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Ann. Geophys., 22, 3231-3239, 2004
www.ann-geophys.net/22/3231/2004/
© European Geosciences Union 2004
Geomagnetic storm and equatorial spread-F
F. Becker-Guedes1, Y. Sahai1, P. R. Fagundes1, W. L. C. Lima2, V. G. Pillat1, J. R. Abalde1, and J. A. Bittencourt3
1Universidade do Vale do Paraiba (UNIVAP), 12244-000 Sao Jose dos Campos, SP, Brazil
2Centro Universitario Luterano de Palmas (CEULP), Universidade Luterana do Brasil (ULBRA), 77054-970 Palmas, TO, Brazil
3Instituto Nacional de Pesquisas Espacias (INPE), 12201-970 Sao Jose dos Campos, SP, Brazil
Abstract. In August 2000, a new ionospheric sounding station was established at Sao
Jose dos Campos (23.2° S, 45.9° W; dip latitude 17.6° S),
Brazil, by the University of Vale do Paraiba (UNIVAP). Another ionospheric
sounding station was established at Palmas (10.2° S, 48.2° W; dip
latitude 5.5° S), Brazil, in April 2002, by UNIVAP in collaboration with
the Lutheran University Center of Palmas (CEULP), Lutheran University of
Brazil (ULBRA). Both the stations are equipped with digital ionosonde of the
type known as Canadian Advanced Digital Ionosonde (CADI). In order to study
the effects of geomagnetic storms on equatorial spread-F, we present and
discuss three case studies, two from the ionospheric sounding observations
at Sao Jose dos Campos (September and November 2000) and one from the
simultaneous ionospheric sounding observations at Sao Jose dos Campos and
Palmas (July 2003). Salient features from these ionospheric observations are
presented and discussed in this paper. It has been observed that sometimes
(e.g. 4-5 November 2000) the geomagnetic storm acts as an inhibitor (high
strong spread-F season), whereas at other times (e.g. 11-12 July 2003) they act
as an initiator (low strong spread-F season), possibly due to corresponding
changes in the quiet and disturbed drift patterns during different seasons.
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