Map of interstellar polarization at high northern galactic latitudes: rectangular projection. The map shows the latitude range from 30° to 70°. The length of the bar is proportional to the value of polarization P. Thin vertical dashed lines show the eastern (255° < l < 300°), central (300° < l < 360°), and western (0° < l < 45°) latitude zones of the magnetic loop. Thick dashed lines show the outer walls of Wolleben’s S1 and S2 shells and the thick solid line shows the contour of the interaction ring between the Local Bubble and Loop I (see Sects. 8.2 and 8.3 for explanation).