Akademik Veri Yönetim Sistemi
GEOMAGNETISM AND AERONOMY, cilt.61, sa.2, ss.277-286, 2021 (SCI-Expanded)
This paper presents a statistical analysis of global ionospheric variation during quiet and disturbed geomagnetic conditions from December 2008 to June 2019. The study comprehends ascending and descending solar periods of the 24th solar cycle. The vertical Total Electron Content (vTEC) data of CODE-GIM are utilized to reveal the TEC variation in the regional and global regions. The disturbance storm time index (Dst) with a storm criterion of diurnal Dst(min) less than -20 nT was used to identify the magnetically quiet/disturbed conditions, and the geomagnetic storms were identified by diurnal Dst(min) less than -50 nT. 36 and 43% of the ascending/descending periods were magnetically disturbed days, respectively. There was no significant change in vTEC variation in the high and middle latitude regions. Still, in the low latitudes, vTECs increased 50 and 25% in the disturbed days of ascending/descending periods, respectively. vTEC values in the low latitudes were found to be 33% higher than the middle latitudes and 100% higher than the high latitudes in quiet days for both periods. vTEC values in the low latitudes were also found to be 50 and 200% higher than the middle and high latitudes in disturbed days, respectively. Also, the Dst and global Total Electron Content (gTEC) variations were compared using the superposed epoch analysis (SEA) for geomagnetic storms. The gTEC values indicate the average vTEC of CODE-GIM grids. The SEA results indicate that the gTEC variation is similar to the Dst pattern of a magnetic storm. The mean gTEC values decreased shortly after when the storm was peaked, corresponding to approximately 20 and 17% in ascending and descending periods, respectively.