Profile evolution of pulsar B at 820 MHz, during BP1, BP2, and the IP, corresponding to two MJD bins: (top half) MJD53400–53500 and (bottom half) MJD53700−53800. Each profile comes from averaging the original data in the corresponding MJD bin and an orbital-phase interval of Δϕ_asc/2π = 0.02, centred around the orbital phase, ϕ_asc, shown in each panel. The number of single pulses averaged to obtain each profile are also shown at the top-left corner of each panel. The grey, vertical dashed lines at pulse phase 0.5 are used here to guide the eye and to highlight the relative changes between profiles observed during most BPs. We note that the profile alignment in this figure can only be used to compare the profiles of a single MJD bin and orbital-phase window (see main text for details). The blue, vertical error bar next to each profile corresponds to the quadrature sum of the off-pulse RMS of the profile shown, σ_stat, and the average RMS due to systematic pulse-to-pulse variations of the profiles that were summed to obtain the profile shown (see Sect. 3.2.2). For comparison, we have overlaid the analytic WP template profile of Fig. 4 with the observed average profiles corresponding roughly to the middle of BP1, BP2, and the IP.