Sergey V. Voeykov

Parameters of large‐scale TEC disturbances during the strong magnetic storm on 29 October 2003

[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.

Ionospheric effects of the March 29, 2006, solar eclipse over Kazakhstan

The results of studying the ionospheric effects of the March 29, 2006, solar eclipse are presented. The results were obtained in measurements of local electron density (ED) at Alma-Ata vertical ionospheric sounding station and total electron content (TEC) at the Central Asia network of two-frequency receivers of the GPS navigation system. The ED decrease at the F-layer maximum reached approximately 28%, the delay of the minimum value of EC relative to the moment of the eclipse maximum phase was about 11 min, the relaxation time was 4 min, and the duration of the EC depression at the 0.5 level was 45 min. Dynamic interlayer formations were observed in the ionosphere near the eclipse maximum phase. A traveling ionospheric disturbance, probably generated at the shock wave front during the supersonic motion of the Moon’s shadow, was detected. The disturbance period and the horizontal projection of the velocity were about 90 min and ∼680 m/s, respectively. The wave vector azimuth (145°) coincides with the model value of the normal to the shock front.

Variations in the Total Electron Content during the Powerful Typhoon of August 5-11, 2006, near the Southeastern Coast of China

The variations in the total electron content (TEC), obtained from the data of 11 ground-based GPS stations in the region (5°S–80°N; 110–160°E) in the period August 2–15, 2006, have been analyzed in order to search for possible ionospheric manifestations of the SAOMAI powerful typhoon (August 5–11, 2006) near the south-eastern coast of China. The global TEC maps (GIM) have also been used. In the region of the typhoon action during the magnetic storm of August 7, 2006, an intensification of the TEC variations in the evening local time within the 32–128 min periods range was detected. However, this effect was most probably caused by the dynamics of the irregular structure of the equatorial anomaly and by the disturbed geomagnetic situation (Kp ∼ 3–6, Dst varied from −74 to −153 nT). The analysis of the diurnal variations in the absolute values of TEC and TEC variations with periods of 2–25 min did not reveal a substantial increase in the intensity and changes in the spectrum of the TEC variations in the period of typhoon action as compared to the adjacent days. Thus, we failed to detect ionospheric disturbances unambiguously related to the SAOMAI typhoon.

Large-scale disturbances of auroral origin during strong magnetic storms of October 29–31, 2003, and November 7–11, 2004, according to the data of the GPS network and ionosondes

The intensity of large-scale traveling ionospheric disturbances (LS TIDs), registered according to measurements of the total electron content (TEC) during the magnetic storms of October 29–31, 2003, and November 7–11, 2004, has been compared with that of local electron density disturbances. The data of TEC measurements at ground-based GPS receivers located near the ionospheric stations and the corresponding values of the critical frequency of the ionospheric F region (foF2) were used for this purpose. The variations in TEC and foF2 were similar for all events mentioned above. The previous assumption that the region of thickness 150–200 km in the vicinity of the ionospheric F region mainly contributes to TEC modulation was confirmed for the cases when the electron density disturbance at an F region maximum was not more than 50%. However, this region probably becomes more extensive in vertical when the electron density disturbance in the vicinity of the ionospheric F region is about 85%.

Use of the index of TEC vertical variation disturbance in studying ionospheric effects of the Chelyabinsk meteorite

The results of an analysis of the ionospheric effects accompanying fall of the Chelyabinsk meteorite on February 15, 2013 are presented using a method of calculating the index of the disturbance of total electron content vertical variations (Wtec) according to data from the GPS receiver network. A substantial increase (by a factor of 2–3) in the Wtec index with a duration of ~1.5 h was observed in the studied region after the main height explosion accompanying the meteorite fall at 0320 UT. The ionospheric response in Wtec was most significant statistically registered at the radio rays “receiver–satellite” for the GPS located southward from the place of explosion.

MHD nature of ionospheric wave packets generated by the solar terminator

The morphology of medium-scale traveling wave packets is for the first time presented based on the total electron content (TEC), measured at the global network of GPS receivers (up to 1500 stations) during the long period (from 1998 to 2007) and at the GPS/GEONET dense Japan network (1220 stations) in 2008—2009. In the time domain, these packets are chains of narrowband TEC variations (trains) with a duration of about 1—2 h, a total duration of up to 6 h, and a variation period of 10—30 min. In the winter Northern Hemisphere, traveling wave packets are observed mostly 3 h after the passage of the morning solar terminator. In the equinox they appear after the passage of the solar terminator without a pronounced delay or advance. In summer traveling wave packets are registered 1.5—2 h before the appearance of the evening solar terminator at the observation point when the solar terminator passes in the magnetically conjugate region. The spatial structure of traveling wave packets is characterized by a high degree of anisotropy and coherence at a distance larger than ten wavelengths (the wavelength is 100—300 km). A high quality of the oscillatory system and synchronization with the appearance of the solar terminator at the observation point and in the magnetically conjugate region indicate that the generation of traveling wave packets by the solar terminator is of the MHD nature. Our results for the first time experimentally confirm the hypothesis that the solar terminator generates ion sound waves, proposed by Huba et al. [2000b].

Ionosphere and magnetosphere disturbance impact on operation slips of Global navigation satellite systems at mid- and high-latitudes

We studied the dynamics of the GLONASS and GPS radio physical signal slips, as well as the slips in determining the total electron content (TEC) at the stations in the mid- and high-latitude regions under different geophysical conditions over 2014 Nov - 2015 Jul. At high latitudes, the pseudo-range P1 measurement slip density is shown to be lower for the GLONASS system, than that for GPS. At mid-latitudes, the TEC slip mean density (N1 TECU/min) under quiet geomagnetic conditions practically does not depend on the Kp and AE index behavior, and does not exceed 12%. At high-latitudes, N1 TECU/min in winter is generally higher, than that in the summer, and may reach 50-60%. The N1 TECU/minvariation at highlatitudes correlates with the geomagnetic index behaviors; however, it depends on Kp and AE essentially differently. Under disturbed conditions, N1 TECU/min increases as AE grows more slowly, that it does under quiet conditions. On the contrary, N1 TECU/min growth as Kp increases under disturbed conditions occurs on a factor of 1,5 faster, than it does under quiet geomagnetic conditions. The N1TECU/min value dependences on the ionospheric disturbance index (Wtec) at mid- and high-latitudes are similar. An increase in the TEC slip density, N1TECU/min in wintertime occurs on a factor of 1,5 faster, than it does in summer. Simultaneously, at high-latitudes, the N1TECU/min growth with the Wtec increase occurs on a factor of 2-2,5 faster, than it does at the mid-latitudes.