A Bottomside Parameterization for the Empirical Canadian High Arctic Ionospheric Model

Abstract

In this study, we present a bottomside model representation to be used by the Empirical Canadian High Arctic Ionospheric Model (E-CHAIM). This model features a new approach to modeling the bottomside electron density; namely, instead of modelling electron density directly, E-CHAIM models the altitude profile of the scale thickness of a single bottomside layer. In this approach, the curvature in the bottomside associated with the E region and F1 layer is represented in the scale thickness domain as a peak function centered at the layer peak altitude. The use of this approach ensures the production of explicitly doubly differentiable bottomside electron density profiles and directly avoids issues known to exist within current standards, such as the International Reference Ionosphere (IRI), which has discontinuities in space, time, and in the vertical electron density gradient. In terms of performance, after removing the impacts of hmF2 and NmF2, the new E-CHAIM profile function generally performs comparably to the IRI, with bottomside TEC from both models within 2.0 TECU (1 TECU = 10 16 e/m 3 ) of observations. More specifically, the E-CHAIM bottomside is demonstrated to outperform the IRI bottomside function in the F region during low solar activity periods with respect to incoherent scatter radar observations. At high latitudes, E-CHAIM tends to outperform the IRI during winter months by between 10% and 40% of NmF2 while being outperformed by the IRI by between 10% and 25% of NmF2 during summer periods, mainly during the daytime at high solar activity.

E‐CHAIM as a Model of Total Electron Content: Performance and Diagnostics

“…and Themens, Jayachandran, McCaffrey, Reid, and Varney(2019) later detailing E-CHAIM's topside and bottomside,Writing - original draft: D. R. Themens Writing - review & editing: D. R. Themens, Ben Reid, P. T. Jayachandran, Bion Larson, A. V. Koustov, Sean Elvidge, A. M. McCaffrey, Chris Watson 10.1029/2021SW002872…”

A Comparison of the Topside Electron Density Measured by the Swarm Satellites and Incoherent Scatter Radars Over Resolute Bay, Canada

“…The data spread is much more significant in our case. This is not a surprise because the polar cap ionosphere generally has lower densities (Themens et al, 2017(Themens et al, , 2019 and it is much more patchy (e.g., Chartier et al, 2018;Moen et al, 2007). For the linear fit line applied to all the points in Figure 6, a typical slope was found to be 0.62, which is a slower dependence than that of Lomidze et al (2018).…”

“…These models seem to perform reasonably well with respect to the peak electron density at middle latitudes, but they still require improvements at high latitudes (Bjoland et al, 2016;Themens et al, 2017). One example of an improved ionospheric model for high latitudes is the recently developed Empirical Canadian High Arctic Ionospheric Model (E-Chaim, Themens et al, 2017Themens et al, , 2019.…”

Comparison of SuperDARN peak electron density estimates based on elevation angle measurements to ionosonde and incoherent scatter radar measurements

“…Decades of research has led to a general understanding of the horizontal and vertical distributions of the electron density in the ionosphere, culminating in the development of empirical models of the ionosphere such as the International Reference Ionosphere (IRI, Bilitza et al 2017) and the Empirical Canadian High Arctic Ionospheric Model (E-CHAIM, Themens et al 2017Themens et al , 2019, which is an improved empirical model for high-latitude regions.…”

“…One important aspect of both ionosonde and ISR operations is that the region of measurements is reasonably constrained and known. This is necessary for multi-instrument studies, and for the development of ionospheric models, such as the IRI series (Bilitza 2018), E-CHAIM and others (e.g., Themens et al 2017Themens et al , 2019. However, for some applications a global coverage is highly desired.…”