|
|
 |
|
|
Ann. Geophys., 21, 2315-2322, 2003
www.ann-geophys.net/21/2315/2003/
© European Geosciences Union 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
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)
Full Article in PDF (710 KB) |
|
|
