Ratio of slow to fast solar wind for a SSN lagged by 3 yr. The yearly ratios (+) and their weighted linear fit (solid line) are obtained from OMNI data with a threshold velocity of v_th = 400 km s⁻¹. The error bars denote the SSN standard deviation and the relative weight from the yearly data coverage. The model’s balance parameter (9) and derived ratio (same threshold) are plotted as dashed and dotted lines.