On the Analytical Description of the Topside Ionosphere by NeQuick: Modeling the Scale Height Through COSMIC/FORMOSAT-3 Selected Data

Abstract

The analytical description of the topside ionosphere included in the NeQuick model is studied in detail. First, the modeled scale height behavior is analyzed at infinity and for the lowest part of the topside region; in the latter case, the analysis is done through an expansion in Taylor series near the F2-layer peak. Moreover, the significant influence of the three NeQuick topside parameters in the modeling of the topside profile is investigated in detail and, in particular, it is shown that for the lowest part of the topside the model assumes a linearly increasing trend of the topside scale height. Second, the topside formulation is inverted to derive a fully analytical expression of the topside scale height as a function of the electron density and F2-layer peak parameters. This expression has been applied to a selected and very reliable dataset of Constellation Observing System for Meteorology, Ionosphere, and Climate (COSMIC)/FORMOSAT-3 radio occultation profiles. Statistical analyses strongly support the hypothesis embedded in NeQuick regarding the linear trend of the topside scale height for the lowest part of the topside. Index Terms-Constellation Observing System for Meteorology, Ionosphere, and Climate (COSMIC)/FORMOSAT-3 radio occultation data, NeQuick model, topside ionosphere modeling, topside scale height. I. INTRODUCTION T HE topside part of the ionosphere extends from the height of the F2-layer peak, corresponding to the ionospheric electron density maximum (NmF2), to the plasmasphere [1]. Developing a reliable model of the topside ionosphere is one of the most difficult tasks because instruments commonly used

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

“…The rate of the electron density decrease in the topside is driven by the topside effective scale height H Epstein (z) as described in Pignalberi et al 13 : By applying Eq. (9), it was possible to calculate the topside effective scale height H Epstein (z) for each height z by using COSMIC retrieved N e (z), NmF2, and hmF2 values 13 . Some examples of this procedure are shown in Figs 13 .…”

“…(9), it was possible to calculate the topside effective scale height H Epstein (z) for each height z by using COSMIC retrieved N e (z), NmF2, and hmF2 values 13 . Some examples of this procedure are shown in Figs 13 .…”

“…In order to verify this desired behavior, we further developed the calculation, with the change of variable z = n • 2H Epstein (z) , n ∈ R + 0 , and evaluated VSH and corresponding derivatives through Eqs. (13) and 15:…”

“…This allowed to work on a very reliable dataset of topside electron density profiles 35 . The Pignalberi et al 13 technique is here applied to the entire COSMIC RO dataset, recorded from 2006 to 2018, to retrieve preliminary information on the effective vertical scale height dependence on diurnal, seasonal, solar activity, and spatial variabilities. COSMIC/FORMOSAT-3 was a six microsatellites constellation launched on 15 April 2006 and deployed into a circular orbit (with 72° of inclination) at about 800 km of altitude (reached at the end of 2007) and a separation angle of 30° in longitude between neighboring satellites 36 .…”

“…In Pignalberi et al 13 , H Epstein (z) values retrieved by COSMIC RO topside electron density values through Eq. (9) were linearly fitted to calculate corresponding slope and intercept values.…”