Mid-latitude Ionosphere Variability (2013–2016), and Space Weather Impact on VTEC and Precise Point Positioning

Abstract

The dominant error source for Global Navigation Satellite Systems (GNSS) is the ionosphere, especially during strong solar activity and space weather. Using dual-frequency GNSS observations, the integral of the electron density along a GNSS signal in the ionosphere can be estimated. For research and practical applications, this is usually mapped to the Vertical Total Electron Content (VTEC). VTEC is used to study and monitor the ionosphere, and correct ionosphere effects that degrade the accuracy and reliability of GNSS positioning. For the first time, this paper represents detailed study of the VTEC variability for Bosnia and Herzegovina by analyzing daily, monthly, seasonal, solar cycle and space weather-related VTEC variations for a 4-year period, i.e. from 2013 to 2016. VTEC values were derived from GNSS observations of the EUREF Permanent Network (EPN) station SRJV, located in Sarajevo (43.8679N, 18.4139E). VTEC varied according to solar activity and solar cycle progression. The largest VTEC values and standard deviations occurred during spring equinox. Moreover, ionospheric winter anomaly was observed during high solar activity. Furthermore, the impact of a severe St. Patrick’s geomagnetic storm in March 2015 was studied in terms of VTEC variations and dual-frequency Precise Point Positioning (PPP). During a storm, VTEC values change from about 50% to 150% with respect to the mean VTEC of quiet days. Artificial coordinate variations were visible in all three components (north, east and up), where the highest position error was up to 0.2 m in the up component.