Comparison of VTEC from GPS and IRI-2007, IRI-2012 and IRI-2016 over Sukkur Pakistan

Wavelet analysis based VTEC variability over mid-latitude region Sukkur, Pakistan and its comparison with IRI models during 2019-2020

“…The GPS VTEC deviation is higher from the IRI-2007 and the IRI-2012 predicted VTEC, because above 2,000 Km, the plasmaspheric electron content density exists and both of these empirical models are not capable of contemplating the plasmaspheric component (Ezquer et al, 2018). For the mid-latitude region, Shahzad et al (2021) also noted a similar pattern of greater VTEC between March and April and a less deviation in the month of November and December.…”

“…This study compares the retrieved VTEC from various models and calculated GPS VTEC from Sukkur Station for the 2019-2020 period. A useful way to depict, evaluate, and explain the overall conduct of the near-Earth thermal plasma is to use the complete ionospheric electron thickness profile to obtain VTEC (Froń et al, 2020;Shahzad et al, 2021).…”

“…To evaluate diurnal and seasonal variation patterns of VTEC, several types of research have been attempted for different regions by using measured and modelled VTEC values. Such analyses show the night-time VTEC is lower than daytime, while the observed highest VTEC values are about the time of noon and values observed during solstices are lower than equinox season (Bhuyan & Borah 2007;Kumar et al, 2015;Mukesh et al, 2018;Shahzad et al, 2021). during 2009-2011 was determined when compared with Kenya's measured GPS during this period (Olwendo et al, 2013).…”

“…The free electrons in the ionosphere cause the time delay in signal propagation. The magnitude of the ionosphere's phase advance or group delay on satellite radio transmission increases with the TEC enhancement but is inversely proportional to the frequency square (Shahzad et al, 2021). The ionosphere has a dispersive structure, due to which GPS signals which are electromagnetic signals, suffer time delay and advancement in modulated codes and carrier phase, respectively while passing and hence receivers placed on grounds may not get signals on listed time (Ioannides & Strangeways, 2000).…”

“…Several studies have been reported about model predicted VTEC and measured VTEC over different latitudes to validate improvements in delay over low and mid-latitude (Chakraborty et al, 2014;Tariku, 2016;Natali & Meza, 2017;Tariq et al, 2020). In mid-latitude, IRI models provide fine observations (Kumar et al 2015;Gordiyenko & Yakovets, 2017;Tariku, 2019;Shahzad et al, 2021).…”