When meteoroids enter in the Earth's atmosphere, they form ionized meteor trails, which have been used for terrestrial atmospheric dynamic studies by radar techniques for more than 80 years. After its formation, the trail is dissipated mainly by ambipolar diffusion causing an exponential decrease in the echo amplitude. The signal decay constant is inversely proportional to the ambipolar diffusion coefficient, which depends on the atmospheric environment temperature and density. Recently, the decay time of the meteor echoes has been used to estimate the mesopause temperatures in northern middle and high latitudes. In this work, the decay time data, obtained by meteor radar from August-2004 to December-2007 at São João do Cariri (7.4°S, 36.5°W), were used to estimate the equatorial mesopause temperature. The results obtained during the observation period suggest that the mesopause temperature presents a semi-annual behavior, with maximum temperatures in the autumn and austral spring months, and minimum during austral summer and winter months.
mesospheric temperature; ambipolar diffusion; meteor radar
