Inferred maps of B_∥ from the four spectral windows summarized in Table 1. The panels are ordered according to their average formation height, as estimated using response functions. Panel a: photospheric estimate derived from the far wings of the Na I 5896 Å line. Panel b: upper photospheric estimate derived from the inner wing of the Na I 5896 Å line. Panel c: lower chromospheric estimate derived from the core of the Mg I 5173 Å line. Panel d: chromospheric estimate derived from the core of the Ca II 8542 Å line. The yellow contours indicate the area used to compute the spatial averages that are listed in the rightmost column in Table 1.