Estimation of the daily mean ionospheric total electron content using global ionospheric maps

The seasonal, diurnal, latitudinal and longitudinal variations of ionospheric total electron content (TEC) is investigated using global ionospheric maps (GIM) corresponding to a twenty-four month period (1999-2000) at Ankara (39.88°N, 32.35°E), Turkey. The dependence of those TEC values on solar zenith angle and season is also examined. It is observed that the daily mean TEC values for one month are sufficient to extrapolate the corresponding values both for the previous and the following months. This is illustrated on interpolation for a whole twenty-four month period using only the daily mean values corresponding to February, May, August and November. It is interesting to note that the variations of solar and geomagnetic indices are reflected on the daily mean TEC values with a delay about 1 to 3 days and 1 to 2 days, respectively. It is also interesting to note that for the year 2000, winter anomaly was not concentrated in high midlatitudes as usually expected.