The contribution to the project of the National Research Council of Italy (CNR) based in Florence (i.e., from the Complex System Institute, ISC, and the Applied Physics Institute "Nello Carrara", IFAC) is a study on the role of Total Electron Content (hereafter TEC) data from a LEO satellite in space weather. Note that both RO data and navigational data are included in the study of TEC data from LEO satellites. This study plans to cover three tasks: A quantitative assessment of how processing TEC data from a LEO improves the retrieval of ionospheric profiles via stochastic inversion techniques (SIT); a study of how the navigational TEC data from a LEO satellite may be used to monitor the space weather; a study of the fine structure of the ionosphere by analyzing the fine structure of the RO data. Since real TEC data from the ROSA receiver will be available only in the future, currently our investigations are carried out on data from other LEOs (CHAMP and Formosat-3/COSMIC), assuming it will be sensible to apply these achievements to ROSA data. The study on the retrieval of ionospheric vertical profiles via a SIT consists of assessing the improvement brought by involving RO data, optimizing the inversion parameters in the SIT with RO and studying the assimilation of GPS, ROSA, and ionosonde data (this last item could lead to real time inversion). The profiles Ne(h) retrieved via SIT will be compared with independent measurements of related quantities, e.g., from ionosondes. TEC data used will be those from the GPS network and CHAMP, while ionosonde data will come from the Space Physics Interactive Data
Resource (SPIDR) website and the European Digital Upper Atmosphere Server network (DIAS). Real data from ROSA will be used as soon as available.
The purpose of our second research line is the assessment of the possibility of monitoring the response of the geospace to heliophysical events by using the navigational data from GPS receivers onboard a LEO, giving information about the topside part of the ionosphere and the plasmasphere. In this framework we are going to build a dynamical picture of Sun-geospace interaction, working mainly on "historical" data series as those from the TOPEX mission. Then, these findings will be applied to the already existing LEO data base (CHAMP and Formosat-3/COSMIC), and then to the real data from ROSA. Ionospheric irregularities are studied analyzing the RO data from LEOs at a time scale as small as possible, and sensible. With a suitably high sampling frequency (e.g., 50 Hz for the GPS ground receivers) it would be possible to detect very small scale structures inducing radio scintillation, which may not be the case of ROSA. However, the present investigation is focused on the development of suitable data analysis tools to process non-stationary signals with a rich multi-scale structure, as those due to the "intermittent" nature of the plasma distribution that generates them. The tool chosen is the wavelet analysis. Investigating the small scale structure of the ionospheric medium by analyzing RO data from a LEO will be useful for two purposes: On the one hand one might make a comparison between the radio scintillations of mainly ionospheric origin (from ground GPS receivers) and that of mainly low-ionospheric or tropospheric origin (the RO data from a LEO), on the other hand, even if the sampling time of the LEO data would not be enough for scintillation studies, however the wavelet analysis of RO data will render it possible to understand the vertical distribution of the ionosphere irregularities.
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