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@InProceedings{MedeirosBatiPaulAbdu:1994:ReHeBe,
               author = "Medeiros, Rui Tertuliano and Batista, Inez Staciarini and Paula, 
                         Eurico Rodrigues de and Abdu, Mangalathayil Ali",
          affiliation = "{Instituto Nacional de Pesquisas Espaciais (INPE)} and {Instituto 
                         Nacional de Pesquisas Espaciais (INPE)} and {Instituto Nacional de 
                         Pesquisas Espaciais (INPE)} and {Instituto Nacional de Pesquisas 
                         Espaciais (INPE)}",
                title = "F region height behavior over Cachoeira Paulista, Brazil, using 
                         digisonde data",
            booktitle = "Proceedings...",
                 year = "1994",
               editor = "Sakanaka, P. H. and Del Bosco, Edson and Alves, Maria Virginia",
         organization = "International Conference on Plasma Physics.",
             abstract = "In March 1990 a Digisonde has been installed in Cachoeira Paulista 
                         (22.5ºS, 45ºW), a low latitude station over Brazil. The data from 
                         April 1990 to january 1993 has been analyzed in order to study the 
                         virtual (h'F) and the true (hmF) heights of the F region Both h'F 
                         and hmF show a consistent pre-dawn maximum ocurring around 0800 UT 
                         (0500 LT) that is more pronounced from April to August. From 
                         setptember to december we observer two pre-dawn maxima occurring 
                         between 0000 UT and 0800 UT. The earlier maximum becomes more 
                         important during the local summer months. In spite of this very 
                         general characteristics we have observed a peculiar behavior 
                         during disturbed periods. On April 29 and 30, 1990, two disturbed 
                         days with EKp equal to 32º and 24+ respectively, the F layer 
                         height showed a much more pronounced maxima around 0800 UT. The 
                         maximum in hmF (corresponding to the frequency of 5 MHz) that was 
                         around 300 km during the quiet days, increased to 370 and 395 km 
                         on the disturbed days. Another peculiar behavior was observed 
                         during the development of the main phase of the magnetic storm on 
                         June 12, 1990 when the hmF increased to 350 km around 2230 UT (the 
                         mean value is around 230 km during winter months). In both of 
                         these cases, spread F was observed over Cachoeira Paulista 
                         simultaneously with the uplift of the layer. Is is well known that 
                         spread F over low latitude stations such as Cachoeira Paulista is 
                         generally correlated with the development of plasma bubbles that 
                         are generated over equatorial stations and extend to the low 
                         latitudes through the magnetic field lines. However, in April 1990 
                         case, spread F was not observed over Fortaleza (4ºS, 38ºW), an 
                         station located near the magnetic equator and at the same 
                         longitude sector, but eastward of Cachoeira Paulista. In the June 
                         1990 spread F was observed over Fortaleza (FZ) but nearly 
                         simultaneously with the event over Cachoeira Paulista (CP). The 
                         effects of electric fields and thermospheric winds in the 
                         generation of the disturbed behavior of the F region height are 
                         discussed.",
  conference-location = "Foz do Igua{\c{c}}u, PR",
      conference-year = "31 Oct. - 04 Nov.",
             language = "en",
           targetfile = "Medeiros_f region.pdf",
        urlaccessdate = "2025, Feb. 09"
}


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