(a) Electron density as a function of time using the quasi-thermal noise spectroscopy technique with an automatic (black) and the manual (magenta) detection of the plasma peak. The blue curve represents the electron number densities inferred using the spacecraft potential data. (b) Zoom on n_e between 12:00 and 12:41 UT. The dashed lines mark boundary crossings and transitions between different regions from the solar wind, to the magnetosheath (MS) and the lobe of the tail region (highlighted in yellow).