Abstract
Abstract. Larger-scale traveling ionospheric disturbances (LSTIDs) were studied using the total electron content (TEC) data observed from global GPS network in the regions of North America, Europe, and East Asia during the magnetic storm of 7~10 November 2004. 4 LSTID events were detected in North America, 4 in Europe, and 3 in East Asia. The parameters of the 11 LSTID events, such as the propagation azimuth (the angle with respect to north, taking clockwise as positive), horizontal phase velocity and damping rate were determined. Our results showed two new propagation features of the LSTIDs. One was the latitudinal dependence of the LSTIDs' propagation azimuths. The LSTIDs tended to deflect more to west from south as they propagated to lower latitudes, which indicated that the Coriolis force was one of the main causes of the LSTIDs' southwestward deviation. The other was the different mean horizontal phase velocities of LSTIDs among different regions. The mean horizontal phase velocity of LSTIDs was 422 ± 36 m s−1 in North America, 381 ± 69 m s−1 in Europe, and 527 ± 21 m s−1 in East Asia, respectively. The results also indicated that the amplitudes of LSTIDs decreased during their propagation for every event, and the daytime damping rates were more than 1 time larger than the nighttime ones due to different ion drag between daytime and nighttime. The source regions of the LSTIDs were likely to be located between geomagnetic latitudes of 68° N and 62° N in North America, and between 65° N and 57° N in Europe, according to the variation of magnetic H component observed in these two regions.
Highlights
Large-scale traveling ionospheric disturbances (LSTIDs) are the response of the ionosphere to atmospheric gravity waves (AGWs), launched by high latitudes sources such as Joule heating, Lorentz forces, or intense particle precipitations (Hunsucker, 1982)
By applying the multichannel maximum-entropy method to the deviations of the total electron content (TEC) series at the global positioning system (GPS) arrays mentioned in Sect. 2.1, we got the variations of the propagation azimuths of the LSTIDs between geomagnetic latitude of 55.3◦ N and 47.7◦ N in North America, and between geomagnetic latitude of 52.6◦ N and 45.3◦ N in Europe, respectively
Mean horizontal phase velocities of LSTIDs observed in Europe (381 ± 69 m s−1) and North America (422 ± 36 m s−1) were obviously slower than those observed in East Asia (527 ± 21 m s−1), which would be mainly caused by latitude differences between these sectors
Summary
Large-scale traveling ionospheric disturbances (LSTIDs) are the response of the ionosphere to atmospheric gravity waves (AGWs), launched by high latitudes sources such as Joule heating, Lorentz forces, or intense particle precipitations (Hunsucker, 1982). Tsugawa et al (2004) statistically studied the LSTIDs in Japan from April 1999 to December 2002 using GPS TEC data from GEONET, they found that the occurrence rate of the disturbed-time LSTIDs was positively correlated with Kp value, and the amplitude damping and growth of the LSTIDs were mainly caused by the upward and downward propagating AGW through ion-drag effect, respectively. Hajkowicz (1990) used the data from ionosonde stations operating throughout the Earth at the time of disturbance to investigate the conjugate effects of LSTIDs in Japan and Australia They found that the storm-induced height rises were only pronounced in the night time sectors. Tsugawa et al (2003) derived the damping rates of LSTIDs between different latitudes in several local time sectors during the geomagnetic storm on 22 September 1999 They indicated that the damping of LSTIDs was mainly caused by the ion-drag effect. Dependence of the LSTIDs’ propagation azimuths and the different mean horizontal phase velocities of LSTIDs among different sectors
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