The Empirical Canadian High Arctic Ionospheric Model (E‐CHAIM): NmF2 and hmF2

Themens, David R.; Jayachandran, P. T.; Galkin, I. A.; Hall, Chris M.

doi:10.1002/2017ja024398

Cited by 86 publications

(63 citation statements)

References 40 publications

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“…We note that the daytime electron density profiles are maximized at lower heights compared to the nighttime profiles, as shown in Figures 6b and 6c. This is a known result from other observations as well, for example, Themens et al (2017). Since for all PolarDARN radars considered, the geometrical aspect angles are better at lower heights, smaller density is required to achieve orthogonality during daytime.…”

Section: 1029/2018rs006566supporting

confidence: 62%

Optimal F Region Electron Density for the PolarDARN Radar Echo Detection Near the Resolute Bay Zenith

et al. 2018

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Operation of over‐the‐horizon radars comprising the Super Dual Auroral Radar Network (SuperDARN) relies on strong ionospheric refraction of high‐frequency (HF, f = 10–15 MHz) radiowaves such that in order to provide reliable coverage of a given geographic location, the working frequency has to be optimized with respect to the ionospheric conditions. In this work, joint observations of the Rankin Inlet, Inuvik, and Clyde River PolarDARN/SuperDARN HF radars near the Resolute Bay (RB) zenith, where the incoherent scatter radars that monitored the electron density distribution in the ionosphere, are used to assess the F region peak electron density required for HF echo detection near the RB zenith. We show that the echo occurrence rate increases with the electron density up to Ne ≈ (2 − 3) ⋅ 1011 m−3, and above this value, the occurrence rate saturates. Thus, optimum electron density for echo detection exist for every HF radar. The saturation effect is more pronounced for the Clyde River radar whose ranges of echo detection are smallest. The saturation in the dependence is reached at smaller densities for the Inuvik radar whose location is farthest from RB and for lower transmitting frequency of observations for every radar. The data presented suggest that having strong‐enough electron density in the ionosphere is the major factor for detection of HF echoes in winter or equinox.

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Section: 1029/2018rs006566supporting

confidence: 62%

Optimal F Region Electron Density for the PolarDARN Radar Echo Detection Near the Resolute Bay Zenith

et al. 2018

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“…To examine the spatial and geomagnetic activity variations of the observed errors in model-derived H 0 , we have plotted the mean errors with respect to geomagnetic latitude, magnetic local time (MLT), and integrated auroral electrojet (AE) index in Figure 5. The integrated AE index that is used here is calculated in the same manner as described in Themens, Jayachandran, Galkin, et al (2017) and follows the methodology of Wu and Wilkinson (1995) and Perrone et al (2001). In terms of variations with respect to geomagnetic latitude, we see a tendency for the IRI to overestimate H 0 below 70°N by an average of~10 km and standard deviation of~10 km.…”

Section: H 0 Parameterizationmentioning

confidence: 96%

“…The E-CHAIM, first introduced in Themens, Jayachandran, Galkin, et al (2017), is an empirical representation of ionospheric electron density above 45°N geomagnetic latitude. The model is composed of separate models for the each of h m F 2 , N m F 2 , topside vertical shape, and bottomside vertical shape.…”

Section: A Topside For E-chaimmentioning

confidence: 99%

“…In section 4.2, we refit the NeQuick parameterization of H 0 , first in a manner that preserves the form of the original model and later in a new form. Finally, in section 4.3, we build on the results of sections 3 and 4.1 to present a proposed parameterization for the topside representation in the E-CHAIM (Themens, Jayachandran, Galkin, et al, 2017).…”

Section: Introductionmentioning

confidence: 99%

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Topside Electron Density Representations for Middle and High Latitudes: A Topside Parameterization for E‐CHAIM Based On the NeQuick

et al. 2018

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In this study, we present a topside model representation to be used by the Empirical Canadian High Arctic Ionospheric Model (E‐CHAIM). In the process of this, we also present a comprehensive evaluation of the NeQuick's, and by extension the International Reference Ionosphere's, topside electron density model for middle and high latitudes in the Northern Hemisphere. Using data gathered from all available incoherent scatter radars, topside sounders, and Global Navigation Satellite System Radio Occultation satellites, we show that the current NeQuick parameterization suboptimally represents the shape of the topside electron density profile at these latitudes and performs poorly in the representation of seasonal and solar cycle variations of the topside scale thickness. Despite this, the simple, one variable, NeQuick model is a powerful tool for modeling the topside ionosphere. By refitting the parameters that define the maximum topside scale thickness and the rate of increase of the scale height within the NeQuick topside model function, r and g, respectively, and refitting the model's parameterization of the scale height at the F region peak, H0, we find considerable improvement in the NeQuick's ability to represent the topside shape and behavior. Building on these results, we present a new topside model extension of the E‐CHAIM based on the revised NeQuick function. Overall, root‐mean‐square errors in topside electron density are improved over the traditional International Reference Ionosphere/NeQuick topside by 31% for a new NeQuick parameterization and by 36% for a newly proposed topside for E‐CHAIM.

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“…The above models all provide quiet time, climatological representations of electron density, while both the IRI (Bilitza & Reinisch, 2008) and E-CHAIM (Themens, Jayachandran, Galkin, & Hall, 2017) provide supplemental adjustments to their quiet time models to account for storm-time variability. These adjustment models are hereafter referred to as Storm models.…”

Section: Introductionmentioning

confidence: 99%

The Limits of Empirical Electron Density Modeling: Examining the Capacity of E‐CHAIM and the IRI for Modeling Intermediate (1‐ to 30‐Day) Timescales at High Latitudes

et al. 2020

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The Empirical Canadian High Arctic Ionospheric Model (E-CHAIM) is a new empirical 3-D electron density model intended as an alternative to the use of conventional standards, such as the International Reference Ionosphere (IRI), at high latitudes (above 50°N). In this study, we have manually scaled a year of data from two Canadian High Arctic Ionospheric Network (CHAIN) ionosondes. Using this high-quality data, we examine the behavior of the polar cap ionosphere under disturbed geomagnetic conditions and assess the capacity of E-CHAIM to model polar cap F2-peak electron density variability on "weather-like," intermediate timescales (1-30 days). This is a particularly challenging environment for monthly median empirical models due to the regular occurrence of variations about the monthly mean of up to 2 MHz. We demonstrate in this study that E-CHAIM's storm model is capable of explaining 4 to 25% of polar cap foF2 variance at 1-to 30-day timescales and 5 to 50% of the amplitude of that variability, while the IRI's Storm-Time Ionospheric Correction Model (STORM) only explains 0.2 to 9% of the variance at these timescales and no more than 5% of their amplitude. While the IRI's STORM model provided no measurable improvement over the monthly median, E-CHAIM's storm parameterization was able to improve overall root-mean-square errors by 0.05 to 0.1 MHz over its quiet time model. The overall improvement through the use of storm foF2 parameterizations is found to be limited, but measurable, particularly during storm periods, where an average improvement in root-mean-square error of 20% is observed. Key Points:• E-CHAIM outperforms the IRI at 1to 30-day timescales within the polar cap • E-CHAIM is capable of explaining 4-25% of the foF2 variance at storm timescales at high latitudes • Storm models are capable of improving overall model performance beyond the best monthly median representation

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The Empirical Canadian High Arctic Ionospheric Model (E‐CHAIM): N_mF₂ and h_mF₂

Cited by 86 publications

References 40 publications

Optimal F Region Electron Density for the PolarDARN Radar Echo Detection Near the Resolute Bay Zenith

Optimal F Region Electron Density for the PolarDARN Radar Echo Detection Near the Resolute Bay Zenith

Topside Electron Density Representations for Middle and High Latitudes: A Topside Parameterization for E‐CHAIM Based On the NeQuick

The Limits of Empirical Electron Density Modeling: Examining the Capacity of E‐CHAIM and the IRI for Modeling Intermediate (1‐ to 30‐Day) Timescales at High Latitudes

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