scholarly journals Variations of total electron content over Serbia during the increased solar activity period in 2013 and 2014

2016 ◽  
Vol 60 (04) ◽  
pp. 734-744
Author(s):  
Dragan Blagojevic ◽  
Miljana Todorovic Drakul ◽  
Oleg Odalovic ◽  
Sanja Grekulovic ◽  
Jovan Popovic ◽  
...  
Keyword(s):  
Solar Activity ◽  
Total Electron Content ◽  
Activity Period ◽  
Electron Content ◽  
Total Electron ◽  
Solar Activity Period

scholarly journals Evaluating the Performance of IRI-2016 Using GPS-TEC Measurements over the Equatorial Region

Atmosphere ◽  
2021 ◽  
Vol 12 (10) ◽  
pp. 1243
Author(s):  
Nouf Abd Elmunim ◽  
Mardina Abdullah ◽  
Siti Aminah Bahari
Keyword(s):  
Solar Activity ◽  
Early Morning ◽  
Equatorial Region ◽  
Activity Period ◽  
High Solar Activity ◽  
Electron Content ◽  
Dual Frequency ◽  
Iri Model ◽  
Total Electron ◽  
Solar Activity Period

Total electron content (TEC) is an important parameter in the ionosphere that is extensively used to study the variability of the ionosphere as it significantly affects radio wave propagations, causing delays on GPS signals. Therefore, evaluating the performance of ionospheric models is crucial to reveal the variety of ionospheric behaviour in different solar activity periods during geomagnetically quiet and disturbed periods for further improvements of the IRI model performance over the equatorial region. This research aimed to investigate the variations of ionospheric VTEC and observe the improvement in the performance of the IRI-2016 (IRI-2001, IRI01-corr, and NeQuick). The IRI-2016 was evaluated with the IRI-2012 using NeQuick, IRI-2001, and IRI01-corr topside electron density options. The data were obtained using a dual-frequency GPS receiver installed at the Universiti Utara Malaysia Kedah (UUMK) (geographic coordinates 4.62° N–103.21° E, geomagnetic coordinates 5.64° N–174.98° E), Mukhtafibillah (MUKH) (geographic coordinates 6.46° N–100.50° E, geomagnetic coordinates 3.32° S–172.99° E), and Tanjung Pengerang (TGPG) (geographic coordinates 1.36° N–104.10°E, geomagnetic coordinates 8.43° S–176.53° E) stations, during ascending to high solar activity at the geomagnetically quiet and disturbed periods in October 2011, March 2012, and March 2013. The maximum hourly ionospheric VTEC was observed during the post-noon time, while the minimum was during the early morning time. The ionospheric VTEC modelled by IRI-2016 had a slight improvement from the IRI-2012. However, the differences were observed during the post-noon and night-time, while the modelled VTEC from both IRI models were almost similar during the early morning time. Regarding the daily quiet and disturbed period’s prediction capability of the IRI-2016 and IRI-2012, IRI-2016 gave better agreement with the measured VTEC. The overall results showed that the model’s prediction performance during the high solar activity period in 2013 was better than the one during the ascending solar activity period. The results of the comparison between IRI-2016 and IRI-2012 in high solar activity exhibited that during quiet periods, all the IRI models showed better agreement with the measured VTEC compared to the disturbed periods.

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 TEC variations during low solar activity period (2005–2007) near the Equatorial Ionospheric Anomaly Crest region in India

2009 ◽  
Vol 27 (3) ◽  
pp. 1047-1057 ◽  
Author(s):  
Mala S. Bagiya ◽  
H. P. Joshi ◽  
K. N. Iyer ◽  
M. Aggarwal ◽  
S. Ravindran ◽  
...  
Keyword(s):  
Solar Activity ◽  
Geomagnetic Storm ◽  
Activity Period ◽  
Electron Content ◽  
Ionospheric Storm ◽  
Equatorial Anomaly ◽  
Total Electron ◽  
Short Period ◽  
Storm Effect ◽  
Solar Activity Period

Abstract. The dual frequency signals from the GPS satellites recorded at Rajkot (22.29° N, 70.74° E, Geographic, 14.03° N Geomagnetic) near the Equatorial ionization anomaly crest in India have been analyzed to study the ionospheric variations in terms of Total Electron Content (TEC) for the low solar activity period from April 2005 to December 2007. In this study, we describe the diurnal and seasonal variations of TEC, solar activity dependence of TEC and effects of a space weather related event, a geomagnetic storm on TEC. The diurnal variation of TEC shows pre-dawn minimum for a short period of time, followed by a steep early morning increase and then reaches maximum value between 14:00 LT and 16:00 LT. The mean diurnal variations during different seasons are brought out. It is found that TEC at Rajkot is at its maximum during Equinoctial months (March, April, September, October), and minimum during the Winter months (November, December, January, February), with intermediate values during Summer months (May, June, July, August), showing a semi annual variation. TEC values have been decreasing since 2005, onwards showing positive correlation with solar activity. TEC variations during the geomagnetic storm commencing 24 August 2005 with Dst=−216 nT are analysed. TEC shows a positive ionospheric storm effect on the first day of the storm and negative ionospheric storm effect on the next day. The equatorial Electrojet control on the development of the equatorial anomaly is also demonstrated.

scholarly journals Study of GPS derived Total Electron Content and Scintillation Index variations over Indian Arctic and Antarctic stations

2013 ◽  
Vol 5 (2) ◽  
pp. 255-264 ◽  
Author(s):  
P. Bhawre ◽  
A. K. Gwal ◽  
A. A. Mansoori ◽  
P. A. Khan
Keyword(s):  
Total Electron Content ◽  
Winter Season ◽  
Scintillation Index ◽  
Activity Period ◽  
Electron Content ◽  
Gps Receiver ◽  
Dual Frequency ◽  
Total Electron ◽  
Ionospheric Variability ◽  
Solar Activity Period

In the present study we have investigated the monthly and seasonal variability of total electron content (TEC) and amplitude scintillation index (S4) over two Indian polar stations Maitri (Antarctic) and Ny-Alesund (Arctic), during the low solar activity period 2008. We have used the Novatel’s dual frequency GPS receiver GSV4004A to accomplish this study. From our analysis we observed that TEC achieves its highest values during the months of November and December while during the month of May and June the lowest values of TEC were recorded at Maitri station. Similarly during summer season the highest values of TEC are recorded while in winter season lowest values of TEC are observed. The scintillations that occurred during the year 2008 at Maitri as well as at Ny-Alesund were generally found to be of weak type (S4?0.1), although few cases of moderate (S4?0.3) and strong (S4?0.5) scintillation were also observed. The occurrence characteristics of scintillations showed that maximum scintillations at Maitri occur during the month of July and August while least scintillations occur during the month of January and February. This type of ionospheric variability can be explained on the basis of solar irradiance at Polar Regions.Keywords: Total electron content; Scintillation index; Polar ionosphere.© 2013 JSR Publications. ISSN: 2070-0237 (Print); 2070-0245 (Online). All rights reserved.doi: http://dx.doi.org/10.3329/jsr.v5i2.12724        J. Sci. Res. 5 (2), 255-264 (2013)

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 GPS Total Electron Content measurements at low latitudes in Brazil for low solar activity

2004 ◽  
Vol 43 (1) ◽  
pp. 129-137
Author(s):  
Aracy Mendes da Costa ◽  
J. Williams Vilas Boas ◽  
Edvaldo S. Da Fonseca Junior
Keyword(s):  
Solar Activity ◽  
Total Electron Content ◽  
Electron Content ◽  
Total Electron ◽  
Low Latitudes

Se calcularon las variaciones del número total de electrones en la ionosfera (TEC) usando datos de GPS, obtenidos en la estación de baja latitud de Presidente Prudente, Brasil (22.1° S; 51.4° W) en 1997, un periodo de baja actividad solar. Se presentan dos promedios horarios durante este periodo. Se discuten las variaciones diarias, estacionales, debidas a la actividad solar y la Anomalía Ecuatorial. Los promedios diurnos de TEC se comparan con las predicciones del modelo IRI-95 para los meses de los equinoccios y los solsticios y se muestra que IRI-95 sistemáticamente sobreestima los valores observados. Los aumentos prenocturnos de TEC se observaron durante todo el año excepto en mayo y junio. Los valores de TEC medidos reproducen la misma tendencia general de los valores TEC observados en Cachoeira Paulista, Brasil (22.5° S; 45° W). El efecto "fuente" parece ser más efectivo en Presidente Prudente debido a su menor latitud magnética. La correlación entre los valores experimentales de TEC y el flujo solar durante la baja actividad (62 < F10.7 < 116 unidades de flujo) enfatiza que el modelo IRI para bajas latitudes y periodos de baja actividad solar es inadecuado. Los resultados aquí presentados son los primeros obtenidos usando la técnica TEC-GPS sobre la parte suroeste de Brasil.

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