Equatorial ionospheric irregularities have a significant detrimental impact on a variety of space application systems in navigation and communication areas that utilize satellites, especially the Global Navigation Satellite Systems (GNSS) network. The development of these irregularities in the nighttime ionosphere is controlled primarily by ionospheric electric fields and instabilities. The effect of magnetic disturbance on these electric fields and on the irregularities is investigated here.

The relationship between the tropospheric convection and the ionospheric phenomenology have been investigated in recent decades. In this work a relation between the lightning strike activity and the characteristics of the equatorial spread-F events is analyzed over the Brazilian region, and the results seem to support the hypothesis of some indirect interrelationship between both distinct phenomena.

The total electron content (TEC) is being extensively used to monitor the ionospheric behavior under geomagnetically quiet and disturbed conditions. The TEC presents significant changes during geomagnetic disturbed periods, causing degradation of signals in navigation systems and satellite communication. The geomagnetically disturbed periods occur due to enhanced solar activity and we show that the TEC presents intensifications not only during geomagnetic storms but also during HILDCAA events.

This paper analyzes the influence of the recent deep and prolonged solar minimum on the daytime zonal and vertical plasma drift velocities during quiet time over Jicamarca, Peru. Our results show that an anomalously low zonal wind was mainly responsible for the observed anomalous behavior in the zonal drift followed by a decrease in the E-region conductivity and the dynamo electric field during 2008.

In this study we analyzed ~ 17 years of GPS data from receivers installed in the observatory of Cachoeira Paulista, Brazil. We statistically analyzed the occurrence of GPS signal amplitude fluctuations caused by irregularities in the Earth's upper atmosphere. These signal fluctuations are known to provoke positional errors for GPS users. The results revealed that the secular variations in the Earth’s magnetic field are affecting the climatology of such GPS signal fluctuations.

In this work the response of the Brazilian equatorial ionosphere is studied during three HILDCAA events that occurred in the year of 2006 using the digisonde data. Geomagnetic indices and interplanetary parameters were used to calculate a cross-correlation coefficient between the E_y and the hmF2. The results showed that the pumping action of particle precipitation into the auroral zone has moderately modified the equatorial hmF2, being more sensitive during PRE time.

We present results of Capon's method for the estimation of in-beam images of equatorial spread F (ESF) irregularities observed by the São Luís radar interferometer. Results of numerical simulations show that, despite the short baselines of the system, the method is capable of distinguishing localized features with kilometric scale sizes (zonal direction). Results from the application of Capon’s method to actual measurements show that it is able to resolve features expected to occur in ESF.

Periodic waves have been observed over São João do Cariri during almost one solar cycle. Similarities between the characteristics of these events with observations at other places around the world were noted, primarily the spectral parameters. Most observed waves have appeared during magnetically quiet nights, and the occurrence of those waves followed the solar activity. Due to their characteristics, most of them must have had different generation mechanisms from the Perkins instability.