Time evolution of the electron density n_e (in cm⁻³), from July 8 to 15, 2021. The brown triangles represent n_e measured by RPW and time-shifted at the location of BepiColombo. The red stars and the blue dots are the density calculated with MEA 1, without and with the secondary electrons removed, respectively. The green diamonds correspond to the density of secondary electrons deduced by integrating the residuals at low energies (see details in the text).