Imaging of the equatorial ionospheric anomaly over South America - A simulation study of total electron content

Imaging the equatorial ionosphere in three dimensions is challenging due to the high diurnal variations at low latitudes. Inversions of total electron content (TEC) together with model-derived TEC data as replacement of measurement data along satellite-to-ground paths allow reconstructing electron densities. The technique is tested using a realistic simulation study, where the ionosphere is modelled using the International Reference Ionosphere model and actual satellite and receiver locations are used to simulate the data that can be collected over the South American region. The multi-instrument data analysis system (MIDAS) algorithm is used, where reconstructions are based on defining the sample space of stochastic inversions by empirical orthonormal functions (EOFs), that need to be adjusted depending on region, time and geophysical conditions studied. Insight into information supporting vertical ionospheric reconstructions and suitable horizontal receiver constellations allows to create reliable images of low (mean and maximum) TEC errors. The technique is potentially of interest for physical studies of the anomaly, particularly under storm events when its morphology deviates from normal. (C) 2006 Elsevier Ltd. All rights reserved.