Simulation results reproduce the large-scale features of the NH solar wind speed measurements driven by the solar wind source and the gradual slowing of the solar wind as interstellar material is picked up. In the top panel, we show solar rotation–averaged (25.38 days) solar speed measurements at NH (orange) as a function of distance from the Sun along with simulated speeds from two runs: one that includes interstellar pickup ions (green) and one that does not (purple). In both simulations the inner boundary is driven with 1 au observations. In the bottom panel, we show the percent difference between the simulation speeds for runs with and without pickup ions included as a function of distance. The rate of slowing with distance is represented well with a single linear fit with a slope of ∼0.27 % au⁻¹.