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Afraimovich, E. L.
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Afraimovich, E. L.
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- PublicationOpen AccessTesting of the transionospheric radiochannel using data from the global GPS network(2003)
; ; ;Afraimovich, E. L.; Institute of Solar-Terrestrial Physics, Russian Academy of Sciences, Irkutsk, Russia ;Karachenschev, V. A.; Institute of Solar-Terrestrial Physics, Russian Academy of Sciences, Irkutsk, Russia; Using the international ground-based network of two-frequency receivers of the GPS navigation system provides a means of carrying out a global, continuous and fully-computerized monitoring of phase fluctuations of signals from satellite-borne radio engineering systems caused by the Earth's inhomogeneous and nonstationary ionosphere. We found that during major geomagnetic storms, the errors of determination of the range, frequency Doppler shift and angles of arrival of transionospheric radio signals exceeds that for magnetically quiet days by one order of magnitude as a minimum. This can be the cause of performance degradation of current satellite radio engineering navigation, communication and radar systems as well as superlong-baseline radio interferometry systems.137 205 - PublicationOpen AccessGPS detection of the instantaneous response of the global ionosphere to strong magnetic storms with sudden commencement(2002)
; ; ; ; ; ;Afraimovich, E. L.; Institute of Solar-Terrestrial Physics SD, Russian Academy of Sciences, Irkutsk, Russia ;Kosogorov, E. A.; Institute of Solar-Terrestrial Physics SD, Russian Academy of Sciences, Irkutsk, Russia ;Leonovich, L. A.; Institute of Solar-Terrestrial Physics SD, Russian Academy of Sciences, Irkutsk, Russia ;Lesyuta, O. S.; Institute of Solar-Terrestrial Physics SD, Russian Academy of Sciences, Irkutsk, Russia ;Ushakov, I. I.; Institute of Solar-Terrestrial Physics SD, Russian Academy of Sciences, Irkutsk, Russia; ; ; ; Using a new technology for global GPS detection of ionospheric disturbances, GLOBDET, it has been established that a drastic increase in the time derivative of the magnetic field strength during magnetic storms is accompanied by an almost simultaneous decrease in mid-latitude total electron content on the entire dayside. The corresponding correlation coefficient is not below -0.8; the delay with respect to the time of a magnetic storm sudden commencement is about 3-10 min. This is most pronounced for magnetic storms with a well-marked sudden storm commencement. The sudden storm commencements presented in the paper were observed during the initial storm phase. The analysis reported here was made for a set of from 90 to 300 GPS stations for 10 days in 1998-2001 with a different level of geomagnetic activity (Dst from -6 nT to -295 nT, and K p from 0 to 9). The «simultaneous» total electron content response for the events under consideration was 0.1-0.4 TECU, and the travel velocity of the disturbance from the dayside to the nightside was in the order of 10-20 km/s. Results obtained are consistent with earlier ionospheric parameter measurements obtained using high temporal resolution methods.112 200 - PublicationOpen AccessGeomagnetic storms and the occurrence of phase slips in the reception of GPS signals(2002)
; ; ; ; ;Afraimovich, E. L.; Institute of Solar-Terrestrial Physics SD, Russian Academy of Science, Irkutsk, Russia ;Lesyuta, O. S.; Institute of Solar-Terrestrial Physics SD, Russian Academy of Science, Irkutsk, Russia ;Ushakov, I. I.; Institute of Solar-Terrestrial Physics SD, Russian Academy of Science, Irkutsk, Russia ;Voeykov, S. V.; Institute of Solar-Terrestrial Physics SD, Russian Academy of Science, Irkutsk, Russia; ; ; 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.292 511 - PublicationOpen AccessThe response of the ionosphere to faint and bright solar flares as deduced from global GPS network data(2002)
; ; ; ; ;Afraimovich, E. L.; Institute of Solar-Terrestrial Physics SD, Russian Academy of Sciences, Irkutsk, Russia ;Altynsev, A. T.; Institute of Solar-Terrestrial Physics SD, Russian Academy of Sciences, Irkutsk, Russia ;Grechnev, V. V.; Institute of Solar-Terrestrial Physics SD, Russian Academy of Sciences, Irkutsk, Russia ;Leonovich, L. A.; Institute of Solar-Terrestrial Physics SD, Russian Academy of Sciences, Irkutsk, Russia; ; ; Results derived from analysing the ionosphere response to faint and bright solar flares are presented. The analysis used technology of a global detection of ionospheric effects from solar flares as developed by the authors, on the basis of phase measurements of the Total Electron Content (TEC) in the ionosphere using an international GPS network. The essence of the method is that use is made of appropriate filtering and a coherent processing of variations in the TEC which is determined from GPS data, simultaneously for the entire set of visible GPS satellites at all stations used in the analysis. This technique is useful for identifying the ionospheric response to faint solar flares (of X-ray class C) when the variation amplitude of the TEC response to separate line-on-sight to GPS satellite is comparable to the level of background fluctuations. The dependence of the TEC variation response amplitude on the bright flares location on the Sun is investigated170 529