Spatial Correlation Analysis of Ionospheric Delays at Different Spatial Scales

The spatial correlation of ionospheric delays is a crucial factor influencing the accuracy of satellite-based navigation systems such as GNSS. Using data from 317 Continuously Operating Reference Stations (CORS) in North America for the year 2017, the analysis investigates ionospheric delay variability across small and large spatial scales. Small-scale variability is quantified through standard deviation calculations of delay differences, while large-scale trends are modeled using a linear relationship between delay variance and distance. The analysis considers both geomagnetically quiet and disturbed conditions, with a focus on the geomagnetic storm in September 2017. Results indicate that small-scale variability remains stable even under disturbed conditions, while larger-scale trends show significant increases in delay variability during geomagnetic storms. Furthermore, the study identifies the critical distance at which the contributions from variability and trend components balance, with this distance increasing during geomagnetic storms. These findings provide valuable insights into ionospheric behavior, highlighting its impact on the performance of satellite navigation systems, especially under disturbed ionospheric conditions.