The investigators will deploy five Global Positioning System (GPS) receivers in South America to observe the day-to-day variability of the equatorial ionosphere. They will use the data to study the background ionospheric conditions leading to the development of equatorial spread F (ESF). The goal is to understand the combined action of the number density, plasma drifts, neutral winds, and electric fields in relation to irregularity formation. The five receivers will add to an existing network of 12, providing an unprecedented latitudinal range for observing equatorial plasma phenomena. The measurement of total electron content provided by the receivers will be used to determine the vertical profiles of electron density using tomographic inversion techniques. To interpret the data, the investigators will develop a theoretical model of the low latitude ionosphere whose output can be compared with the measurements. This combination of model and measurements will be applied to events covering different seasons, magnetic conditions, and solar activity levels. The results will be used to improve Space Weather forecasts of the mid-latitude ionosphere to reduce the impact on navigation and communication systems resulting from ionospheric irregularities.
