Geomagnetic control of the spectrum of traveling ionospheric disturbances based on data from a global GPS network

Abstract

Abstract.In this paper an attempt is made to verify the hypothesis of the role of geomagnetic disturbances as a factor in determining the intensity of traveling ionospheric disturbances (TIDs). To improve the statistical validity of the data, we have used the 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). The analysis has been made for a set of 100 to 300 GPS stations for 10 days with a different level of geomagnetic activity (Dst from 0 to −350 nT; the Kp index from 3 to 9).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 in the level of magnetic disturbance, there is an increase in the 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. The TEC variation amplitude is found to be smaller at night than during the daytime, and the spectrum decreases in slope, which is indicative of a disproportionate increase in the amplitude of the small-scale part of the spectrum.It was found that an increase in the level of geomagnetic activity is accompanied by an increase in the total intensity of TEC; however, it does not correlate with the absolute level of Dst, but rather 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.Correspondence to: E. L. Afraimovich (afra@iszf.irk.ru)

Degradation of GPS performance in geomagnetically disturbed conditions

“…These results are in reasonably good agreement with data reported by Afraimovich et al ( , 2001bAfraimovich et al ( , 2001cAfraimovich et al ( , 2002aAfraimovich et al ( , 2002b. Phase measurements are more sensitive to equipment failures and to various interference affecting the GPS ''satellite-receiver'' channel when compared with group delay measurements that are directly used for navigation purposes.…”

“…The high positive correlation between the growth of the density of phase slips and the intensity of ionospheric irregularities during geomagnetic disturbances as detected by Afraimovich et al ( , 2001aAfraimovich et al ( , 2001bAfraimovich et al ( , 2002aAfraimovich et al ( , 2002b, points to the fact that the increase in slips is caused by the scattering of the GPS signal from ionospheric irregularities. Afraimovich et al (2001c) found that the growth of The same as in Fig. 9, but for the magnetically disturbed day of July 15, 2000 (day 197) Fig.…”

“…It is evident from Table 1 that most of the stations under consideration are located within 50-58°of geomagnetic latitude. In magnetic storm conditions the auroral oval can reach these latitudes; for that reason, in this region the ionosphere should be regarded not as the mid-latitude ionosphere but as the auroral ionosphere, characterized by fast, profound fluctuations of the trans-ionospheric signal amplitude and phase (Afraimovich et al 2001c, Coster et al 2001). Using the geomagnetic storm of 15 July 2000 as an example, Afraimovich et al (2001a) investigated the dependence of GPS performance on the night side at midlatitudes on the level of geomagnetic disturbance.…”

An investigation of ionospheric disturbances over the north-eastern region of Russia in October 2003 using auroral images and data from a network of ground-based instruments

“…4N, 88.1E), and the monitoring system of ionosphere disturbances according to the GPS signals receivers data (Afraimovich et al, 2001). Irkutsk ISR is located in 98 km to the north-west of Irkutsk.…”

Penetration of internal gravity waveguide modes into the upper atmosphere

“…Notice that waveguide modes have been studied before [Francis, 1973a, b], and the results are being widely used for theoretical works and for interpreting observation of various disturbances, including those in the upper atmosphere [Shibata, Okuzawa, 1983;Afraimovich et al, 2001;Vadas, Liu, 2009;Vadas, Nicolls, 2012;Idrus et al, 2013;Heale et al, 2014;Hedlin, Drob, 2014 et al]. Francis [Francis, 1973a, b] defined dispersion characteristics and vertical structures of waveguide modes.…”