Monitoring global traveling ionospheric disturbances using the worldwide GPS network during the October 2003 storms

Abstract

The global traveling ionospheric disturbances (TIDs) during the drastic magnetic storms of October 29-31, 2003 were analyzed using the Global Position System (GPS) total electron content (TEC) data observed in the Asian-Australian, European and North American sectors. We collected the most comprehensive set of the TEC data from more than 900 GPS stations on the International GNSS Services (IGS) website and introduce here a strategy that combines polynomial fitting and multi-channel maximum entropy spectral analysis to obtain TID parameters. The results of our study are summarized as follows: (1) large-scale TIDs (LSTIDs) and mediumscale TIDs (MSTIDs) were detected in all three sectors after the sudden commencement (SC) of the magnetic storm, and their features showed longitudinal and latitudinal dependences. The duration of TIDs was longer at higher latitudes than at middle latitudes, with a maximum of about 16 h. The TEC variation amplitude of LSTIDs was larger in the North American sector than in the two other sectors. At the lower latitudes, the ionospheric perturbations were more complicated, and their duration and amplitude were relatively longer and larger. (2) The periods and phase speeds of TIDs were different in these three sectors. In Europe, the TIDs propagated southward; in North America and Asia, the TIDs propagated southwestward; in the near-equator region, the disturbances propagated with the azimuth (the angle of the propagation direction of the LSTIDs measured clockwise from due north with 0• ) of 210• showing the influence of Coriolis force; in the Southern Hemisphere, the LSTIDs propagated conjugatedly northwestward. Both the southwestward and northeastward propagating LSTIDs are found in the equator region. These results mean that the Coriolis effect cannot be ignored for the wave propagation of LSTIDs and that the propagation direction is correlated with polar magnetic activity.

Traveling ionospheric disturbances observed at South African midlatitudes during the 29–31 October 2003 geomagnetically disturbed period

“…The geomagnetic storms of 29 and 30 October 2003 belong to some of the most powerful storms studied in the recent years and thus many studies have been conducted to explore the response of the ionosphere to these storms in different latitudes, see for example Horvath and Lovell (2010), Valladares et al (2009, Wang et al (2007). Results presented in this paper will include amplitudes, periods and virtual horizontal velocities of TIDs estimated from TEC measurements from several GPS receivers along similar longitudes in South Africa.…”

Traveling ionospheric disturbances triggered by the 2009 North Korean underground nuclear explosion

“…Furthermore, there are also very long period (3-12 min) disturbances in data from PRN 21 that were reported in Yang et al (2012). However, the periods of the same disturbances were both 2.4 to 5.2 min when employing our method and the frequently used polynomial fitting method (Wang et al, 2007;Tsugawa et al, 2007;Galvan et al, 2011). In essence, our method and the polynomial fitting method obtain the TEC disturbances directly in the time domain, whereas the method of Yang et al (2012) is in the frequency domain.…”

“…As shown in Tables 1 and 2, the periods for high-frequency TIDs are approximately 1 to 2 min and the low-frequency TIDs have periods about 2-5 min. Small differences in detected periods exist between different stations, due to the Doppler effect caused by the relative motion between the GPS satellite and the TIDs (Wang et al, 2007;Garrison et al, 2007). Both the frequencies of high-frequency and low-frequency TIDs are larger than the acoustic cutoff frequency (about 3.3 mHz in the lower atmosphere; Artu et al, 2004), suggesting that the two types of TIDs can be attributed to the acoustic waves.…”

Observation of ionospheric disturbances induced by the 2011 Tohoku tsunami using far-field GPS data in Hawaii

“…To obtain more reliable results, the propagation characteristics for all observed TIDs are estimated (Wang et al 2007;Zhang et al 2013), and the results are listed in Table 1. The basic processes for the estimation method are as follows: 1) extract the Fourier coefficient complex phase differences (time delay in the frequency domain) between the TEC variation series observed at least three stations by Fourier transform; 2) assuming the TIDs are planar waves, the wave numbers in the X-axis (pointing to the east direction) and Y-axis (pointing to the north direction) can be solved according to the coordinates of stations and the phase differences; and 3) estimate the horizontal velocity and azimuth of the TIDs according to the horizontal wave numbers.…”