author = "Klausner, Virginia and Fagundes, Paulo Roberto and Sahai, 
                         Yogeshwar and Wrasse, Cristiano M. and Pillat, Valdir Gil and 
                         Becker-Guedes, F.",
          affiliation = "{Universidade do Vale do Para{\'{\i}}ba (UniVap)} and 
                         {Universidade do Vale do Para{\'{\i}}ba (UniVap)} and {Instituto 
                         Nacional de Pesquisas Espaciais (INPE)} and {Universidade do Vale 
                         do Para{\'{\i}}ba (UniVap)} and {Universidade do Vale do 
                         Para{\'{\i}}ba (UniVap)} and {Universidade do Vale do 
                         Para{\'{\i}}ba (UniVap)}",
                title = "Observations of GW/TID oscillations in the F2 layer at low 
                         latitude during high and low solar activity, geomagnetic quiet and 
                         disturbed periods",
              journal = "Journal of Geophysical Research",
                 year = "2009",
               volume = "114",
               number = "A02313",
                month = "Feb.",
             keywords = "gravity-wave activity, ionosphere, equatorial, events, region, 
                         terminator, Brazil.",
             abstract = "Ionospheric vertical sounding observations, using a digital 
                         ionosonde, are being carried out on a routine basis at Sao Jose 
                         dos Campos (23.2 degrees S, 45.9 degrees W; dip latitude 17.6 
                         degrees S, hereafter referred to as SJC), Brazil, located under 
                         the southern crest of the equatorial ionization anomaly (EIA), 
                         since August 2000. In this paper, we present and discuss the 
                         seasonal variation of gravity wave (GW) and traveling ionospheric 
                         disturbance (TID) oscillations in the ionospheric F2 layer during 
                         high solar activity (HSA, September 2000 to August 2001) and low 
                         solar activity (LSA, January 2006 to December 2006) observed at 
                         SJC during different levels of geomagnetic activity. The GW/TID 
                         signatures in the F2 layer can be seen in the isofrequency lines 
                         of virtual height daily variations for six fixed frequencies (3, 
                         4, 5, 6, 7, and 8 MHz) which show quasiperiodic oscillations 
                         (crests and valleys). The crests and valleys when seen in close 
                         frequencies present a phase difference (i.e., first it is observed 
                         at higher frequency then at lower frequency), indicating a 
                         downward phase velocity. These quasiperiodic oscillations induced 
                         in the virtual heights are divided into three groups as small 
                         amplitude (lower than 40 km), medium amplitude (between 40 km and 
                         60 km), and large amplitude (greater than 60 km). The observations 
                         show that GWs/TIDs are much more pronounced at F layer heights 
                         during HSA than LSA and the large-amplitude GWs/TIDs are present 
                         normally only during HSA.",
                  doi = "10.1029/2008JA013448",
                  url = "http://dx.doi.org/10.1029/2008JA013448",
                 issn = "0148-0227 and 2156-2202",
             language = "en",
           targetfile = "jgra19531.pdf",
        urlaccessdate = "18 jan. 2021"