A new expression for computing topside scale height for satellite-based communications

It is well-known that the NeQuick 2 model provides analytical expressions showing a relationship between topside and bottomside ionospheres. Its bottomside thickness parameter (B2bot) is a key parameter for studying topside electron density profile (EDP) and topside parameters, and its topside scale height (Hsc) is also used to identify the topside electron density profile. The B2bot computed using ionogram-derived ionospheric parameters can be used to calculate the Hsc. Unfortunately, the Hsc computed by the original B2bot expression (Hsc old) are significantly higher than the scale heights obtained from digisondes (Hm) and the diurnal variations of the Hsc old are quite different from those of the Hm. Hence, a new expression of B2bot for computing the Hsc is suggested in this work relying on the available expressions of the NeQuick 2 model. Our results show that (1) the Hsc computed by the new expression of B2bot (Hsc new) are comparable to the Hm and the diurnal variations in Hsc new are the same trends as those in Hm; (2) all of the scale heights show diurnal variations with higher values during daytime than during nighttime and the secondary peaks can be found different local times relying on the locations; and (3) the peaks of scale height cause higher absolute differences between Hsc new and Hm (D SH).