Abstract
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 GPS-derived 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.
Highlights
Ionosphere is that part of upper atmosphere, extending from a height of 50 to 2000 km above the earth’s surface
An attempt is made to describe ionospheric variability, accounting for daily, yearly, seasonal and solar variations of equatorial ionospheric anomaly (EIA) in global positioning system (GPS)-total electron content (TEC) based on singular value decomposition (SVD) and classical multidimensional scaling (MDS) methods over low-latitude global navigation satellite system (GNSS) stations ranging from 12.97°N to 17.41°N (Bangalore, KLU-Guntur and Hyderabad) during 24th solar cycle for the year 2013
GPS-TEC and international reference ionosphere (IRI) model data for the year 2013 are considered to study the ionospheric variability for three geographic locations
Summary
Ionosphere is that part of upper atmosphere, extending from a height of 50 to 2000 km above the earth’s surface. An attempt is made to describe ionospheric variability, accounting for daily, yearly, seasonal and solar variations of equatorial ionospheric anomaly (EIA) in global positioning system (GPS)-TEC based on singular value decomposition (SVD) and classical multidimensional scaling (MDS) methods over low-latitude GNSS stations ranging from 12.97°N to 17.41°N (Bangalore, KLU-Guntur and Hyderabad) during 24th solar cycle for the year 2013. Data and location Ionospheric characteristics for the year 2013 are considered for the three low-latitude GNSS stations in India, located at KLU-Guntur (16.44°N, 80.62°E), Hyderabad (17.41°N, 78.52°E) and Bangalore (12.97°N, 77.59°E), respectively.
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