ИСТИНА

The aim of the present work is to compare the global ionospheric maps, GIM, of vertical TEC (VTEC) with the results of low- and high-orbital radio tomographic ionospheric imaging (LORT and HORT, respectively) and with the data of UV spectral imaging, which are, to a first approximation, proportional to the integral of squared electron density. The data from LORT systems in Russia (Moscow-Svalbard) and Alaska (Arctic Village-Cordova) have been inverted for the distributions of electron density, which were then used to calculate VTEC. We compare the global VTEC maps with the results of LORT, HORT and the data of UV spectrometry using the GUVI instrument (Global Ultraviolet Imager). The comparisons cover the time interval from 2003 to 2008, which includes both geomagnetically quiet periods and storms. We also demonstrate the possibilities of GNSS TEC studies in connection with solar flares and artificial ionospheric heating.