On the link between the topside ionospheric effective scale height and the plasma ambipolar diffusion, theory and preliminary results

Abstract

Over the years, an amount of models relying on effective parameters were implemented in the challenging issue of the topside ionosphere description. These models are based on different analytical functions, but all of them depend on a parameter called effective scale height, that is deduced from topside electron density measurements. As their names state, they are effective in reproducing the topside electron density profile only when applied to the analytical function used to derive them. Then, in principle, they do not have any physical meaning. It is the goal of this paper to mathematically link the effective scale height modeled through the Epstein layer to the vertical scale height theoretically deduced from the plasma ambipolar diffusion theory. Firstly, effective and theoretical scale heights are linked through a mathematical relation by showing that they tend to each other in the topside ionosphere. Secondly, their connection is preliminarily demonstrated by calculating effective scale height values from the entire COSMIC/FORMOSAT-3 radio occultation dataset. Thirdly, a possible connection between the vertical gradient of the topside scale height (as obtained by COSMIC/FORMOSAT-3 satellites) and the electron temperature (as obtained by ESA Swarm B satellite) is studied by highlighting corresponding similarities in the diurnal, seasonal, solar activity, and latitudinal variability.

Validation and Improvement of NeQuick Topside Ionospheric Formulation Using COSMIC/FORMOSAT‐3 Data

“…This is evident from Figure 19 which is in agreement with recent evidence by Pignalberi, Pezzopane, Nava, et al. (2020) and Pignalberi, Pezzopane, Themens, et al. (2020) that the gradient of the modeled topside scale height (which is equivalent to g according to Equation ) exhibits a distinct global spatial variation pattern with a clear increasing trend as a function of latitude.…”

“…in accordance to Pignalberi, Pezzopane, Nava, et al. (2020) and Pignalberi, Pezzopane, Themens, et al. (2020), as shown below: Let, so that the equation becomes: By using the Sridhar Acharya formula, the solution for the above quadratic equation reduces to: …”

“…Pignalberi, Pezzopane, Nava, et al. (2020) and Pignalberi, Pezzopane, Themens, et al. (2020) demonstrated that the effect of r on the scale height becomes significant for altitudes much higher than the F2 peak.…”

“…Pignalberi, Pezzopane, Nava, et al. (2020) and Pignalberi, Pezzopane, Themens, et al. (2020) have recently underlined the significance of parameters r and g in the topside scale height variation near the F2‐layer peak (up to about 800 km).…”

Topside Ionosphere and Plasmasphere Modelling Using GNSS Radio Occultation and POD Data

“…However, future investigations are still necessary mainly to check model capabilities to represent the topside features during storm conditions. Additionally, further data fusion with bottomside measurements is still necessary for a complete specification of the ionosphere and recent improvements in NeQuick [31,32] should also be considered in future analysis.…”