Bald patch between N₂ and . (a) Photospheric vector magnetogram of the BP region. The FOV of this panel is indicated by the green box in Fig. 2h1. The B_z component of the field is plotted as the background, saturating at ±600 G. The red (blue) arrows denote the horizontal component (B_h) of the field that correspond to the positive (negative) polarities. The green line indicates the PIL between and the group of N₁ and N₂, which is obtained at the contour line of B_z = 0. The yellow parts of the PIL mark the BP section. (b) Values of (B_h · ∇_hB_z)|_PIL (shown in green) and the shear angle S (shown in magenta) of all pixels along the PIL. The two vertical-dashed lines in (b) enclose the BP region.