Abstract
Abstract. We report here on two cases of poleward-propagating large-scale traveling ionospheric disturbances (LSTIDs) in China during a medium-scale storm between 27 May and 1 June 2011. The observations were conducted by making use of the Global Positioning System network and ionosondes in China and Southeast Asia. One northeastward-propagating LSTID occurred on the morning of 30 May, while the other was observed during the nighttime of 1 June. Both poleward-traveling LSTIDs occurred during the storm's recovery phase in southern China's low-latitude region (geomagnetic latitude ~ 7.3–24° N) and experienced severe dissipation during their propagation from south to north. Although the initial relative amplitude of the nighttime LSTID was ~ 60% larger than that of the morning event, the nighttime event dissipated more quickly than the morning event because of a strong nighttime enhancement in background total electronic content (TEC) during storm time, which led to strong ion-drag dissipation during the evening. The poleward-propagating LSTIDs exhibit a narrower latitudinal range, a smaller amplitude, and a slightly higher elevation compared with the equatorward-moving LSTIDs observed in the same region. Given these features, the poleward-propagating LSTIDs were likely excited by some local source near southern China. Excitation of secondary LSTIDs during the dissipation of some primary medium-scale disturbances from the lower atmosphere is a possible mechanism.
Highlights
Of secondary LSTIDs during the dissipation of some primary magnetically active periods can propagate across the equator medium-scale disturbances from the lower atmosphere is a to the opposite hemisphere and travel poleward
Ding et al.: Observations of poleward-propagating large-scale traveling ionospheric disturbances data provided by CHAMP observations, Bruinsma and Forbes (2009) identified 21 cross-equator LSTIDs during the period 2001–2007, which were excited at high latitudes
Observations obtained with the highfrequency multistatic backscatter sounding radars at Wuhan (30◦ N, 114◦ E) revealed a poleward-propagating LSTID during a geomagnetically quiet time, which was assumed to be a secondary LSTID that originated from the dissipation of medium-scale gravity waves in the lower atmosphere
Summary
We collected TEC data from 241 GPS receivers located around China, whereas 188 were from the Crustal Movement Observation Network of China (CMONOC) and 53 from the International GNSS Service (IGS). The network was completed in late 2010 and offered continuous TEC observations since that time. Using these TEC observations, we constructed twodimensional (2-D) deviation-of-TEC (DTEC) maps to search for LSTIDs over China. We calculated the amplitude of the TEC perturbation in each pixel by taking the average of the TEC variations for all GPS-satellite receiver paths whose ionospheric pierce points crossed the pixel during the time of the observation. We obtained the 2-D TEC variation map for the relevant time frame.
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