Geomagnetic storms and the occurrence of phase slips in the reception of GPS signals

We have investigated a dependence of the relative density of GPS phase slips on the geomagnetic disturbance level. The study is based on using Internet-available selected data from the global GPS network, with the simultaneously handled number of receiving stations ranging from 160 to 323. The analysis used four days from the period 1999-2000, with the values of the geomagnetic field disturbance index Dst from 5 to – 300 nT. During strong magnetic storms, the relative density of phase slips on mid-latitudes exceeds that for magnetically quiet days by one-two orders of magnitude as a minimum, and reaches a few percent of the total density of observations. Furthermore, the level of phase slips for the GPS satellites located on the sunward side of the Earth was by a factor of 5-10 larger compared with the opposite side of the Earth. The level of slips of L 1 phase measurements at the fundamental GPS frequency is at least one order of magnitude lower than that in L 1 – L 2 measurements. The slips of L 1 – L 2 measurements are most likely to be caused by the high level of slips of L 2 phase measurements at the auxiliary frequency. As an alternative, we developed and tested a new method for determining TEC variations using only data on the pseudo-range and phase measurements at fundamental frequency L 1 . The standard deviation of the TEC variations which were obtained in phase measurements at two frequencies, L 1 – L 2 , and at fundamental frequency L 1 , does not exceed 0.1 TECU, which permits this method to be used in strong disturbance conditions when phase slips at auxiliary frequency L 2 are observed

The MHD nature of ionospheric wave packets excited by the solar terminator

We obtained the first experimental evidence for the magnetohydrodynamic (MHD) nature of ionospheric medium-scale travelling wave packets (MSTWP). We used data on total electron content (TEC) measurements obtained at the dense Japanese network GPS/GEONET (1220 stations) in 2008-2009. We found that the diurnal, seasonal and spectral MSTWP characteristics are specified by the solar terminator (ST) dynamics. MSTWPs are the chains of narrow-band TEC oscillations with single packet's duration of about 1-2 hours and oscillation periods of 10-20 minutes. Their total duration is about 4--6 hours. The MSTWP spatial structure is characterized by a high degree of anisotropy and coherence at the distance of more than 10 wavelengths. The MSTWP direction of travelling is characterized by a high directivity regardless of seasons. Occurrence rate of daytime MSTWPs is high in winter and during equinoxes. Occurrence rate of nighttime MSTIDs has its peak in summer. These features are consistent with previous MS travelling ionosphere disturbance (TID) statistics obtained from 630-nm airglow imaging observations in Japan. In winter, MSTWPs in the northern hemisphere are observed 3-4 hours after the morning ST passage. In summer, MSTWPs are detected 1.5-2 hours before the evening ST occurrence at the point of observations, at the moment of the evening ST passage in the magneto-conjugate point. Both the high Q-factor of oscillatory system and synchronization of MSTWP occurrence with the solar terminator passage at the point of observations and in the magneto-conjugate area testify the MHD nature of ST-excited MSTWP generation. The obtained results are the first experimental evidence for the hypothesis of the ST-generated ion sound waves.Comment: 12 pages, 3 figure

Geomagnetic storms and the occurrence of phase slips in the reception of GPS signals

We have investigated a dependence of the relative density of GPS phase slips on the geomagnetic disturbance level. The study is based on using Internet-available selected data from the global GPS network, with the simultaneously handled number of receiving stations ranging from 160 to 323. The analysis used four days from the period 1999-2000, with the values of the geomagnetic field disturbance index Dst from 5 to – 300 nT. During strong magnetic storms, the relative density of phase slips on mid-latitudes exceeds that for magnetically quiet days by one-two orders of magnitude as a minimum, and reaches a few percent of the total density of observations. Furthermore, the level of phase slips for the GPS satellites located on the sunward side of the Earth was by a factor of 5-10 larger compared with the opposite side of the Earth. The level of slips of L 1 phase measurements at the fundamental GPS frequency is at least one order of magnitude lower than that in L 1 – L 2 measurements. The slips of L 1 – L 2 measurements are most likely to be caused by the high level of slips of L 2 phase measurements at the auxiliary frequency. As an alternative, we developed and tested a new method for determining TEC variations using only data on the pseudo-range and phase measurements at fundamental frequency L 1 . The standard deviation of the TEC variations which were obtained in phase measurements at two frequencies, L 1 – L 2 , and at fundamental frequency L 1 , does not exceed 0.1 TECU, which permits this method to be used in strong disturbance conditions when phase slips at auxiliary frequency L 2 are observed.PublishedJCR Journalope

The first GPS-TEC imaging of the space structure of MS wave packets excited by the solar terminator

Using TEC measurements from the dense network of GPS sites GEONET, we have obtained the first GPS-TEC image of the space structure of medium-scale traveling wave packets (MS TWP) excited by the morning solar terminator (ST). We found that ST-generated wave packets have duration of about 1–2 h and time shift of about 1.5–6 h after the morning ST appearance at an altitude of 300 km. The TWP wave front extends along the morning ST line with the angular shift of about 20°. The time period and wave-length of ST-generated wave packets are about 10–20 min and 200–300 km, respectively. The velocity of the TWP phase front traveling is of about 300 m/s. The space image of MS TWP manifests itself in pronounced anisotropy and high coherence over a long distance of about 2000 km

A review of GPS/GLONASS studies of the ionospheric response to natural and anthropogenic processes and phenomena

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. E.L. Afraimovich (12 March 1940–8 November 2009)

A review of GPS/GLONASS studies of the ionospheric response to natural and anthropogenic processes and phenomena

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. E.L. Afraimovich (12 March 1940–8 November 2009)