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Annales Geophysicae An interactive open-access journal of the European Geosciences Union
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Volume 21, issue 12
Ann. Geophys., 21, 2315–2322, 2003
https://doi.org/10.5194/angeo-21-2315-2003
© Author(s) 2003. This work is distributed under
the Creative Commons Attribution 3.0 License.
Ann. Geophys., 21, 2315–2322, 2003
https://doi.org/10.5194/angeo-21-2315-2003
© Author(s) 2003. This work is distributed under
the Creative Commons Attribution 3.0 License.

  31 Dec 2003

31 Dec 2003

Equatorial F-region plasma depletion drifts: latitudinal and seasonal variations

A. A. Pimenta1, P. R. Fagundes2, Y. Sahai2, J. A. Bittencourt1, and J. R. Abalde2 A. A. Pimenta et al.
  • 1Instituto Nacional de Pesquisas Espaciais − INPE − C.P. 515, 12201-970, São José dos campos, SP, Brazil
  • 2Universidade do Vale do Paraba − UNIVAP, Av. Shishima Hifumi 2911, São José dos Campos, SP, Brazil

Abstract. The equatorial ionospheric irregularities have been observed in the past few years by different techniques (e.g. ground-based radar, digisonde, GPS, optical instruments, in situ satellite and rocket instrumentation), and its time evolution and propagation characteristics can be used to study important aspects of ionospheric dynamics and thermosphere-ionosphere coupling. At present, one of the most powerful optical techniques to study the large-scale ionospheric irregularities is the all-sky imaging photometer system, which normally measures the strong F-region nightglow 630 nm emission from atomic oxygen. The monochromatic OI 630 nm emission images usually show quasi-north-south magnetic field-aligned intensity depletion bands, which are the bottomside optical signatures of large-scale F-region plasma irregularities (also called plasma bubbles). The zonal drift velocities of the plasma bubbles can be inferred from the space-time displacement of the dark structures (low intensity regions) seen on the images. In this study, images obtained with an all-sky imaging photometer, using the OI 630 nm nightglow emission, from Cachoeira Paulista (22.7° S, 45° W, 15.8° S dip latitude), Brazil, have been used to determine the nocturnal monthly and latitudinal variation characteristics of the zonal plasma bubble drift velocities in the low latitude (16.7° S to 28.7° S) region. The east and west walls of the plasma bubble show a different evolution with time. The method used here is based on the western wall of the bubble, which presents a more stable behavior. Also, the observed zonal plasma bubble drift velocities are compared with the thermospheric zonal neutral wind velocities obtained from the HWM-90 model (Hedin et al., 1991) to investigate the thermosphere-ionosphere coupling. Salient features from this study are presented and discussed.

Key words. Ionosphere (ionosphere-atmosphere interactions; ionospheric irregularities; instruments and techniques)

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