Distributions (presented in colour with coding indicated by the right-hand bars) of the number of our data a), the collision age, A_c b) and the ratio between the temperature anisotropies of alpha particles and protons, (T_⊥αT_∥p)/(T_∥αT_⊥p), c). All parameter are plotted in the plane of the normalized wave-power, , versus normalized ion differential speed, V_αp/V_A; d) weighted mean values of the collisional age, A_c, and the ratio between the temperature anisotropies of alpha particles and protons, (T_⊥αT_∥p)/(T_∥αT_⊥p), displayed versus normalized ion differential speed, V_αp/V_A. The white dots in panel a) represent the weighted mean values. The vertical dotted line in panel d) separates the regimes of fast and slow solar wind.