Observações de Ondas de Gravidade de Méedia Escala na Região Equatorial do Brasil

Using images of the OHNIR airglow emission over S˜ao Jo˜ao do Cariri (7:4oS; 36:5oW) during the second Spread-F Experiment (SpreadFEx), from September to November 2009, 26 medium-scale gravity waves (MSGW) were observed, and their observed parameters were estimated. Simultaneous measurements of the mesospheric winds and temperature [obtained by a meteor radar and an OH(6,2) photometer, respectively] were used to calculate the intrinsic parameters of these waves. The characteristics of these waves, in general, are similar to it was observed during the first campaign. Most waves presented wavelengths between 50 and 150 km, periods from 20 to 100 min, and phase between 20 m/s and 80 m/s, propagating eastward. The intrinsic parameters revel that the wind may reduce the phase speeds. Most waves had vertical wavelength smaller than 20 km. Furthermore, two MSGWs presented an unusual intrinsic phase speed, i.e, they were faster than 85 m/s. These two waves have a potential to reach altitudes higher than 150 km, and, consequently, they may be more powerful in seeding equatorial spread F.