Comparison of Total Electron Content with International Reference Ionosphere Model Predictions near the Northern Crest of EIA at Bangladesh

Global navigation satellite system (GNSS) can provide dual-frequency observation data, which can be used to effectively calculate total electron content (TEC). Numerical studies have utilized GNSS-derived TEC to evaluate the accuracy of ionospheric empirical models, such as the International Reference Ionosphere model (IRI) and the NeQuick model. However, most studies have evaluated vertical TEC rather than slant TEC (STEC), which resulted in the introduction of projection error. Furthermore, since there are few GNSS observation stations available in the Antarctic region and most are concentrated in the Antarctic continent edge, it is difficult to evaluate modeling accuracy within the entire Antarctic range. Considering these problems, in this study, GNSS STEC was calculated using dual-frequency observation data from stations that almost covered the Antarctic continent. By comparison with GNSS STEC, the accuracy of IRI-2016 and NeQuick2 at different latitudes and different solar radiation was evaluated during 2016–2017. The numerical results showed the following. (1) Both IRI-2016 and NeQuick2 underestimated the STEC. Since IRI-2016 utilizes new models to represent the F2-peak height (hmF2) directly, the IRI-2016 STEC is closer to GNSS STEC than NeQuick2. This conclusion was also confirmed by the Constellation Observing System for Meteorology Ionosphere and Climate (COSMIC) occultation data. (2) The differences in STEC of the two models are both normally distributed, and the NeQuick2 STEC is systematically biased as solar radiation increases. (3) The root mean square error (RMSE) of the IRI-2016 STEC is smaller than that of the NeQuick2 model, and the RMSE of the two modeling STEC increases with solar radiation intensity. Since IRI-2016 relies on new hmF2 models, it is more stable than NeQuick2.

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Influence of the Ionosphere Model on the Solution of a VLBI Geodetic Experiment

Symposium - International Astronomical Union ◽

10.1017/s0074180900135582 ◽

1988 ◽

Vol 129 ◽

pp. 551-552

Author(s):

G. Petit ◽

J. F. Lestrade ◽

C. Boucher ◽

F. Biraud ◽

A. Rius ◽

...

Keyword(s):

South America ◽

Total Electron Content ◽

Dual Band ◽

Single Frequency ◽

Electron Content ◽

Critical Aspect ◽

Total Electron ◽

Geodetic Vlbi ◽

Ionosphere Model ◽

First Time

The GRIG-2 geodetic VLBI experiment was conducted in 1985, linking for the first time South America, Europe and Africa. At the single frequency band of 1.66 GHz which was used, the monitoring of the ionosphere is a critical aspect and several predictions of Total Electron Content (TEC) were used. One of them is derived from dual band Doppler observations of TRANSIT satellites, which were simultaneously conducted. The influence of these models on the solution is presented, with comparisons with other VLBI solutions. Decimetric accuracy has been achieved.

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A Data Assimilated Regional Ionosphere Model Using the Total Electron Content from the Korean GPS Network

Journal of the Korean Physical Society ◽

10.3938/jkps.72.826 ◽

2018 ◽

Vol 72 (7) ◽

pp. 826-834 ◽

Cited By ~ 1

Author(s):

Chalachew Kindie Mengist ◽

Yong Ha Kim ◽

Nicholas Ssessanga ◽

Jeong-Heon Kim

Keyword(s):

Total Electron Content ◽

Electron Content ◽

Total Electron ◽

Ionosphere Model ◽

Gps Network

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Improvements to Predictions of the Ionospheric Annual Anomaly by the International Reference Ionosphere Model

10.5194/angeo-2018-97 ◽

2018 ◽

Author(s):

Steven Brown ◽

Dieter Bilitza ◽

Erdal Yiğit

Keyword(s):

Northern Hemisphere ◽

International Reference Ionosphere ◽

Model Data ◽

Iri Model ◽

International Reference ◽

Data Comparison ◽

Ionosphere Model ◽

Model Predictions ◽

One Year ◽

Underlying Processes

Abstract. The annual anomaly is the ionospheric phenomena in which the globally-averaged electron density is greater in January than it is in July. This anomaly causes the ionospheric solsticial variation – a variation with a periodicity of one year that is in-phase with the January solstice – to be more pronounced over the Northern Hemisphere than the Southern Hemisphere. Predictions of the magnitude of annual anomaly using the International Reference Ionosphere (IRI) model have been shown to be unreliable so far. The objective of our study is to investigate model prediction of the magnitude of the annual ionospheric anomaly using new ionospheric indices as inputs in the IRI model. These new indices improve predictions ionospheric variations that differ over the two hemispheres. We present a retrospective analysis of the IRI predictions of the ionospheric daytime annual anomaly and solsticial variation using a model-data comparison with observations from over 40 ionosondes for high, moderate, and low solar cycle conditions. Our results show that there is an overall 33 % underestimation of the magnitude of the annual anomaly when the by the IRI. When the new ionospheric indices as used in the IRI, model predictions underestimate the magnitude of the annual anomaly by 6 %. This indicates an improvement of the model predictions when using the new indices. We show that the underestimation of the annual anomaly by IRI is related to a similar underestimation of the magnitude of the ionospheric solsticial variation over the Northern Hemisphere. Based on our results, we infer that the underlying processes of the annual anomaly must vary across each hemisphere.

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Modification of the solar activity indices in the International Reference Ionosphere IRI and IRI-Plas models due to recent revision of sunspot number time series

Solnechno-Zemnaya Fizika ◽

10.12737/20872 ◽

2016 ◽

Vol 2 (3) ◽

pp. 59-68 ◽

Cited By ~ 6

Author(s):

Тамара Гуляева ◽

Tamara Gulyaeva

Keyword(s):

Time Series ◽

Solar Activity ◽

Sunspot Number ◽

International Reference Ionosphere ◽

Electron Content ◽

Prediction Errors ◽

Solar Cycles ◽

Total Electron ◽

International Reference ◽

Ionospheric Models

The International Reference Ionosphere (IRI) imports global effective ionospheric IG12 index based on ionosonde measurements of the critical frequency foF2 as a proxy of solar activity. Similarly, the global electron content (GEC), smoothed by the sliding 12-months window (GEC12), is used as a solar proxy in the ionospheric and plasmaspheric model IRI-Plas. GEC has been calculated from global ionospheric maps of total electron content (TEC) since 1998 whereas its productions for the preceding years and predictions for the future are made with the empirical model of the linear dependence of GEC on solar activity. At present there is a need to re-evaluate solar and ionospheric indices in the ionospheric models due to the recent revision of sunspot number (SSN2) time series, which has been conducted since 1st July, 2015 [Clette et al., 2014]. Implementation of SSN2 instead of the former SSN1 series with the ionospheric model could increase model prediction errors. A formula is proposed to transform the smoothed SSN212 series to the proxy of the former basic SSN112=R12 index, which is used by IRI and IRI-Plas models for long-term ionospheric predictions. Regression relationships are established between GEC12, the sunspot number R12, and the proxy solar index of 10.7 cm microwave radio flux, F10.712. Comparison of calculations by the IRI-Plas and IRI models with observations and predictions for Moscow during solar cycles 23 and 24 has shown the advantage of implementation of GEC12 index with the IRI-Plas model.

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