Statistical evolution of the electron temperature T_e (in eV) with respect to the distance of the Sun. The black dots, the red stars, and the yellow tripod solid line stand for T_e and the median of T_e determined with and without the secondary electrons removed, respectively. The purple dots and triangles correspond to T_e, sec and its median, determined from integrating the residuals at low energies (see text for more details). The color gradients with crosses, squares, pentagons, and diamonds represent the median T_e for four different SW populations (A, B, C, and D), extracted from the PSP and HELIOS missions by Dakeyo et al. (2022).