Perpendicular (panel c) and parallel (panel d) proton temperatures measured from 15 to 100 solar radii (panel a) during Parker Solar Probe orbit 10. The solar wind speed (panel b) strongly correlates with the temperatures to the extent that the temperatures are asymmetric about perihelion. In panels e and f, a normalization factor has been applied to the temperatures to convert them from those measured at the local speed to those that would have been measured if the wind speed had been 400 km s⁻¹. This normalization makes the resulting temperatures maximum near perihelion and they decrease with radial distance in a manner consistent with adiabatic cooling.