scholarly journals Empirical models of Total Electron Content based on functional fitting over Taiwan during geomagnetic quiet condition

2009 ◽  
Vol 27 (8) ◽  
pp. 3321-3333 ◽  
Author(s):  
Y. Kakinami ◽  
C. H. Chen ◽  
J. Y. Liu ◽  
K.-I. Oyama ◽  
W. H. Yang ◽  
...  
Keyword(s):  
Solar Activity ◽  
Total Electron Content ◽  
Empirical Models ◽  
Electron Content ◽  
Total Electron ◽  
Quiet Condition ◽  
Functional Fitting ◽  
Using Data ◽  
First Time ◽  
Fitting Model

Abstract. Empirical models of Total Electron Content (TEC) based on functional fitting over Taiwan (120° E, 24° N) have been constructed using data of the Global Positioning System (GPS) from 1998 to 2007 during geomagnetically quiet condition (Dst>−30 nT). The models provide TEC as functions of local time (LT), day of year (DOY) and the solar activity (F), which are represented by 1–162 days mean of F10.7 and EUV. Other models based on median values have been also constructed and compared with the models based on the functional fitting. Under same values of F parameter, the models based on the functional fitting show better accuracy than those based on the median values in all cases. The functional fitting model using daily EUV is the most accurate with 9.2 TECu of root mean square error (RMS) than the 15-days running median with 10.4 TECu RMS and the model of International Reference Ionosphere 2007 (IRI2007) with 14.7 TECu RMS. IRI2007 overestimates TEC when the solar activity is low, and underestimates TEC when the solar activity is high. Though average of 81 days centered running mean of F10.7 and daily F10.7 is often used as indicator of EUV, our result suggests that average of F10.7 mean from 1 to 54 day prior and current day is better than the average of 81 days centered running mean for reproduction of TEC. This paper is for the first time comparing the median based model with the functional fitting model. Results indicate the functional fitting model yielding a better performance than the median based one. Meanwhile we find that the EUV radiation is essential to derive an optimal TEC.

scholarly journals Regional reference total electron content model over Japan based on neural network mapping techniques

2007 ◽  
Vol 25 (12) ◽  
pp. 2609-2614 ◽  
Author(s):  
T. Maruyama
Keyword(s):  
Neural Network ◽  
Solar Activity ◽  
Total Electron Content ◽  
Reference Model ◽  
Activity Period ◽  
Electron Content ◽  
Total Electron ◽  
Grid Points ◽  
Using Data ◽  
Regional Reference

Abstract. A regional reference model of total electron content (TEC) was constructed using data from the GPS Earth Observation Network (GEONET), which consists of more than 1000 Global Positioning System (GPS) satellite receivers distributed over Japan. The data covered almost one solar activity period from April 1997 to June 2007. First, TECs were determined for 32 grid points, expanding from 27 to 45° N in latitude and from 127 to 145° E in longitude at 15-min intervals. Secondly, the time-latitude variation averaged over three days was determined by using the surface harmonic functional expansion. The coefficients of the expansion were then modeled by using a neural network technique with input parameters of the season (day of the year) and solar activity (F10.7 index and sunspot number). Thus, two-dimensional TEC maps (time vs. latitude) can be obtained for any given set of solar activity and day of the year.

scholarly journals Global equivalent slab thickness model of the Earth’s ionosphere

2021 ◽  
Author(s):  
Norbert Jakowski ◽  
Mohammed Mainul Hoque
Keyword(s):  
Solar Activity ◽  
Electron Density ◽  
Total Electron Content ◽  
Local Time ◽  
Slab Thickness ◽  
Electron Content ◽  
Night Time ◽  
Total Electron ◽  
First Time ◽  
Model Approach

The shape of the vertical electron density profile is a result of production, loss and transportation of plasma in the Earth’s ionosphere. Therefore, the equivalent slab thickness of the ionosphere that characterizes the width of vertical electron density profiles is an important parameter for a better understanding of ionospheric processes under regular as well as under perturbed conditions. The equivalent slab thickness is defined by the ratio of the vertical total electron content over the peak electron density and is therefore easy to compute by utilizing powerful data sources nowadays available thanks to ground and space based GNSS techniques. Here we use peak electron density data from three low earth orbiting (LEO) satellite missions, namely CHAMP, GRACE and FORMOSAT-3/COSMIC, as well as total electron content data obtained from numerous GNSS ground stations. For the first time, we present a global model of the equivalent slab thickness (Neustrelitz equivalent Slab Thickness Model – NSTM). The model approach is similar to a family of former model approaches successfully applied for Total Electron Content (TEC), peak electron density NmF2 and corresponding height hmF2 at DLR. The model description focuses on an overall view of the behaviour of the equivalent slab thickness as a function of local time, season, geographic/geomagnetic location and solar activity on a global scale. In conclusion, the model agrees quite well with the overall observation data within a RMS range of 70 km. There is generally a good correlation with solar heat input that varies with local time, season and level of solar activity. However, under non-equilibrium conditions, plasma transport processes dominate the behaviour of the equivalent slab thickness. It is assumed that night-time plasmasphere-ionosphere coupling causes enhanced equivalent slab thickness values like the pre-sunrise enhancement. The overall fit provides consistent results with the mid-latitude bulge (MLB) of the equivalent slab thickness, described for the first time in this paper. Furthermore, the model recreates quite well ionospheric anomalies such as the Night-time Winter Anomaly (NWA) which is closely related to the Mid-latitude Summer Night Anomaly (MSNA) like the Weddell Sea Anomaly (WSA) and Okhotsk Sea Anomaly (OSA). Further model improvements can be achieved by using an extended model approach and considering the particular geomagnetic field structure.

scholarly journals A New Global Total Electron Content Empirical Model

2019 ◽  
Vol 11 (6) ◽  
pp. 706 ◽  
Author(s):  
Jiandi Feng ◽  
Baomin Han ◽  
Zhenzhen Zhao ◽  
Zhengtao Wang
Keyword(s):  
Total Electron Content ◽  
Empirical Model ◽  
Single Point ◽  
Empirical Models ◽  
Electron Content ◽  
International Gnss Service ◽  
Prediction Ability ◽  
Total Electron ◽  
Grid Model ◽  
Grid Points

Research on total electron content (TEC) empirical models is one of the important topics in the field of space weather services. Global TEC empirical models based on Global Ionospheric Maps (GIMs) TEC data released by the International GNSS Service (IGS) have developed rapidly in recent years. However, the accuracy of such global empirical models has a crucial restriction arising from the non-uniform accuracy of IGS TEC data in the global scope. Specifically, IGS TEC data accuracy is higher on land and lower over the ocean due to the lack of stations in the latter. Using uneven precision GIMs TEC data as a whole for model fitting is unreasonable. Aiming at the limitation of global ionospheric TEC modelling, this paper proposes a new global ionospheric TEC empirical model named the TECM-GRID model. The model consists of 5183 sections, corresponding to 5183 grid points (longitude 5°, latitude 2.5°) of GIM. Two kinds of single point empirical TEC models, SSM-T1 and SSM-T2, are used for TECM-GRID. According to the locations of grid points, the SSM-T2 model is selected as the sub-model in the Mid-Latitude Summer Night Anomaly (MSNA) region, and SSM-T1 is selected as the sub-model in other regions. The fitting ability of the TECM-GRID model for modelling data was tested in accordance with root mean square (RMS) and relative RMS values. Then, the TECM-GRID model was validated and compared with the NTCM-GL model and Center for Orbit Determination in Europe (CODE) GIMs at time points other than modelling time. Results show that TECM-GRID can effectively describe the Equatorial Ionization Anomaly (EIA) and the MSNA phenomena of the ionosphere, which puts it in good agreement with CODE GIMs and means that it has better prediction ability than the NTCM-GL model.

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

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.

Equatorial total electron content (TEC) at low and high solar activity

2009 ◽  
Vol 43 (11) ◽  
pp. 1757-1761 ◽  
Author(s):  
O.K. Obrou ◽  
M.N. Mene ◽  
A.T. Kobea ◽  
K.Z. Zaka
Keyword(s):  
Solar Activity ◽  
Total Electron Content ◽  
High Solar Activity ◽  
Electron Content ◽  
Total Electron

scholarly journals Annual and semiannual variations of vertical total electron content during high solar activity based on GPS observations

2011 ◽  
Vol 29 (5) ◽  
pp. 865-873 ◽  
Author(s):  
M. P. Natali ◽  
A. Meza
Keyword(s):  
Solar Activity ◽  
Total Electron Content ◽  
Principal Component ◽  
High Solar Activity ◽  
Electron Content ◽  
Vertical Total Electron Content ◽  
Total Electron ◽  
Ionospheric Variability ◽  
Low Latitudes ◽  
Sudden Decrease

Abstract. Annual, semiannual and seasonal variations of the Vertical Total Electron Content (VTEC) have been investigated during high solar activity in 2000. In this work we use Global IGS VTEC maps and Principal Component Analysis to study spatial and temporal ionospheric variability. The behavior of VTEC variations at two-hour periods, at noon and at night is analyzed. Particular characteristics associated with each period and the geomagnetic regions are highlighted. The variations at night are smaller than those obtained at noon. At noon it is possible to see patterns of the seasonal variation at high latitude, and patterns of the semiannual anomaly at low latitudes with a slow decrease towards mid latitudes. At night there is no evidence of seasonal or annual anomaly for any region, but it was possible to see the semiannual anomaly at low latitudes with a sudden decrease towards mid latitudes. In general, the semiannual behavior shows March–April equinox at least 40 % higher than September one. Similarities and differences are analyzed also with regard to the same analysis done for a period of low solar activity.

scholarly journals Global distribution of GPS losses of phase lock and total electron content slips during the 2005 May 15 and the 2003 November 20 magnetic storms

2015 ◽  
Vol 1 (4) ◽  
pp. 58-65 ◽  
Author(s):  
Юрий Ясюкевич ◽  
Yury Yasyukevich ◽  
Эльвира Астафьева ◽  
Elvira Astafyeva ◽  
Илья Живетьев ◽  
...  
Keyword(s):  
Total Electron Content ◽  
Background Level ◽  
Auroral Oval ◽  
Magnetic Storms ◽  
Electron Content ◽  
High Latitudes ◽  
Total Electron ◽  
Phase Lock ◽  
Using Data ◽  
Worldwide Network

Using data of worldwide network of GPS receivers we investigated losses of GPS phase lock (LoL) during two strong magnetic storms. At fundamental L1 frequency, LoL density is found to increase up to 0.25 % and at L2 frequency the increase is up to 3 %. This is several times as much compared with the background level. During the 2003 November 20 magnetic storm, the number of total electron content (TEC) slips exceeded the background level ~50 times. During superstorms, the most number of GPS LoL is observed at low and high latitudes. At the same time, the area of numerous TEC slips correspond to auroral oval boundaries.

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