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tokens: 3 (d), and can be compared with the MHD results in panel (a). There are several similarities between the two solutions, although also some important distinctions. First, both solutions produce two equatorial coronal holes at roughly the same Carrington longitudes. Additionally, both solutions map to the same positive-polarity equatorial coronal hole for roughly the same intervals, spanning the first encounter. However, the size and shape of the equatorial holes are substantially different, with the PFSS solution producing much smaller areas, in spite of the fact that we set the source surface radius to 2.0 R S , which is typically lower than is usually used, and chosen to open coronal holes as much as possible. Moreover, prior to first encounter, the PFSS solution mapped to the negative-polarity southern polar coronal hole, and, thus, this transition would not be associated with a current sheet crossing. By flying PSP ’s trajectory through the heliospheric solution, we are able to recover the predicted plasma and magnetic field variables in situ. These are summarized in Figure 4 . The panels show, from top to bottom, radial speed, radial component of the magnetic field ( B r ), scaled B r , plasma number density ( N p ), scaled N p , and the heliocentric position of the spacecraft, as summarized by distance ( R ) and Carrington longitude. Focusing first on panels (a), (b), and (d), we note the following points. First, the speed remained approximately constant during the interval from first encounter to second encounter (∼525 km s −1 ). Second, the magnetic field switched from positive polarity to negative polarity (day of year: 302), and remained so for approximately three weeks. It also increased to a maximum negative value of −80 nT. Third, plasma density rose to almost 80 cm −3 ; however, the peak in density lagged the magnetic field peak by approximately one day. Figure 4. Time series of predicted (a) radial velocity ( v r ), (b) radial magnetic field ( B r ), (c) scaled B r , (d) plasma number density ( N p ), (e) scaled N p , and (f) location of spacecraft in terms of heliocentric distance (aqua) and Carrington longitude (magenta). In (c) and (e), the radial magnetic field and number density have been scaled by r 2 to account for the radial fall-off expected from flow into a spherical geometry. These variations, however, are misleading, in the sense that both the density and radial magnetic field fluctuations lie on top of the geometric expansion of the solar wind, which naturally produces a 1/ r 2 fall off with heliocentric distance, or, because the spacecraft is moving toward perihelion, an increase of r 2 . To address this, in panels (c) and (e) of Figure 4 , we have removed the 1/ r 2 variation and scaled the measurements to 1 au values. Both the values and variations are markedly different (compare panels (b) and (c) and panels (d) and (e)). Now, B r remains virtually flat (∼8 nT) for the entire duration of the encounter. Number