Abstract
Abstract. Measurements of total electron content (TEC) using 263 GPS receivers located in the North and South America continents are presented to demonstrate the simultaneous existence of traveling ionospheric disturbances (TID) at high, mid, and low latitudes, and in both Northern and Southern Hemispheres. The TID observations pertain to the magnetically disturbed period of 29–30 October 2003 also known as the Halloween storm. The excellent quality of the TEC measurements makes it possible to calculate and remove the diurnal variability of TEC and then estimate the amplitude, wavelength, spectral characteristics of the perturbations, and the approximate velocity of the AGW. On 29 October 2003 between 17:00 and 19:00 UT, there existed a sequence of TEC perturbations (TECP), which were associated with the transit of atmospheric gravity waves (AGW) propagating from both auroral regions toward the geographic equator. A marked difference was found between the northern and southern perturbations. In the Northern Hemisphere, the preferred horizontal wavelength varies between 1500 and 1800 km; the propagation velocity is near 700 m/s and the perturbation amplitude about 1 TEC unit (TECu). South of the geographic equator the wavelength of the TECP is as large as 2700 km, the velocity is about 550 m/s, and the TECP amplitude is 3 TECu. Concurrently with our observations, the Jicamarca digisonde observed virtual height traces that exhibited typical features that are associated with TIDs. Here, it is suggested that differences in the local conductivity between northern and southern auroral ovals create a different Joule heating energy term. The quality of these observations illustrates the merits of GPS receivers to probe the ionosphere and thermosphere.
Highlights
During the last decade, it has become evident that a vast network of GPS receivers is a superb diagnostic of space weather due to its ability to resolve spatial-temporal ambiguities
October 2003 between 17:00 and 19:00 UT, there existed a sequence of total electron content (TEC) perturbations (TECP), which were associated with the transit of atmospheric gravity waves (AGW)
Shiokawa et al (2002) used 1000+ GPS receivers, an all-sky imager, a scanning photometer, and three sounders, all installed in Japan, to study the dynamics, propagation and source of large-scale traveling ionospheric disturbances (TID) (LSTID)
Summary
It has become evident that a vast network of GPS receivers is a superb diagnostic of space weather due to its ability to resolve spatial-temporal ambiguities. The first studies of AWG using GPS receivers employed 150+ globally distributed receivers to indicate the existence of small TEC enhancements developing simultaneously at both north and south auroral regions (Ho et al 1998a, b). The apparent propagation of the TECP bands seems quite similar to the TEC perturbations observed in North America, their amplitude, wavelength, and velocity are very different. A second band of TEC perturbations likely originates almost simultaneously from both high latitude regions between 18:20 and 18:30 UT They are observed to merge near the geographic equator at 19:50 UT. No propagation into the opposite hemisphere is evident during these events
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