3-4 day Kelvin waves observed in the MLT region at 7.4° S, Brazil

Abstract

Meteor wind measurements obtained from São João do Cariri–PB (7.4° S, 36.5° W), Brazil, during 2005, have been used to examine the ultra–fast Kelvin wave characteristics in the mesopause and lower thermosphere region. The hourly winds were subjected to wavelet analysis and the results revealed the presence of 3–4 day oscillation in four episodes along the year. The observed parameters were used to check if the 3–4 days oscillations satisfy the dispersion relation for Kelvin waves. The results showed that only the oscillations that occurred in February–March and May–June (first and second events), are compatible with equatorial ultra–fast Kelvin wave propagation, with zonal wave number s=1. During these two events, the zonal wind amplitudes reached maximum values of 25 m/s and 20 m/s respectively. The vertical phase structure showed descending phase, compatible with ascending wave energy, and vertical wavelengths of about 40 km were found for both events.