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Register a new userDegradation of signals and operation failures of radio engineering satellite systems during geospace disturbances accompanied by abrupt changes in the geomagnetic field
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E. L. Afraimovich
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During strong magnetic storms, the errors of determination of the range, frequency Doppler shift and angles of arrival of transionospheric radio signals exceeds the one 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 of superlong-baseline radio interferometry systems. The relative density of phase slips at mid-latitudes exceeds its mean value for magnetically quiet days at least by the order of 1 or 2, that makes a few percent of the total density of GPS observations. Furthermore, the level of phase slips for the GPS satellites located at the sunward side of the Earth was 5-10 times larger compared to the opposite side of the Earth.
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Basic properties of the mid-latitude large-scale traveling ionospheric disturbances (LS TIDs) during the maximum phase of a strong magnetic storm of 6-8 April 2000 are shown. Total electron content (TEC) variations were studied by using data from GPS receivers located in Russia and Central Asia. The nightglow response to this storm at mesopause and termospheric altitudes was also measured by optical instruments FENIX located at the observatory of the Institute of Solar-Terrestrial Physics, (51.9 deg. N, 103.0 deg. E) and MORTI located at the observatory of the Institute of Ionosphere (43.2 deg. N, 77.0 deg. E). Observations of the O (557.7 nm, 630.0 nm, 360-410 nm, and 720-830 nm) emissions originating from atmospheric layers centered at altitudes of 90 km, 97 km, and 250 km were carried out at Irkutsk and of the O_2 (866.5 nm) emission originating from an atmospheric layer centered at altitude of 95 km was carried out at Almaty. Variations of the f_0F2 and virtual altitude of the F2 layer were measured at Almaty as well. An analysis of data was performed for the time interval 17.00-21.00 UT comprising a maximum of the Dst derivative. Results have shown that the storm-induced solitary large-scale wave with duration of 1 hour and with the front width of 5000 km moved equatorward with the velocity of 200 ms-1 to a distance of no less than 1000 km. The TEC disturbance, basically displaying an electron content depression in the maximum of the F2 region, reveals a good correlation with growing nightglow emission, the temporal shift between the TEC and emission variation maxima being different for different altitudes.
In this paper an attempt is made to verify the hypothesis on the role of geomagnetic disturbances as a factor determining the intensity of traveling ionospheric disturbances (TIDs). To improve the statistical validity of the data, we have used the based on the new GLOBDET technology method involving a global spatial averaging of disturbance spectra of the total electron content (TEC). To characterize the TID intensity quantitatively, we suggest that a new global index of the degree of disturbance should be used, which is equal to the mean value of the rms variations in TEC within the selected range of spectral periods (of 20-60 min in the present case). It was found that power spectra of daytime TEC variations in the range of 20-60 min periods under quiet conditions have a power-law form, with the slope index k = -2.5. With an increase of the level of magnetic disturbance, there is an increase in total intensity of TIDs, with a concurrent kink of the spectrum caused by an increase in oscillation intensity in the range of 20-60 min. It was found that an increase in the level of geomagnetic activity is accompanied by an increase in total intensity of TEC; however, it correlates not with the absolute level of Dst, but with the value of the time derivative of Dst (a maximum correlation coefficient reaches -0.94). The delay of the TID response of the order of 2 hours is consistent with the view that TIDs are generated in auroral regions, and propagate equatorward with the velocity of about 300-400 m/s.
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