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%0 Conference Proceedings
%4 sid.inpe.br/mtc-m21b/2015/03.05.19.29
%2 sid.inpe.br/mtc-m21b/2015/03.05.19.29.40
%T F region height behavior over Cachoeira Paulista, Brazil, using digisonde data
%D 1994
%A Medeiros, Rui Tertuliano,
%A Batista, Inez Staciarini,
%A Paula, Eurico Rodrigues de,
%A Abdu, Mangalathayil Ali,
%@affiliation Instituto Nacional de Pesquisas Espaciais (INPE)
%@affiliation Instituto Nacional de Pesquisas Espaciais (INPE)
%@affiliation Instituto Nacional de Pesquisas Espaciais (INPE)
%@affiliation Instituto Nacional de Pesquisas Espaciais (INPE)
%@electronicmailaddress
%@electronicmailaddress inez.batista@inpe.br
%@electronicmailaddress eurico@dae.inpe.br
%@electronicmailaddress maabdu@dae.inpe.br
%E Sakanaka, P. H.,
%E Del Bosco, Edson,
%E Alves, Maria Virginia,
%B International Conference on Plasma Physics.
%C Foz do Iguaçu, PR
%8 31 Oct. - 04 Nov.
%S Proceedings
%X 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.
%@language en
%3 Medeiros_f region.pdf


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