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.

This work presents an analysis of the scintillation onset over the southern Brazil based on data from two solar maximum periods and simulation of the ionospheric conditions before the scintillation onset. The results shows some patterns which may help to prevent several satellite-based technological applications suffering disruptions due to scintillation issues.

We have analyzed the low-latitude ionospheric responses to solar flares. In particular we show for the first time that 5 to 8 min of time delay is present in the peak effect in the EEJ, with respect that of S_q current outside the magnetic equator, in response to the flare radiation enhancement. We propose that the flare induced enhancement in neutral wind occurring with a time delay could be responsible for a delayed zonal electric field disturbance driving the EEJ.

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.