Abstract
The present study investigates the ionospheric Total Electron Content (TEC) variations in the
lower mid-latitude Turkish region from the Turkish permanent GNSS network (TPGN) and
International GNSS Services (IGS) observations during the year 2016. The corresponding vertical
TEC (VTEC) predicted by Auto Regressive Moving Average (ARMA) and International Reference
Ionosphere 2016 (IRI-2016) models are evaluated to realize their effectiveness over the region.
The spatial, diurnal and seasonal behavior of VTEC and the relative VTEC variations are modeled
with Ordinary Least Square Estimator (OLSE). The spatial behavior of modeled result during
March equinox and June solstice indicates an inverse relationship of VTEC with the longitude
across the region. On the other hand, the VTEC variation during September equinox and
December solstice including March equinox and June solstice are decreasing with increase in
latitude. The GNSS observed and modeled diurnal variation of the VTEC show that the VTEC
slowly increases with dawn, attains a broader duration of peak around 09.00 to 12.00 UT, and
thereafter decreases gradually reaching minimum around 21.00 UT...