Latitudinal Variation of the Background Solar Wind in the Inner Heliosphere from Multi-Spacecraft Observations

In order to improve the predictions of the ambient solar wind plasma at planets, moons, comets, and interplanetary spacecraft, we are conducting a multi-spacecraft investigation to study the spatial variation and temporal evolution of solar wind structures. Here we present our results on the spatial variation by investigating the impact of latitudinal spacecraft-target separation on extrapolation accuracy. Using ballistically propagated bulk velocity datasets of the ACE, STEREO A, Parker Solar Probe, and Solar Orbiter spacecraft, we perform statistical analyses and case studies. Our findings indicate that a separation of even a few degrees in latitude can introduce errors into propagation accuracy and needs to be taken into account when incorporating in-situ measurements into solar wind forecasting. We further investigate the role of the heliospheric current sheet in this phenomenon by utilizing coronal modeling. The results are useful in supporting out-of-ecliptic solar wind observations and for the improvement of propagation models.