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

Natali, María Paula; Meza, Amalia

doi:10.5194/angeo-29-865-2011

Cited by 29 publications

(24 citation statements)

References 29 publications

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“…Further, we observed opposite latitudinal asymmetry among annual and semiannual variations for three GNSS stations. Zhao et al (2008) and Natali and Meza (2011) also reported the similar findings for high solar activity year. The results in Table 2 and " Fig.…”

Section: Resultssupporting

confidence: 72%

Analysis of local ionospheric variability based on SVD and MDS at low-latitude GNSS stations

Dabbakuti

Kanchumarthi

2016

Earth Planet Sp

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Investigation of ionospheric anomalies during equatorial and low latitude is of major concern for modeling and global navigation satellite system (GNSS) applications. Total electron content (TEC) varies with the ionospheric conditions, which will lead to the errors in the global positioning system (GPS) measurements. It is therefore a method that is necessary to characterize the ionospheric anomalies for satellite-based navigation systems. In this study, characterization of ionospheric variations based on the singular value decomposition (SVD) and classical multidimensional scaling (MDS) methods was studied. The yearly and daily variations are decomposed from the GPS-TEC, international reference ionosphere (IRI) 2007 and IRI 2012 models TEC over the three low-latitude GNSS stations located at Koneru Lakshmaiah University (KLU-Guntur), Hyderabad and Bangalore, respectively. From the results, it is found that there is a strong correlation between GPS-TEC and IRI models. The correlation coefficient for the first three singular values is more than 0.86. From this, it is possible to reconstruct more than 85 % of the variability contained in global GPSderived VTEC data (for year 2013) by using only the first three modes. The semiannual variation has maximum value during March-April and September-October and has minimum value during June-July. It is observed that the annual variations have maximum value in summer and minimum value in winter, and the amplitudes decrease with increasing latitude. Further, opposite latitudinal asymmetry among annual and semiannual variations for three GNSS stations is noticed. SVD and MDS methods clearly show time-varying characteristics and the absence of the winter anomaly at low-latitude GNSS stations.

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Section: Resultssupporting

confidence: 72%

Analysis of local ionospheric variability based on SVD and MDS at low-latitude GNSS stations

Dabbakuti

Kanchumarthi

2016

Earth Planet Sp

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“…[7 and 9] both worked on TEC at stations (Ilorin, Nigeria and India) in low latitudes during the low solar activity period, and they showed that the diurnal characteristics of TEC depend on season, solar activity, geomagnetic activity, and latitude. [7, 8 and 13] showed that the seasonal variations in vertical TEC are higher during the equinox than the solstice during low solar activity, while [14] showed that the story was the same at high solar activity using different stations. Quantitative study of transient variations in GPS TEC, involving simultaneously measured data from multiple stations in Nigeria, to show the diurnal and the seasonal variation of the GPS-TEC data has been done by several authors: [9, 10, 15 -17].…”

Section: Introductionmentioning

confidence: 99%

Seasonal variations of the Vertical Total Electron Content (VTEC) of the ionosphere at the GNSS cor station (SEERL) UNIBEN and three other cors stations in Nigeria

Elemo

Ehigiator²,

Ehigiator-Irughe³

2018

Nig. J. Tech.

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The complex environment of the Sun-Earth, which resulted in the spatial and temporal variations of the ionosphere leads to different kinds of effects on human technologies. Man's continuous increasing utilization of space technologies in addressing it's immediate and future needs demand quality research of the space environments, to understand the physics of the interaction of the environment with systems (both space and earth bound), and to develop methods of mitigating the environmental effects. This is one of the reasons Center of Atmospheric Research

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“…However, there is a lack of information for the longitudinal variations of the neutral density of N2 during nighttime. A few studies revealed that the annual and semiannual variations of the nighttime electron density are absent at midlatitudes in both hemispheres (e.g., Ma et al, 2003;Natali and Meza, 2011), which suggests the neutral composition may have a lesser effect on the ionospheric electron density longitudinal pattern during nighttime than it has during daytime. In the present study, the maximum relative longitudinal difference occurs around midnight in summer, which is associated with the occurrence time of maximum upward plasma drifts.…”

Section: The Wsa and The Electron Density Longitudinal Differencementioning

confidence: 99%

Seasonal dependence of the longitudinal variations of nighttime ionospheric electron density and equivalent winds at southern midlatitudes

Luan

Dou

2013

Ann. Geophys.

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Abstract. It has been indicated that the observed Weddell Sea anomaly (WSA) appeared to be an extreme manifestation of the longitudinal variations in the Southern Hemisphere, since the WSA is characterized by greater evening electron density than the daytime density in the region near the Weddell Sea. In the present study, the longitudinal variations of the nighttime F2-layer peak electron density at southern midlatitudes are analyzed using the observations of the Constellation Observing System for Meteorology, Ionosphere, and Climate (COSMIC) satellites between 2006 and 2008. It is found that significant longitudinal difference (> 150 %) relative to the minimum density at each local time prevails in all seasons, although the WSA phenomenon is only evident in summer under this solar minimum condition. Another interesting feature is that in summer, the maximum longitudinal differences occur around midnight (∼ 23:00-00:00 LT) rather than in the evening (19:00-21:00 LT) in the evening, when the most prominent electron density enhancement occurs for the WSA phenomenon. Thus the seasonallocal time patterns of the electron density longitudinal variations during nighttime at southern midlatitudes cannot be simply explained in terms of the WSA. Meanwhile, the variations of the geomagnetic configuration and the equivalent magnetic meridional winds/upward plasma drifts are analyzed to explore their contributions to the longitudinal variations of the nighttime electron density. The maximum longitudinal differences are associated with the strongest windinduced vertical plasma drifts after 21:00 LT in the Western Hemisphere. Besides the magnetic declination-zonal wind effects, the geographic meridional winds and the magnetic inclination also have significant effects on the upward plasma drifts and the resultant electron density.

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

Cited by 29 publications

References 29 publications

Analysis of local ionospheric variability based on SVD and MDS at low-latitude GNSS stations

Analysis of local ionospheric variability based on SVD and MDS at low-latitude GNSS stations

Seasonal variations of the Vertical Total Electron Content (VTEC) of the ionosphere at the GNSS cor station (SEERL) UNIBEN and three other cors stations in Nigeria

Seasonal dependence of the longitudinal variations of nighttime ionospheric electron density and equivalent winds at southern midlatitudes

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