Synoptic map of CR 2255 and the corresponding Potential Field Source Surface (PFSS), suggesting that the upflow region on 17 March 2022 is located in a region of open magnetic field lines. Top panel: GONG synoptic map of CR 2255. White (black) corresponds to positive (negative) polarity field; the field values have been saturated above (below) 60 G. Bottom panel: PFSS model of CR 2255. The tallest closed field lines are shown. All field lines that reach 2.5 R_⊙ are open by assumption, and so the tallest closed field lines are those with a vanishing radial component just below. Such field lines separate regions of open and closed magnetic fields. Coronal holes have their footprints at the photosphere represented by patches of colour: green denotes coronal holes with positive photospheric polarity and red with negative. In the plot, the neutral line on the source surface, which shows a quasi-sinusoidal pattern, is shown by a thick black line (see https://gong.nso.edu/data/magmap/fmodel.html). The black circle denotes the region of interest in both panels.