All Figures

$\begin{figure} \mbox{\hspace{2.6cm} $I$\space \hspace{3.2cm} $\sqrt{Q^2+U^2}/I$\... ...box{$^\circ$ }) \hspace{4.3cm} $V/I$ , $\chi/45\hbox{$^\circ$ }$ }\end{figure}$ Figure 1: Colour plots of polarimetric subpulse patterns, pulse number (ordinate) versus pulse longitude (abscissa). The top row shows a sequence of single pulses PSR B0809+74 at 328 MHz, after Ramachandran et al. (2002) but now correctly calibrated. The other rows show mean drift bands, produced by folding the Stokes parameters modulo subpulse modulation period, and plotted twice for continuity. From top to bottom: PSR B0809+74 at 328 MHz, PSR B0320+39 at 357 MHz and PSR B0818-13 at 328 MHz. In the folded plots, a parameterisation of the polarization that splits it into intensity ( $\vert\vec{p}\vert$ ) and orientation (position angle, $\vert\psi \vert$ and ellipticity angle, $\chi=\frac{1}{2}\tan^{-1} V/(Q^2+U^2)^{1/2}$ : see footnote to Sect. 3.1.1) are used to better assess consistency with OPMs. The colour scales used are shown at the bottom. Intensity parameters (left colour scale) are normalised by the peak value plotted in a given panel.
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In the text

$\begin{figure} \begin{tabular}{@{\extracolsep{-5mm}}ccc} \hspace{8mm} PSR B0809+... ...}} & \resizebox{5cm}{!}{\includegraphics{1029f2c.eps}}\end{tabular} \end{figure}$ Figure 2: Polarization histograms. The top panel shows the total intensity (solid) and polarized intensity (dotted) of the average pulse profile. The centre panel shows the longitude-dependent histogram of position angle (plotted twice for continuity) along with the position angle of the mean profile. The bottom panel shows the histogram of $\sin$ $2\chi$ (where $\chi$ is the ellipticity angle), along with its counterpart from the mean profile. ( $\sin$ $2\chi$ is chosen over $\chi$ so that each bin samples an equal area of the Poincaré sphere; see Edwards & Stappers 2004.) For convenience the scale is drawn (non-linearly) in terms of $\chi$ . Only samples with a polarized intensity greater than three times the RMS noise (estimated from the off-pulse) were included. The density scale is such that bins containing no samples are white, while other values are mapped linearly from medium grey to black.
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In the text

$\begin{figure} \par\begin{tabular}{@{\extracolsep{-2mm}}cccc} \hspace{7mm}PSR B0... ...} & \resizebox{!}{10cm}{\includegraphics{1029f3d.eps}}\end{tabular} \end{figure}$ Figure 3: Results of eigenanalysis of the covariance matrices. The top panel shows the average intensity profile (thick solid line), the square roots of the eigenvalues (solid, dashed, dotted thin lines, in descending order of value), and the polarization entropy (thick dotted line). The middle panel shows the position angle of the mean polarization vector (thick line, plotted repeatedly at offsets of $180\hbox {$^\circ $ }$ for continuity) and of the first eigenvector (thin line, plotted repeatedly at offsets of $90\hbox {$^\circ $ }$ for continuity under the equivalence of antiparallel vectors as eigenvectors). The bottom panel shows the ellipticity angle of the mean polarization vector (thick line) along with the ellipticity angle of the first eigenvector, plotted twice with opposite signs.
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In the text

$\begin{figure} \par\begin{tabular}{@{\extracolsep{-5mm}}cccc} \hspace{6mm} PSR B... ...}} & \resizebox{!}{8cm}{\includegraphics{1029f4d.eps}}\end{tabular} \end{figure}$ Figure 4: Amplitude ( top) and phase ( bottom) of subpulse modulations, in total intensity (thick solid line) and polarization (semi-major axis ( $\vert\vec{A}\vert$ ): thick dashed, semi-minor axis ( $\vert\vec{B}\vert$ ): thick dotted). The phase of the semi-minor axis is not plotted, since by definition it is offset from that of the semi-major axis by $\pm$ $90\hbox {$^\circ $ }$ . In the left-most column only, the amplitude and phase of two OPMs (thin dotted and dashed lines) as inferred from the total intensity and semi-major axis values are plotted along with the phase difference (thin solid line). A constant slope was subtracted from all phases for clarity. The (dimensionless) slopes used were 25 for PSR B0809+74, -60 for PSR B0320+39, and 60 for PSR B0818-13.
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In the text

$\begin{figure} \par\includegraphics[width=7.5cm,clip]{1029f5.eps} \end{figure}$ Figure 5: Distribution of polarization orientations in pulse longitudes 39-40 $^\circ$ for PSR B0818-13 at 328 MHz. The projection is Lambert's azimuthal equal area, interrupted at the equator and centred on the poles of the Poincaré sphere ( $V/\vert\vec{p}\vert = \pm1$ ): see Edwards & Stappers (2004) for details. Meridians and parallels are marked at intervals of 30 $^\circ$ , with the upward vertical lines corresponding to a position angle of 0 $^\circ$ .
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In the text

$\begin{figure} \par\includegraphics[width=5.2cm,clip]{1029f6.eps} \end{figure}$ Figure 6: Illustration of the results of three-way polarization mode segregation (Deshpande & Rankin 2001) on the superposition of sinusoidal OPMs. a) Simulated intensity of two OPMs (in a given longitude bin) as a function of time. b) Resultant signal in the component of $\vec{p}$ corresponding to the modal orientations. c) Primary polarization mode intensity signal as inferred by three-way segregation (solid) and its fundamental Fourier component (dashed). d) As for (c) but for secondary mode. Note that the underlying OPMs are nearly in phase, while the fundamentals of the inferred signals are in pure anti-phase.
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In the text