[1] In this paper, we plot two-dimensional total electron content (TEC) perturbation maps and investigate the statistical characteristics of large-scale traveling ionospheric disturbances (LSTIDs) during major magnetic storms from 2003 to 2005. The TEC data were obtained from more than 600 GPS receivers in North America within the geographical latitudes of 25°N-55°N. We found a total of 135 cases of LSTIDs, with amplitudes of up to 3.5 TECU and a maximum front width of $4000 km. The mean value of periods, horizontal velocities, and azimuths are 1.8 h, 300 m/s, and 187°(7°west of south), respectively. The mean velocity is obviously slower than that observed at lower latitudes such as Japan. Of all the 135 LSTID events, 35 cases (26%) occurred in the nighttime with their possible source within the region of North America, according to the variation of magnetic H component observed in this region. In addition, the occurrence of LSTIDs peaks at 1200 LT and at 1900 LT. It is also pointed out that the UT dependence of the occurrence of auroral geomagnetic disturbances plays a major role in the forming of UT and LT dependence of the occurrence of LSTIDs observed at midlatitudes.

The article is a review of studies of ionospheric effects carried out in ISTP SB RAS. The main results of GPS/GLONASS radio sounding of ionospheric disturbances of natural and anthropogenic origin are presented. The article is devoted to ionospheric effects of solar eclipses, solar flares, solar terminator, earthquakes, tropical cyclones, large-scale ionospheric disturbances of auroral origin, rocket launches. Dynamics of global electron content analysis is also presented. The special attention is paid on the influence of solar flares and ionospheric irregularities on GPS and GLONASS performance. The work is a tribute to the leader of GNSS-monitoring workgroup Prof.

The paper describes results of studying effects of total electron content (TEC) variations triggered by the Chelyabinsk meteoroid airburst as inferred from unique data of a dense GPS network located around the final part of the meteoroid atmospheric path. Well‐pronounced TEC disturbances with an average period of about 10 min and amplitude of 0.07–0.5 TECU (total electron content unit, 1 TECU = 1016 el m−2) were detected. These disturbances were initiated by an ionospheric source activated about 5–6 min after the airburst. The disturbance velocity damping with time and distance from the airburst was revealed using a GPS interferometric technique. Several modes of TEC disturbances with propagation velocities ranging from 250 to 660 m/s were distinguished through the distance‐time diagram analysis. The estimated position of ionospheric source of TEC disturbances is shifted 36 km southwestward from the airburst, which is most likely to be associated with the conjoint influence of TEC data errors, damping and anisotropy of TID propagation velocity.

We have obtained first experimental evidence in favour of the magnetohydrodynamic (MHD) nature of night‐time medium‐scale travelling ionospheric disturbances (MSTIDs). We used total electron content (TEC) measurement data from the dense GPS networks in California and in Japan for 2008–2009. It was found that the spectral MSTID characteristics are determined by the solar terminator (ST) dynamics. In summer, MSTIDs are detected 1.5–3 hours before the evening ST at 100 km above the point of observations, but at the moment of the evening ST passage through the magnetoconjugate point. At the equinox MSTIDs are registered at once after ST appearance. In winter, MSTIDs are observed 1.5–3 hours after the evening ST occurrence at the point of observations, but at the moment of the evening ST passage in the magnetoconjugate point. The MSTID occurring synchronously with the ST passage through the magnetoconjugate area suggest that the ST‐excited MSTIDs are of MHD nature.

[1] The total electron content (TEC) data obtained by the GPS network and GPS radio interferometry methods developed by the authors has made it possible to determine the spatial structure and dynamics parameters of large-scale traveling ionospheric disturbances (LS TID) generated during the strong magnetic storm on 29 October 2003. It was shown that the LS TID registered in the auroral zone after a sudden storm commencement (SSC) represented a large-scale solitary type wave with an annular front shape whose center was located near the geomagnetic pole. The wave had a period of about 40-60 min and traveled up to 4500 km equatorward. The relative amplitude of the LS TID was 5-10%. Comparison with ionosonde data has shown that this value corresponds to the relative amplitude of electron density disturbance in the F layer maximum of about 45-50%. The velocity and travel direction of the LS TID had a strongly pronounced longitudinal dependence. A ''swirling'' effect was detected in the LS TID movement, the direction of which was opposite to the Earth's rotation. The westward directed zonal projection of LS TID velocity caused this ''swirling'' effect. In the morning and evening sectors the zonal projection exceeded the meridional one. The diurnal movement of the ionization maximum may influence the zonal transfer of LS TID.