}$ Figure 5: Variations of the separation between the V and R peaks in the H $\beta$ line observed in 2001. Each of the five nights of observations is represented by a different symbol.
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In the text

$\begin{figure} \par\resizebox{8.8cm}{!}{\includegraphics[clip]{3757f6.eps}} \end{figure}$ Figure 6: Variations of the intensity of the V/R components of the He I 6678 line observed in 1999 and of the He I 5876 line during the observations taken in 1999 and 2001. The plots are folded in phase with f = 0.765 c d^-1 and with HJD ₀ = 2 451 499 and 2 452 262.6 respectively.
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In the text

$\begin{figure} \par\resizebox{8.8cm}{!}{\includegraphics[clip]{3757f7.eps}} \end{figure}$ Figure 7: Variations of the intensity of the V/R components of the H $\alpha$ and H $\beta$ lines observed in 2001. The plots are folded in phase with f = 0.765 c d^-1 and HJD ₀ = 2 452 262.6.
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In the text

$\begin{figure} \par\resizebox{18cm}{!}{\includegraphics[clip]{3757f8.ps}} \end{figure}$ Figure 8: Theoretical spectra (dots) compared to observations (solid line) from the Coralie spectrograph in the fitted spectral regions.
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In the text

$\begin{figure} \par\resizebox{8.8cm}{!}{\includegraphics[clip]{3757f9a.eps}}\par\resizebox{8.8cm}{!}{\includegraphics[clip]{3757f9b.eps}} \end{figure}$ Figure 9: Top panels: variation in the wind profiles of the UV C IV and Si IV lines; the fluxes are normalised to the mean spectrum. Bottom panels: variability signature, measuring the ratio of the observed variance (due to variability) to the expected variance (due to noise).
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In the text

$\begin{figure} \par\resizebox{8.8cm}{!}{\includegraphics[clip]{3757f10.eps}} \end{figure}$ Figure 10: Equivalent width variations (in Å) of the UV C IV and Si IV lines, folded in phase with the rotational period P = 1.286 d. The best fit is overplotted.
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In the text

$\begin{figure} \par\resizebox{8.8cm}{!}{\includegraphics[clip]{3757f11.eps}} \end{figure}$ Figure 11: Variations of the longitudinal component of the magnetic field, folded in phase with the period P = 1.29 d.
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In the text

$\begin{figure} \par\resizebox{18cm}{!}{\includegraphics[clip]{3757f12.ps}} \end{figure}$ Figure 12: Greyscale representation of the relative contribution of the magnetic dipole to the integrated longitudinal magnetic field on the visible hemisphere of $\omega$ Ori, at different rotational phases with step of $\delta \Phi = 0.125$ . The black color corresponds to positive field values and the white color to negative field values. The phase runs from the top left panel to the lower right panel and corresponds to the convention used in Fig. 11. A grid of magnetic longitudes and latitudes is overplotted, with the magnetic equator shown as a thicker black line. The rotation axis and equator are shown with a white cross and line respectively. Although the strongest magnetic field is at the magnetic poles, the positions on the stellar surface that contribute the most to the longitudinal field are not at the poles, due to a geometrical effect and to the limb darkening effect.
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In the text

$\begin{figure} \par\resizebox{8.8cm}{!}{\includegraphics[clip]{3757f13a.ps}}\resizebox{8.8cm}{!}{\includegraphics[clip]{3757f13b.ps}} \end{figure}$ Figure 13: Sketch of $\omega$ Ori. The wind flows from the magnetic poles to the magnetic equatorial plane, while the H $\alpha$ disk is in the rotation equatorial plane. The intersection regions of the two equators (EIR) are shown. The right- and left hand panels show the same geometrical configuration but half a rotation period apart. The dotted parallel on the stellar surface indicates the position of the magnetic axis as the star rotates. The positive pole is indicated with a cross when it is facing the observer.
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In the text

$\begin{figure} \par\resizebox{8.8cm}{!}{\includegraphics[clip]{3757f1.eps}} \end{figure}$	Figure 1: Example of power spectrum obtained for the He I 5876 line with the three datasets.
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$\begin{figure} \par\resizebox{8.8cm}{!}{\includegraphics[clip]{3757f2.eps}} \end{figure}$	Figure 2: Variations of the minimum intensity of the He I 4921 line observed in 1999 and the H $\beta$ line observed in 2001, folded in phase with f = 0.765 c d^-1 and with HJD ₀ = 2 451 499.0 and 2 452 262.6 respectively.
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$\begin{figure} \par\resizebox{8.8cm}{!}{\includegraphics[clip]{3757f3.eps}} \end{figure}$	Figure 3: Variations of the intensity of the V and R components of the He I 5876 line during the three observing runs. The data obtained in 2001 (in HJD minus 2 452 200) are plotted on the same time scale as the data obtained in 1998 (in HJD minus 2 451 100) and 1999 (in HJD minus 2 451 000) to make the comparison easier.
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$\begin{figure} \par\resizebox{8.8cm}{!}{\includegraphics[clip]{3757f4.eps}} \end{figure}$	Figure 4: Variations of the intensity of the V plus R components of the He I 5876, H $\alpha$ and H $\beta$ lines during the observations taken in 2001.
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$\begin{figure} \par\resizebox{8.8cm}{!}{\includegraphics[clip]{3757f5.eps}} \end{figure}$	Figure 5: Variations of the separation between the V and R peaks in the H $\beta$ line observed in 2001. Each of the five nights of observations is represented by a different symbol.
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$\begin{figure} \par\resizebox{8.8cm}{!}{\includegraphics[clip]{3757f6.eps}} \end{figure}$	Figure 6: Variations of the intensity of the V/R components of the He I 6678 line observed in 1999 and of the He I 5876 line during the observations taken in 1999 and 2001. The plots are folded in phase with f = 0.765 c d^-1 and with HJD ₀ = 2 451 499 and 2 452 262.6 respectively.
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$\begin{figure} \par\resizebox{8.8cm}{!}{\includegraphics[clip]{3757f7.eps}} \end{figure}$	Figure 7: Variations of the intensity of the V/R components of the H $\alpha$ and H $\beta$ lines observed in 2001. The plots are folded in phase with f = 0.765 c d^-1 and HJD ₀ = 2 452 262.6.
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$\begin{figure} \par\resizebox{18cm}{!}{\includegraphics[clip]{3757f8.ps}} \end{figure}$	Figure 8: Theoretical spectra (dots) compared to observations (solid line) from the Coralie spectrograph in the fitted spectral regions.
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$\begin{figure} \par\resizebox{8.8cm}{!}{\includegraphics[clip]{3757f9a.eps}}\par\resizebox{8.8cm}{!}{\includegraphics[clip]{3757f9b.eps}} \end{figure}$	Figure 9: Top panels: variation in the wind profiles of the UV C IV and Si IV lines; the fluxes are normalised to the mean spectrum. Bottom panels: variability signature, measuring the ratio of the observed variance (due to variability) to the expected variance (due to noise).
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$\begin{figure} \par\resizebox{8.8cm}{!}{\includegraphics[clip]{3757f10.eps}} \end{figure}$	Figure 10: Equivalent width variations (in Å) of the UV C IV and Si IV lines, folded in phase with the rotational period P = 1.286 d. The best fit is overplotted.
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$\begin{figure} \par\resizebox{8.8cm}{!}{\includegraphics[clip]{3757f11.eps}} \end{figure}$	Figure 11: Variations of the longitudinal component of the magnetic field, folded in phase with the period P = 1.29 d.
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