A Study of Pc4-5 Geomagnetic Pulsations in the Brazilian Sector
  This paper presents a study of Pc4-5 geomagnetic pulsations illustrated by those which were observed after the sudden commencement of May 02 of 2010 at 09 : 08 UT at the Brazilian stations TTB, VSS and SMS. We carry out the spectral analysis of a bivariate data using the Morse wavelets and calculate polarization attributes (ellipticity ratio, tilt angle and phase difference) in the time-frequency domain. The main pulsation wave packets occurred, for the selected day, around noon and a small enhancement of the pulsation amplitude is observed in the TTB station. A change in the pulsation polarization has been found for the TTB station, which we have attributed to effects of the equatorial electrojet. 
David Oliva, Marcela C. Meirelles and Andr\'es R. R. Papa
physics.space-ph