Special issue  

Using the Digisonde data, this paper shows that the small variation in the geomagnetic activity during low solar activity can affect both the parameter of height and frequency of the intermediate layer (ILs) over the low latitude Brazilian sector. The most expressive responses of the ILs to geomagnetic activity were during the summer when the height of the ILs suffered a significant decrease with the increase of the magnetic activity magnetic in the first hours of the day.

In the present work, the lunar semidiurnal tide (M₂) was investigated in the equatorial plasma bubble (EPB) zonal drifts over Brazil from 2000 to 2007. On average, the M₂ contributes 5.6 % to the variability of the EPB zonal drifts. It was also observed a strong seasonal and solar cycle dependency, being the amplitudes of the M₂ stronger during the summer and high solar activity periods.