20° × 20° patch of the high-pass filtered Commander CMB polarization map, centred on the north ecliptic pole, (l,b) = (96°,30°). Each map is pixelized with a HEALPix resolution of N_side = 1024, and has an angular resolution of 10′ FWHM. The top row shows Q and U maps derived from the full-mission data set, the middle row shows the corresponding E and B maps, and the bottom row shows the E- and B-modes of the half-ring half-difference (HRHD) map. Note the characteristic “+” and “×” patterns in the Q and U maps, and the clear asymmetry between E and B in the full data set. Also note that the HRHD (null) E map is consistent with both the full and HRHD B maps.