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For the past 30+ years, the magnetic expansion factor ($f_s$) has been usedin empirical relationships to predict solar wind speed ($v_{obs}$) at 1 AU,based on an inverse relationship between these two quantities. Coronal unipolarstreamers (i.e. pseudostreamers) undergo limited field line expansion,resulting in $f_s$-dependent relationships to predict fast wind associated withthese structures. However, case studies have shown that in situ observedpseudostreamer solar wind was much slower than that derived with $f_s$. Toinvestigate this further, we conduct a statistical analysis to determine if$f_s$ and $v_{obs}$ are inversely correlated for a large sample of periods whenpseudostreamer wind was observed at multiple 1 AU spacecraft (i.e. ACE,STEREO-A/B). We use the Wang-Sheeley-Arge (WSA) model driven by Air Force DataAssimilative Photospheric Flux Transport (ADAPT) photospheric field maps toidentify 38 periods when spacecraft observe pseudostreamer wind. We compare theexpansion factor of the last open field lines on either side of apseudostreamer cusp with the corresponding in situ measured solar wind speed.We find only slow wind ($v_{obs}$ $<$ 500 km/s) is associated withpseudostreamers, and that there is not a significant correlation between $f_s$and $v_{obs}$ for these field lines. This suggests that field lines near theopen-closed boundary of pseudostreamers are not subject to the steady-stateacceleration along continuously open flux tubes assumed in the $f_s$-$v_{obs}$relationship. In general, dynamics at the boundary between open and closedfield lines such as interchange reconnection will invalidate the steady-stateassumptions of this relationship.

On the Relationship between Magnetic Expansion Factor and Observed Speed of the Solar Wind from Coronal Pseudostreamers