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Abstract. Airglow and wind measurements from the Brazilian equatorial region were used to investigate the presence and the effects of the 3-4-day ultrafast Kelvin waves in the MLT. The airglow integrated intensities of the OI557.7 nm, O 2 b(0-1) and OH(6-2) emissions, as well as the OH rotational temperature, were measured by a multichannel photometer, and the zonal and meridional wind components between 80 and 100 km were obtained from a meteor radar. Both instruments are installed in the Brazilian equatorial region at São João do Cariri (7.4 • S, 36.5 • W). Data from 2005 were used in this study. The 3-4-day oscillations appear intermittently throughout the year in the airglow. They were identified in January, March, July, August and October-November observations. The amplitudes induced by the waves in the airglow range from 26 to 40 % in the OI557.7 nm, 17 to 43 % in the O 2 b(0-1) and 15 to 20 % in the OH(6-2) emissions. In the OH rotational temperature, the amplitudes were from 4 to 6 K. Common 3-4-day oscillations between airglow and neutral wind compatible with ultrafast Kelvin waves were observed in March, August and October-November. In these cases, the amplitudes in the zonal wind were found to be between 22 and 28 m s −1 and the vertical wavelength ranges from 44 to 62 km. Evidence of the nonlinear interaction between the ultrafast Kelvin wave and diurnal tide was observed.

Abstract. The planetary-wave-induced airglow variability in the mesosphere and lower thermosphere (MLT) is investigated using simulations with the general circulation model (GCM) of Kyushu University. The model capabilities enable us to simulate the MLT OI557.7 nm, O 2 b(0-1), and OH(6-2) emissions. The simulations were performed for the lowerboundary meteorological conditions of 2005. The spectral analysis reveals that at middle latitudes, oscillations of the emission rates with the period of 2-20 days appear throughout the year. The 2-day oscillations are prominent in the summer and the 5-, 10-, and 16-day oscillations dominate from the autumn to spring equinoxes. The maximal amplitude of the variations induced by the planetary waves was 34 % in OI557.7 nm, 17 % in O 2 b(0-1), and 8 % in OH(6-2). The results were compared to those observed in the middle latitudes. The GCM simulations also enabled us to investigate vertical transport processes and their effects on the emission layers. The vertical transport of atomic oxygen exhibits similar periodic variations to those observed in the emission layers induced by the planetary waves. The results also show that the vertical advection of atomic oxygen due to the wave motion is an important factor in the signatures of the planetary waves in the emission rates.

Electric fields associated with MSTID can intensify the growth of the Equatorial Plasma Bubble.q Partial inhibition of the Equatorial Plasma Bubble by MSTID occurs after the bubble intensifies and bifurcates.

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Abstract. We observed a gravity wave (GW) signature in the OH emission layer in the upper mesosphere, and 4 hours later, a medium-scale traveling ionospheric disturbance (MSTID) in the OI 630 nm emission layer. Spectral analysis of the two waves did show that both have the same wave characteristics: wavelength, period, phase speed and propagation direction, respectively, 200 km, 60 min, 50 m/s, propagating southeastward. During the MSTID occurrence, concentric wavefronts were also observed in the ionosphere by detrended total electron content (dTEC) maps. From the gravity wave ray-tracing simulation for the mesospheric gravity wave, we found that the wave came from a tropospheric deep convection spot and propagated up to the 140 km altitude. Regarding the same wave characteristics between mesospheric GW and MSTID, two possible cases are investigated: a direct influence of the GW oscillation in the OI 630 nm emission height and the generation of a secondary wave during the GW breaking process. The concentric wave structure suggests the generation of a secondary wave after the primary wave was dissipated in the lower thermosphere. This is the first time to report an observational event of gravity wave propagation from the troposphere, mesosphere to thermosphere-ionosphere in the south American region.

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