@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"
}