  A comparative statistical analysis of AATR and WTEC indices was conducted
based on data from the ISTP SB RAS GNSS receivers network. It is shown that at
high levels of ionospheric disturbance (for WTEC > 0.1 TECU), the AATR index is
proportional to the WTEC index with a factor of $1.5min^{-1}$. At small levels
of ionospheric disturbance (for WTEC < 0.1 TECU), this proportionality is
violated. It is shown that the contribution of daily dynamics of the background
ionosphere to the AATR index is higher than to the WTEC index. This leads to a
higher sensitivity of the WTEC index to disturbances. This also leads to
violating the proportionality between WTEC and AATR indices at low levels of
ionospheric disturbance. It is shown that at high latitudes the dynamics of the
WTEC and AATR indices correlate significantly with the level of geomagnetic
disturbance Kp. At mid-latitudes, the contribution of solar radiation
variations (F10.7 index) and vertical seismic variations exceeds the influence
of Kp variations. The program for calculating WTEC indices, used in the paper
is put into open access.
