GPS Positioning Performance in the Wake of the Halloween 2003 Geomagnetic Storm

Severe space weather events are well known as the causes of considerable disruptions of the GPS positioning service. Manifested as geomagnetic and ionospheric storms, severe space weather affects the amount of the GPS ionospheric delay, which has been identified as the most important cause of GPS positioning error. Although the standard GPS positioning service offers the error compensation algorithm (called Klobuchar ionospheric model), studies showed it does not provide sufficient performance improvement, especially during severe space weather conditions. Space weather effects on GPS ionospheric delay have been studied in different parts of the world in order to establish local, regional and even global models of GPS ionospheric delay corrections. However, studies addressing the impact of severe space weather conditions on the actual GPS positioning performance are less abundant. Here we report the GPS positioning performance observed in Osijek, Croatia in the wake of severe space weather disruption and geomagnetic storm occurred on 29 and 30 October 2003, an event also known as the Halloween 2003 event. The archived single-frequency GPS pseudorange measurements taken at the reference GPS site at Osijek, Croatia were used in analysis of GPS positioning performance. Statistical properties (mean, median, standard deviation, kurtosis) of GPS northing, easting and height errors were calculated for every day in time interval 13 October 2003 - 3 November 2003 with reference to actual position of the Osijek reference station. Time series of GPS positioning errors statistical parameters were correlated with time series of space weather-related parameters (sunspot number and solar flux, as descriptor of solar activity, and planetary Ap index, as a descriptor of geomagnetic conditions). Results of the analysis show noticeable of effects of height and north GPS positioning error components, while the east GPS positioning component remained almost unaffected. Further work will focus on investigation of correlation between statistical descriptors of the GPS positioning performance and space weather parameters.