Variation of GPS- Tec Measurements of the Year 2014: A Comparative Study with IRI - 2016 Model

Abstract

Total Electron Content (TEC) measured from Global Positioning System (GPS) receivers at latitude of 29.17°N and longitude of 80.62°E in Bardiya and TEC derived from IRI- 2016 model is compared for the year 2014, which is geo- magnetically active year. To find out the reliability of IRI-2016 model, comparative study of GPS- TEC and IRI- TEC is very helpful for the study of TEC variations. In this work diurnal, day to day, month to month and seasonal variations of GPS- TEC and IRI- TEC are analyzed. The comparative study shows that the highest value of VTEC (53 TECU) is found on the day of 61 and over estimation of IRI-TEC over GPS TEC were found from day 151 to day 258. Similarly, months of March and December are the highest and lowest values of VTEC obtained respectively. For monthly variation, IRI-TEC is followed by the pattern of variation with GPS- TEC, where peak value is found to be around 0800 UT to 1100 UT (0145 LT to 0445 LT). The higher values of both GPS- TEC and IRI TEC have been found in spring season, while the lower values are in winter season in case of IRI TEC and partially in summer (before 1000 UT) and winter (after 10UT) in case of GPS TEC. The maximum difference between the value of IRI modeled TEC and GPS TEC has been found to be around 15 TECU, whereas the minimum value is almost around 1 TECU. The correlation between IRI- 2016 modeled TEC and GPS- TEC has been found to be positive (0.57) showing good matching on variations of GPS TEC and IRI-model results.

Climatology of ionosphere over Nepal based on GPS total electron content data from 2008 to 2018

“…In general, the plots show that VTEC is maximum during spring followed by autumn, summer and winter, except for a few cases. Similarly, pre-vious studies of GPS TEC for the year 2014 over Nepal also reported the highest value of VTEC in March and lowest in December, with distinct the seasonal variations and having higher values in spring and lower in the winter season (Ghimire et al, 2020b). During the sunspot minimum years of 2008-2010, there are no semiannual variations in the VTEC, and it also seems that the summer VTEC is as strong as the autumn VTEC.…”

“…The lower atmospheric disturbance also contributes to ionospheric variability (Anderson and Fuller-Rowell, 1999;Prikryal et al, 2010). Numerous periodic and aperiodic variabilities identified in the ionosphere make the impact on the applications involving the radio link between satellites and the ground, which plays vital role in the communication, navigation and surveillance, with important consequences for the reliability and accuracy of the service (Guo et al, 2015). The global positioning system (GPS) is widely used in recent appliances which encounter the largest errors in the path due to disturbed ionospheric free electrons, emphasizing the need to study GPS-TEC variability.…”

“…An analogous study was carried out around the globe using various methods of TEC, such as diurnal, monthly, seasonal and solar cycle and solar activity dependency, e.g. in South Asia (Chauhan et al, 2011;Walker et al, 1994), in South America (Sahai et al, 2007;Natali and Meza, 2011;Akala et al, 2013;de Abreu et al, 2014), over North America (Huo et al, 2009;Perevalova et al, 2010), in Africa (Shimeis et al, 2014;D'ujanga et al, 2012;Ouattara and Fleury, 2011;Zoundi et al, 2012), over Brazil (Venkatesh et al, 2014a(Venkatesh et al, , 2014b(Venkatesh et al, , 2015, over Japan (Zakharenkova et al, 2012;Mansoori et al, 2016) and over China (Guo et al, 2015;Zhao et al, 2007;Liu et al, 2013).…”

Analysis of Tec Variations over Nepal Obtained from GPS Data on Geo-Magnetically Quiet and Disturbed Days of the Year 2015

“…where, , is the mean radius of the earth in; , the ionosphere (effective) height above the earth's surface; Z, the zenith angle; and E, the elevation angle in degrees [7]. Rama Rao et al (2006) [9] observed that the IPP (Ionospheric Pierce Point) attitude of 350 km is valid for the satellite elevation angle greater than 20°. A GPS receiver can lock the signal of more than one satellite at a time at different angle of elevation from the receivers.…”

“…In past years, GPS has become an important tool to study ionospheric character [5 6 7 8]. Due to increment in demand of GPS-based navigation appliances in satellites, aircrafts and other transportations, the study of TEC is heightened [9]. The GPS-TEC is the total number of electrons in a vertical column of 1 cross-section from the height of the GPS satellite (~ 20,000 km) to the receiver on the ground.…”