Akademik Veri Yönetim Sistemi
Harita Dergisi, cilt.86, sa.164, ss.18-28, 2020 (Hakemli Dergi)
A locally planar Total Electron Content (TEC) trend model for the midlatitude region encompassing a major partofTurkeyandsomeBalkancountriesisinvestigated by estimating its coefficients in the least square sense for the solar minimum year 2009 and the solarmaximumyear2014.TheTECvaluesareobtained from Global Ionospheric Maps (GIM) which have a spatial resolution of 2.5° in latitude and 5° in longitude. The temporal resolution of the maps is two hours. The coefficients, as well as their 7-day and 27-day medians are investigated which in turn reveal the diurnal, seasonal and semiannual periodicities in the midlatitude ionosphere TEC trend. The estimated model coefficients are used to generate model maps and the difference between these and actual GIM are obtained in squared 𝐿ଶ sense as a performance indicator. Despite the major distinctness in solar activity levels in both years, the differences for both 2009 and 2014 generally remain below 0.1% and the deviation of the model from actual GIM never exceeds 0.9% even on days with severe geomagnetic disturbances. The planar trend model provides a successful representation of TEC for the midlatitude region taken into consideration in both years. Periods with higher levels of solar activity result in estimated model coefficients with both increased values and spread.