scholarly journals Seasonal and solar activity variations of the Weddell Sea Anomaly observed in the TOPEX total electron content measurements

2009 ◽  
Vol 114 (A4) ◽  
pp. n/a-n/a ◽  
Author(s):  
G. Jee ◽  
A. G. Burns ◽  
Y.-H. Kim ◽  
W. Wang
Keyword(s):  
Solar Activity ◽  
Total Electron Content ◽  
Weddell Sea ◽  
Electron Content ◽  
Total Electron ◽  
Weddell Sea Anomaly

scholarly journals Spatial and Temporal Variations of Polar Ionospheric Total Electron Content over Nearly Thirteen Years

Sensors ◽  
2020 ◽  
Vol 20 (2) ◽  
pp. 540 ◽  
Author(s):  
Hui Xi ◽  
Hu Jiang ◽  
Jiachun An ◽  
Zemin Wang ◽  
Xueyong Xu ◽  
...  
Keyword(s):  
Solar Activity ◽  
Total Electron Content ◽  
Geomagnetic Storms ◽  
Weddell Sea ◽  
The Arctic ◽  
Electron Content ◽  
Spherical Cap ◽  
Total Electron ◽  
Ionospheric Total Electron Content ◽  
The Antarctic

It is of great significance for the global navigation satellite system (GNSS) service to detect the polar ionospheric total electron content (TEC) and its variations, particularly under disturbed ionosphere conditions, including different phases of solar activity, the polar day and night alternation, the Weddell Sea anomaly (WSA) as well as geomagnetic storms. In this paper, four different models are utilized to map the ionospheric TEC over the Arctic and Antarctic for about one solar cycle: the polynomial (POLY) model, the generalized trigonometric series function (GTSF) model, the spherical harmonic (SH) model, and the spherical cap harmonic (SCH) model. Compared to other models, the SCH model has the best performance with ±0.8 TECU of residual mean value and 1.5–3.5 TECU of root mean square error. The spatiotemporal distributions and variations of the polar ionospheric TEC are investigated and compared under different ionosphere conditions in the Arctic and Antarctic. The results show that the solar activity significantly affects the TEC variations. During polar days, the ionospheric TEC is more active than it is during polar nights. In polar days over the Antarctic, the maximum value of TEC always appears at night in the Antarctic Peninsula and Weddell Sea area affected by the WSA. In the same year, the ionospheric TEC of the Antarctic has a larger amplitude of annual variation than that of the TEC in the Arctic. In addition, the evolution of the ionization patch during a geomagnetic storm over the Antarctic can be clearly tracked employing the SCH model, which appears to be adequate for mapping the polar TEC, and provides a sound basis for further automatic identification of ionization patches.

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.

Observations of ionospheric TEC peaked structures from Global Ionosphere Maps

2020 ◽  
Author(s):  
Tsung-Che Tsai ◽  
Hau-Kun Jhuang ◽  
Lou-Chuang Lee ◽  
Yi-Ying Ho
Keyword(s):  
Local Time ◽  
Geomagnetic Latitude ◽  
Weddell Sea ◽  
Electron Content ◽  
Destructive Interference ◽  
Total Electron ◽  
Weddell Sea Anomaly ◽  
Time Structures ◽  
Time Frames ◽  
Wave Modes

<p>The total electron content (TEC) data from Global Ionosphere Maps provide a global TEC map in the region between latitude 87.5°S to 87.5°N, and longitude 180°W to 180°E. The TEC data in geographic coordinates are first transformed into geomagnetic coordinates through Altitude-Adjusted Corrected Geomagnetic Model (AACGM). We then use 2-dimensional (longitudinal, 180°W-180°E and time, 10 days) Fourier transform (FT) of TEC variations along different geomagnetic latitude to obtain all wave modes in both UT (universal time) and LT (local time) frames for the period from November 18, 2002 to October 15, 2014. The summation of contributing wave modes at a given local time provides the longitudinal variation of the associated zonal waves. The phases of wave modes lead to a constructive or destructive interference of contributing zonal wave, which gives different structures at different local time. These local time structures include Weddell Sea Anomaly (WSA), Southern Atlantic Anomaly (SAA), and Four-peaked structure. The dependence of the peaked structures on latitudinal, seasonal, and solar activity is studied.</p>

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 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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