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.

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.

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.