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Ann. Geophys., 25, 863-873, 2007
www.ann-geophys.net/25/863/2007/
© European Geosciences Union 2007
The ionospheric response in the Brazilian sector during the super geomagnetic storm on 20 November 2003
F. Becker-Guedes1, Y. Sahai1, P. R. Fagundes1, E. S. Espinoza2, V. G. Pillat1, W. L. C. Lima3, Su. Basu4, Sa. Basu5, Y. Otsuka6, K. Shiokawa6, E. M. MacKenzie7, X. Pi8, and J. A. Bittencourt9
1Universidade do Vale do Paraiba (UNIVAP), São José dos Campos, SP, Brazil
2Radio Observatorio de Jicamarca, Instituto Geofisico del Peru, Lima, Peru
3Centro Univ. Luterano de Palmas (CEULP), Universidade Luterana do Brasil (ULBRA), Palmas, TO, Brazil
4Center for Space Physics, Boston University, Boston, MA, USA
5Space Vehicles Directorate, Air Force Research Laboratory, Hanscom AF Base, MA, USA
6STELAB, Nagoya University, Toyokawa, Japan
7Institute for Scientific Research, Boston College, Chestnut Hill, MA, USA
8Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA, USA
9Instituto Nacional de Pesquisas Espaciais (INPE), São José dos Campos, SP, Brazil
Abstract. A very intense geomagnetic storm (superstorm) began with storm sudden
commencement (SSC) at 08:03 UT on 20 November 2003, as a result of the
coronal mass ejection (CME) by sunspot 484 hurled into space on 18 November
2003. The geomagnetic storm attained |Dst|max=472 nT at
20:00 UT (20 November). In this paper we present the simultaneous ionospheric
sounding observations, using the Canadian Advanced Digital Ionosondes
(CADIs), carried out from Palmas (PAL; 10.2° S, 48.2° W; dip
latitude 5.5° S; a near equatorial station) and São José dos
Campos (SJC; 23.2° S, 45.9° W; dip latitude 17.6° S; station
located under the crest of equatorial ionospheric anomaly), Brazil. In
addition, total electron content (TEC) measurements from several GPS
receiving stations in the Brazilian sector during this storm are presented.
The simultaneous ionospheric sounding observations carried out at SJC and
PAL, and TEC observations on 3 consecutive days viz., 19 November (quiet),
20 November (disturbed) and 21 November (recovery phase) are presented.
Salient features from the ionospheric observations in the Brazilian sector
during the superstorm are discussed. The difference in the observed
ionospheric response at the two stations (PAL and SJC) is considerable. This
is not surprising given that PAL is close to the magnetic equator and SJC is
near the crest of the equatorial ionospheric anomaly (EIA). It should be
pointed out that soon after the SSC (about 4 h later), the F-region
critical frequency (foF2), the F-region peak height (hpF2), and variations
of virtual heights at different frequencies (iso-frequency plots) all show
wavelike oscillations of the F-region during daytime at both the ionospheric
sounding stations. Unusual rapid uplifting of F-region at PAL was observed
during both the main and recovery phases of the storm.
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