Empirically derived heating rates for protons (solid lines) and electrons (dashed lines) in the fast solar wind, with multiple curves showing results for u = 600, 650, 700, 750, and 800 km s ⁻¹ (from bottom to top for each set of curves). Shown for comparison is Q _turb (Equation (15)) for five values of λ _⊥ at 1 AU (dotted lines). All heating rates have been multiplied by ( r/1 AU) ⁴. Example error bars are given for the u = 700 km s ⁻¹ case (see the text).