Distributions (presented in colour with coding indicated by the right-hand bars) of the number of our data a) and the compressibility, b) plotted in the parameter plane of the normalized wave power versus the proton temperature anisotropy, T_⊥p/T_∥p; c) weighted mean value of the proton temperature anisotropy for A_c < 0.1 (black), and A_c > 0.2 (green) displayed versus normalized wave power. The short vertical bars indicate the small uncertainties of the weighted mean values.