An evaluation of International Reference Ionosphere electron density in the polar cap and cusp using EISCAT Svalbard radar measurements

Bjoland, Lindis Merete; Belyey, V.; Løvhaug, U. P.; Hoz, C. La

doi:10.5194/angeo-34-751-2016

Cited by 33 publications

(26 citation statements)

References 23 publications

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“…In Themens and Jayachandran [2016], it was demonstrated that the IRI performs poorly in representing total electron content (TEC) in the polar cap, auroral oval, and subauroral regions, particularly during the equinoxes at high solar activity. These issues at high solar activity were also confirmed via incoherent scatter radar (ISR) observations by Bjoland et al [2016]. Themens et al [2014] showed that the IRI produces significant errors in its representation of the F 2 peak of THEMENS ET AL.…”

Section: Introductionmentioning

confidence: 75%

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

et al. 2017

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We present here the Empirical Canadian High Arctic Ionospheric Model (E‐CHAIM) quiet NmF2, perturbation NmF2, and quiet hmF2 models. These models provide peak ionospheric characteristics for a domain above 50°N geomagnetic latitude. Model fitting is undertaken using all available ionosonde and radio occultation electron density data, constituting a data set of over 28 million observations. A comprehensive validation of the model is undertaken, and performance is compared to that of the International Reference Ionosphere (IRI). In the case of the quiet NmF2 model, the E‐CHAIM model provides a systematic improvement over the IRI Union Radio Scientifique Internationale maps. At all stations within the polar cap, we see drastic RMS error improvements over the IRI by up to 1.3 MHz in critical frequency (up to 60% in NmF2). These improvements occur primarily during equinox periods and at low solar activities, decreasing somewhat as one tends to lower latitudes. Qualitatively, the E‐CHAIM is capable of representing auroral enhancements in NmF2, as well as the location and extent of the main ionospheric trough, not reproduced by the IRI. The included NmF2 storm model demonstrates improvements over the IRI by up to 35% and over the quiet time E‐CHAIM model by up to 30%. In terms of hmF2, over the validation periods used in this study, we found overall RMS errors of ~13 km for E‐CHAIM, with IRI2007 overall hmF2 errors ranging between 16 km and 22 km. The E‐CHAIM performs comparably to or slightly better than the IRI within the polar cap; however, significant improvements are found within the auroral oval.

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Section: Introductionmentioning

confidence: 75%

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

et al. 2017

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“…Themens and Jayachandran () show that the errors in the IRI‐generated topside thickness account for the majority of the errors in the IRI's representation of high‐latitude TEC. These errors were further verified by incoherent scatter radar (ISR) observations at several polar cap and auroral oval locations (Bjoland et al, ; Themens, Jayachandran, & Varney, ), where Themens, Jayachandran, and Varney () relate these errors to several different limitations in the current NeQuick parameterization. In the subauroral trough region, Xiong et al () showed that the IRI overestimates near peak and lower topside electron density by an average of 20%.…”

Section: Introductionmentioning

confidence: 81%

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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“…(2009). The satellite Ionospheric Pierce Points (IPPs) were estimated at an altitude of 350 km as it is believed that most of the high‐latitude scintillations are caused by irregularities at the F region peak altitude (Basu et al., 1978; Bjo˙land et al., 2016), although the production of scintillation at a lower altitude cannot be ruled out (Deshpande et al., 2016). The amplitude scintillation index ( S 4 ) is computed according to the following expression:

S_{4} = \sqrt{\frac{⟨ S I^{2} ⟩ - {⟨ S I ⟩}^{2}}{{⟨ S I ⟩}^{2}}},

where SI is the signal intensity.…”

Section: Chain and Data Reductionmentioning

confidence: 99%

Solar Cycle Variations of GPS Amplitude Scintillation for the Polar Region

et al. 2020

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Global Positioning System (GPS) L1 amplitude data, obtained using the Canadian High Arctic Ionospheric Network (CHAIN) during the period 2008–2018, is used to study the seasonal and solar cycle dependence of high‐latitude amplitude scintillation. The occurrence of amplitude scintillation is predominantly confined to the 10–18 magnetic local time (MLT) and 72–87° Altitude‐Adjusted Corrected Geomagnetic (AACGM) sector and is a winter and equinoctial phenomenon. The occurrence of amplitude scintillation shows a clear seasonal and solar cycle dependence with a maximum value of ∼11% during the high solar activity early winter periods, and a secondary maximum in equinoctial months, and almost no occurrence during summer months. This pattern in occurrence suggests that amplitude scintillation is a phenomenon that is closely associated with the presence of patches and particle precipitation events.

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An evaluation of International Reference Ionosphere electron density in the polar cap and cusp using EISCAT Svalbard radar measurements

Cited by 33 publications

References 23 publications

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

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

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

Solar Cycle Variations of GPS Amplitude Scintillation for the Polar Region

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An evaluation of International Reference Ionosphere electron density in the polar cap and cusp using EISCAT Svalbard radar measurements

Cited by 33 publications

References 23 publications

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

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

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

Solar Cycle Variations of GPS Amplitude Scintillation for the Polar Region

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

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