Top panel: Carrington map from SDO-AIA EUV observations on 2019 March 31 at 00:00 UT and at 193 Å. Bottom panel: Carrington map from SOHO-LASCO C3 white-light observations on 2019 April 3 at 12:00 UT and at a height of 5 R_⊙. Both Carrington maps, although they are synoptic maps over the full solar rotation, are continuously updated as new images become available. The time label associated to the Carrington maps therefore corresponds to the date (and time) of the last update. The PSP trajectory (dark solid line) is projected at the height of the Carrington maps (and at 2.1 R_⊙ for the AIA EUV map), using the Parker spiral (Parker 1958) and the solar wind speed measured in situ at PSP. Along the PSP projected trajectory, some PSP projected positions for several dates and times are depicted with colored stars and arrows. In the zoom-in views on the middle panels, the plasma electron density n_e(35.6 R_⊙) (in cm⁻³) (FIELDS/RFS(QTN)) is plotted along the PSP projected trajectory with a logarithmic color scale. The red- and dark-dashed lines represent the neutral line from the PFSS model (described in Section 4). Open field regions of positive (negative) polarity from the PFSS model are represented at the photosphere by a semitransparent blue (red) layer.