Radial evolution of Alfvénicity, Alfvén Mach number, and the α-to-proton temperature ratio in the solar wind. Panels (a), (b): correlation between proton velocity and magnetic-field fluctuations. Panels (c,d): correlation for α particles. The bold dashed line in (a)–(d) marks the Alfvénicity criterion ﹩{C}_{vB}^{{\prime} }=0.9﹩. Panels (e,f): v_p/v_A (bold dashed line at v_p/v_A = 1). Panels (g,h): T_α/T_p (bold dashed line at T_α/T_p = 4).