Observations of TIDs over South and Central America

Abstract

TEC values measured by GPS receivers that belong to the low‐latitude ionosphere sensor network (LISN) and several other networks that operate in South and Central America were used to study the characteristics and origin of traveling ionospheric disturbances (TID) in these regions. The TEC perturbations associated with these TIDs show a high degree of spatial coherence over distances > 1000 km allowing us to use measurements from receivers spaced by hundreds of km to calculate the TIDs' travel velocities, propagation direction, and scale size. We first applied the TID analysis to TEC measurements corresponding to 4 July 2011. This processing method is then used to study the characteristics of TIDs for 20 and 21 August 2011, a period when a tropical storm was active in the Caribbean region. A pronounced increase in TID activity was observed in South and Central America at 16 UT on 20 August 2011 lasting until the end of 21 August 2011. The TID velocities show a very variable pattern that depends upon their local time and location. Counter‐streaming TIDs were observed over the western part of South America on 21 August 2011. Regional maps of tropospheric temperature brightness, measured by the GOES‐12 satellite, are used to identify and follow the development of the tropical storm (TS) Irene and several deep convective plumes. TIDs were observed propagating away from TS Irene. This storm moved into the Caribbean region and intensified earlier on 20 August spawning a train of atmospheric gravity waves (AGW). The small scale size, the velocity less than 150 m/s, and the close location of several TIDs with respect to TS Irene indicate that these TIDs may be the result of primary AGWs that reached the F‐region bottomside. These results open the possibility of using TEC values measured by networks of GPS receivers to construct regional, and probably global, maps of TIDs, identify their origin, and study in detail the characteristics of TIDs corresponding to primary and secondary AGWs.