Ionospheric scintillation challenges the GNSS positioning performance with its stochastic nature, preventing development of easily implementable correction model. Initially understood as related to polar and equatorial regions, the ionospheric scintillation effects have been identified in mid-latitudes as well, thus affecting rising number of GNSS-founded applications (systems and services). Here we contribute to the problem solution with presentation of the research aimed at statistical analysis of the S4 amplitude ionospheric scintillation index time series were created from dual-frequency GPS observations (raw pseudoranges and navigation messages) collected in Poreč, Croatia during the ionospheric event. The S4 time series were analysed statistically to identify potential GNSS-related effects, and to estimate their statistical distribution, thus establishing foundations for the S4 stochastic model development for a rapid ionospheric storm. Research conducted found modified statistical characteristics of the S4 time series, and identified the statistical distribution estimate using the Cullen and Fray graph method, with all the processing performed with bespoke software developed in the open-source R framework for statistical computing. Research results will form foundation for continuation of our research aimed at development of the S4/ionospheric scintillation stochastic model for the Adriatic Sea, and the assessment of the effects of ionospheric scintillation on GNSS positioning performance in the region under observation.

Keywords: GNSS, ionospheric scintillation, statistical model, ionospheric storm