Statistical Properties of Quiet Space Weather Northern Adriatic Residual GPS Ionospheric Delay

In this paper the analysis results of statistical properties of quiet space weather Northern Adriatic residual GPS ionospheric delay time series are presented with the aim to describe the nature of the residual GPS ionospheric delay and thus provide a foundation for improvements of previously established Klobuchar - luike NA-QSW model.In addition , perfomance of the NA-QSW model is compared with the perfomance of the European NeQuick model .A case study of quiet space weather and general ionospheric conditions in Summer 2007 has been chosen for a comparative analysis.The results of the analysis show a fair perfomance of Klobuchar-like NA-QSW model. Statistical analysis of residual GPS ionospheric delays reveals the NA-QSW model performs even better than the standard European NeQuick model.In addition , it suggests several improvements of the NA-QSW model to be made in order to achieve the normal distribution of the residual GPS ionospheric delays.This will eventually lead towards establishment of a three - component (linear night time, cosine day time and stohastic with known statistical distribution) GPS ionospheric model for the Adriatic Sea are.