1 Introduction The topside ionosphere is the region connecting the F2-layer electron density peak to the plasmasphere. It is a highly dynamic region where, as altitude increases, ionospheric plasma composition shifts from O+-dominated to H+-dominated, while plasma temperatures rise and plasma densities decrease due to plasma ambipolar diffusion along geomagnetic field lines (Banks, 1969; Bauer, 1969; Pignalberi, Pezzopane, Nava et al., 2020; Schunk & Nagy, 1978).
