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Ann. Geophys., 24, 3343-3350, 2006
www.ann-geophys.net/24/3343/2006/
© European Geosciences Union 2006
Signatures of 3–6 day planetary waves in the equatorial mesosphere and ionosphere
H. Takahashi1, C. M. Wrasse1, D. Pancheva2, M. A. Abdu1, I. S. Batista1, L. M. Lima3, P. P. Batista1, B. R. Clemesha1, and K. Shiokawa4
1Instituto Nacional de Pesquisas Espaciais, INPE, CP-515, 12245-970 São José dos Campos, SP, Brazil
2Department of Electronic & Electrical Engineering, University of Bath, Bath, BA2 7AY, UK
3Dept. Física, Universidade Estadual de Paraíba, Campina Grande, PB, Brazil
4Solar Terrestrial Environmental Laboratory, STEL, Nagoya University, Toyokawa, Aichi 442-8507, Japan
Abstract. Common periodic oscillations have been observed in meteor radar measurements
of the MLT winds at Cariri (7.4° S, 36.5° W) and Ascension Island
(7.9° S, 14.4° W) and in the minimum ionospheric virtual height, h'F,
measured at Fortaleza (3.9° S, 38.4° W) in 2004, all located in the
near equatorial region. Wavelet analysis of these time series reveals that
there are 3–4-day, 6–8-day and 12–16-day oscillations in the zonal winds and
h'F. The 3–4 day oscillation appeared as a form of a wave packet from 7–17 August 2004.
From the wave characteristics analyzed this might be a 3.5-day
Ultra Fast Kelvin wave. The 6-day oscillation in the mesosphere was
prominent during the period of August to November. In the ionosphere,
however, it was apparent only in November. Spectral analysis suggests that
this might be a 6.5-day wave previously identified. The 3.5-day and 6.5-day
waves in the ionosphere could have important roles in the initiation of
equatorial spread F (plasma bubble). These waves might modulate the
post-sunset E×B uplifting of the base of the F-layer via the induced lower
thermosphere zonal wind and/or the E-region conductivity.
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