Scatter plots of 1-CR averages of V₀−V₇, the solar wind speed difference between the equator and 7° latitude, with solar activity. Top: the inter-quartile range of V₀−V₇ as a function of sunspot number (left) and sunspot cycle phase (right), where solar minimum is 0 and 1, and solar maximum is approximately 0.5. Bottom: the median of V₀−V₇ as a function of sunspot number (left) and sunspot cycle phase (right). In all panels, solar cycles 21, 22, 23, and 24 have been coloured black, red, blue, and white, respectively.