Comparison of footpoint locations for PFSS extrapolations (R_ss = 2.5 R_⊙ and ℓ_max = 88) using SSW (blue squares), ADAPT HMI (pink dots) and ADAPT GONG (yellow triangles) synchronic magnetic maps from December 16, 2011, as the photospheric boundary condition. Although the SSW maps allow for a slightly higher resolution (ℓ_max = 94), we adopt ℓ_max = 88, i.e., the maximum value permitted by the angular resolution of the ADAPT maps, to ensure a consistent comparison among the three maps. The STEREO-A/EUVI 304 Å image of the brightening on December 16 at 04:36 UT is also shown, with the brightening location marked by the white arrow.