GPS-TEC Variation during Low to High Solar Activity Period (2010-2014) under the Northern Crest of Indian Equatorial Ionization Anomaly Region

Abstract

The measurements of ionospheric TEC (total electron content) are conducted at a low latitude Indian station Surat (21.16˚N, 72.78˚E Geog.), which lies under the northern crest of the equatorial anomaly in Indian region. The data obtained are for a period of five years from low to high solar activity (2010-2014) using GPS (Global Positioning System) receiver. In this study, we report the diurnal and seasonal variation of GPS-TEC, dependence of GPS-TEC with solar activity, geomagnetic condition and EEJ strength. From the seasonal analysis, it is found that greater values of the GPS-TEC are observed during equinox season followed by winter and summer. The appearance (in the year 2011 and 2014) and disappearance (in the year 2010 and 2012) of "winter anomaly" have been observed at the station. From the correlation of GPS-TEC with different solar indices, i.e. solar EUV flux, F10.7 cm solar radio flux and Zurich sunspot number (SSN), it is concluded that the solar index EUV flux is a better controller of GPS-TEC, compared to F10.7 cm and SSN. Further, it is observed that there is no effect of rising solar activity on correlation. Moreover, the percentage variability of GPS-TEC and the standard deviation of GPS-TEC obtained for quiet and disturbed days show that dependence of GPS-TEC on geomagnetic condition is seasonal. Also, there is a positive correlation observed between GPS-TEC and EEJ strength.

Statistics of GPS TEC at the northern EIA crest region of the Indian subcontinent during the solar cycle 24 (2013-2018): comparison with IRI-2016 and IRI-2012 models

“…The radiations and charged particles, from the Sun, are the main sources of incoming energy or insolation on the Earth (Patel et al 2017b). In the upper atmosphere of the earth, the effect of solar radiations is measured in terms of solar indices like i) Zurich sunspot number (SSN), ii) 10.7 cm solar radio flux (F10.7) which is an extent of the intensity of solar radio emission at the reciprocal of the period of 2800 MHz and iii) The solar extreme ultraviolet (EUV) flux.…”

“…So as compared to SSN and F10.7, the solar index EUV flux is a better indicator of GPS-TEC for high to moderate solar activity period (2013)(2014)(2015)(2016)(2017). The ionization due to solar radiation and growth of electron density due to transport, control the electron density in the equatorial and low latitude regions Patel et al (2017b). During day-time period, the solar radiation mainly controls the electron density at equator.…”

“…hour of maximum TEC) appeared 1.00 hr later than the actual peak time in winter-2010winter- , summer-2011winter- , and Equinox-2010winter- , 2012 while for the summer season the IRI-TEC estimated the TEC well for all the years. Patel et al (2017b) also investigated the variation of GPS-TEC during the period 2010-2014 and greater values of the GPS-TEC were observed during equinox season followed by winter and summer. The appearance (in 2011 and 2014) and disappearance (in 2010 and 2012) of winter anomaly were observed at this station.…”

Total electron content (TEC) seasonal variability under fluctuating activity, from 2000 to 2002, at Niamey station

“…The variability of ionospheric parameters such as TEC, in the equatorial region, has already been reviewed by different authors (Ouattara, 2009;Dabas et al, 2003;Zoundi et al, 2013;Suranya et al, 2015;Hajra et al, 2016;D'ujanga et al, 2017;Ouattara et al, 2017;Patel et al, 2017;Ogwala et al, 2018). Ouattara (2009), Zoundi et al (2013) and Ouattara et al (2017) have investigated TEC variability at Niamey station during various solar events.…”

Latitudinal variation of ionospheric TEC at Northern Hemispheric region

“…Apart from latitudinal variation a number of researchers have investigated morphological features of TEC such as the diurnal, monthly, seasonal and solar activity variation using ES1003 mahesh parwani et al: latitudinal variation ES1003 various techniques around the globe e.g. in Africa, [D'ujanga et al, 2012;Fayose et al, 2012;Oron et al, 2013;Ouattara and Fleury, 2011;Zoundi et al, 2012] in South East Asia [Walker et al, 1994], in South America [Akala et al, 2013b;de Abreu et al, 2014;Natali and Meza, 2011;Sahai et al, 2007], over China [Liu et al, 2013;Zhao et al, 2007], over North America [Huo et al, 2009;Perevalova et al, 2010], over Japan [Mansoori et al, 2016;Zakharenkova et al, 2012], over Brazil [Venkatesh et al, 2014a[Venkatesh et al, , 2014b[Venkatesh et al, , 2015] and many more. Ionospheric TEC variations have been investigated in the Indian region also at Surat [Chauhan et al, 2011;Karia and Pathak, 2011], Agra [Nilesh et al, 2017] and many other.…”