Comparison of the TEC-based ionospheric disturbance indices AATR and WTEC

Abstract

Various ionospheric indices based on Global Navigation Satellite Systems data are widely used to study ionospheric disturbances. Two of them, produced from the Slant Total Electron Content measurements are studied in the paper: well known AATR index and relatively new WTEC index. A comparative statistical analysis of AATR and WTEC indices was made using ISTP SB RAS receivers network. We compared AATR and WTEC indices for studying small- and mid-scale ionospheric disturbances in different geophysical conditions and different geographical regions. The analysis was carried out at high, equatorial and middle latitudes during 2014–2017. It is shown that the contribution of diurnal variations of the background ionosphere to AATR is higher than to WTEC. It is shown that at high latitudes the WTEC and AATR dynamics correlates with the level of geomagnetic disturbance (Kp index). At mid-latitudes, the contribution of Vertical Total Electron Content prevails other effects. Preliminary statistical analysis of 25 earthquakes with magnitude >6.8 shown that effect of internal atmospheric waves prevails the effect of shock acoustic waves from ground vibrations. The analysis demonstrated that at low disturbance levels (WTEC < 0.1TECU) WTEC index looks more sensitive than AATR; at high disturbance levels, the AATR is nearly proportional to WTEC with a factor of 1.5min−1.