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. Periodic waves were observed in the OI6300 airglow images over SaoJoao do Cariri (36.5 ∘  W, 7.4 ∘  S) from 2012 to2014 with simultaneous observations of the thermospheric wind usingtwo Fabry–Perot interferometers (FPIs). The FPIs measurements were carried outat Sao Joao do Cariri and Cajazeiras (38.5 ∘  W,6.9 ∘  S). The observed spectral characteristics of thesewaves (period and wavelength) as well the propagation direction were estimatedusing two-dimensional Fourier analysis in theairglow images. The horizontal thermospheric wind was calculatedfrom the Doppler shift of the OI6300 data extracted from interferencefringes registered by the FPIs. Combining these two techniques, theintrinsic parameters of the periodic waves were estimated andanalyzed. The spectral parameters of the periodic waves were quitesimilar to the previous observations at Sao Joao do Cariri. Theintrinsic periods for most of the waves were shorter than theobserved periods, as a consequence, the intrinsic phase speeds werefaster compared to the observed phase speeds. As a consequence, thesewaves can easily propagate into the thermosphere–ionosphere sincethe fast gravity waves can skip turning and critical levels. Thestrength and direction of the wind vector in the thermosphere must bethe main cause for the observed anisotropy in the propagationdirection of the periodic waves, even if the sources of these wavesare assumed to be isotropic. Keywords. Meteorology and atmospheric dynamics (waves and tides)

Intrinsic parameters of periodic waves observed in the OI6300 airglow layer over the Brazilian equatorial region