Semiempirical Model for Ionospheric Absorption based on the NRLMSISE‐00 atmospheric model

Abstract

The strength of high‐frequency radio signals, when refracted by the ionosphere, can be strongly influenced by ionospheric absorption. Accurate modeling of the amount of this absorption is a vital part of many studies of radio waves propagating in the ionosphere. We have developed a new, flexible model of ionospheric absorption, the Semiempirical Model for Ionospheric Absorption based on the NRLMSISE‐00 atmospheric model (SiMIAN). This article describes the methods and formulae used by SiMIAN, a comparison of SiMIAN with an older absorption model, and validation work performed by simulating the power returned in vertical incidence soundings of the ionosphere and comparing the results with real soundings.

Global modeling of the low‐ and middle‐latitude ionospheric D and lower E regions and implications for HF radio wave absorption

“…Our results show that the contributions to total HF absorption are often different for low latitude versus midlatitude to high latitude. For the conditions evaluated by Pederick and Cervera [] (latitude < 30°), we also find that the absorption maximizes in the lowermost E region near 95 km. Absorption at latitudes poleward of 40° contain, for much of the year and particularly in winter, a significant contribution from the D region at 80–90 km due to the role of nitric oxide.…”

“…MoJo assumes ν m = ν eff where ν eff is the sum of the temperature and composition‐dependent electron‐neutral ν e n and electron‐ion ν e i collision frequencies, representative of the average over the electron energy distribution function from Schunk and Nagy [, ]. Later we will qualitatively compare our results with Pederick and Cervera [, hereinafter PC14], which utilizes the Sen and Wyller [] dispersion relation to calculate the refractive index of the radio wave and thus the absorption.…”

“…Another reason for recent interest in the D region is that, as discussed by Eccles et al [], there has been a renewal of interest in the use of HF radio for both defense and commercial applications [see also McNamara et al , ; Ads et al , ]. Further, introducing a new model of HF absorption, Pederick and Cervera [] show that they get more absorption in the 90–100 km layer than the older calculations and that this “contradicts” the classic picture, dating back to work by Appleton and Piggott []. It is therefore of interest to extend our model/data comparison to explore its implications for HF absorption.…”

Implications of odd oxygen observations by the TIMED/SABER instrument for lower D region ionospheric modeling

“…This appears to have been unrecognized previously in the literature; however, our theoretical results appear consistent with other models and the observational data are consistent with independent datasets. This discrepancy is important since the HF absorption profiles recently presented by Pederick and Cervera (2014) show a secondary enhancement between 60 and 70 km, right where our model-data discrepancy is largest. Thus to understand HF propagation in the lower ionosphere, we need to resolve this discrepancy.…”

A directional HF noise model: Calibration and validation in the Australian region

“…The losses due to absorption by the ionosphere are calculated using the SiMIAN absorption model [Pederick and Cervera, 2014]. This model integrates the absorption coefficient (the imaginary component of the complex refractive index) along a ray path, with the absorption coefficient calculated using the Sen-Wyller formula [Sen and Wyller, 1960] and the NRLMSISE-00 atmospheric model [Picone et al, 2002].…”