Top panels: line-of-sight photospheric magnetic field for the three coronal-hole regions: CH1 (left), CH2 (middle), CH3 (right). The field values are saturated at ±50 Gauss to accentuate the contrast. Red lines denote the coronal-hole boundary and yellow boxes denote the three types of regions used to calculate the statistics presented in Table 3. Bottom panels: H maps and potential magnetic-field extrapolations of the photospheric fields in the top panels. Regions A in the CHs are characterized mostly by open fields; regions B in the QS are dominated by closed fields; regions C in the QS present a mixture of closed loops (short and long, which appear open locally) and open-field lines.