Characteristics of the ionospheric irregularities over Brazilian longitudinal sector

Based on the data obtained from a network of GPS L1 band receivers deployed in Brazil, we present here the characteristics of the 400 m ionospheric irregularities during magnetically quiet and disturbed conditions.The network is composed of 12 GPS scintillation monitors and covers the latitudinal region from the magnetic equator up to the southern crest of the Equatorial Ionization Anomaly (EIA), which is characterized by large horizontal gradients in the electron density distribution. Some results on equatorial spread F statistics obtained from digisonde data over Cachoeira Paulista (22.41 o S, 45 o W, dip latitude 14.89 o S) and from ionosonde data over Tucumán (64.5 o W, 27 o S, dip latitude 13.71 o S) are also used in this work to complement the results from GPS network. The effects of local time, season, latitude, longitude, background ionization, solar cycle and magnetic activity on the ionospheric irregularities are presented. The ionospheric irregularity zonal velocities determined by magnetically east-west spaced GPS receivers are also presented. The influence of the ionospheric irregularities on GPS based navigational systems is discussed. These observations, complemented by computational simulations, may improve our understanding of the factors responsible for the generation, growth and dynamics of the equatorial F region plasma irregularities .

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