Determinação do vento horizontal a partir de observações de ondas de gravidade.

Abstract

Nightglow images of an all-sky imager from all over the sky installed in São João do Cariri (7.4° S, 36.5° W), from January to December 2005, were used to study almost orthogonal gravitational waves. These are gravity waves that occur simultaneously, propagating with phase fronts that are almost perpendicular to each other. During this period, 135 nights were investigated and 9 events were observed for the year 2005. The waves were observed in two emission lines, the OH meinel band and the green line OI 5577 emission line. The observed parameters of these wave waves (horizontal and vertical wavelength, direction of propagation and observed period) were studied to estimate the background wind in the direction of the waves using the Doppler shift at the observed frequency to find the wind. The intrinsic frequency was evaluated using an inelastic Taylor-Goldstein dispersion relation for gravity waves. The observed waves had a period between 4 and 23 minutes and a horizontal wavelength between 15 and 30 km. The observed wavelength was between 14 and 17 km, while the phase speed varied from 20 to 45 m/s. The majority of gravitational waves were observed after 2000 hours UT and the direction of propagation was predominantly east and southeast, originating from the northwest. The estimated wind velocity showed good agreement with the real wind velocity detected by the meteor radar also located at São Jõao do Cariri. It has been shown that it is possible to estimate, with a fair degree of accuracy, the background wind velocity in the direction of the gravity waves using coincident data from three different instruments simultaneously.