Contiguous Space-time TEC Enhancements in JPL GIMs - Seasonal, Latitudinal and Activity dependence

The variability of GPS positioning and timings impacts navigation, communication and other low-Earth orbit satellites and is affected by space weather. Ground GNSS observations of Total Electron Content (TEC) with 100 − 200 ground stations are used to compile global maps of TEC to monitor ionospheric response to space weather events. We consider Global Ionospheric Maps (GIMs) available at a 15-minute cadence and a spatial resolution of 1 × 1 degree longitide/latitude bins from the Jet Propulsion Laboratory (JPL). These are available over 2 solar cycles, providing an extensive data set covering both seasonal variation and quiet/active times. Our study uses feature extraction to identify regions of enhanced TEC that are contiguous in both space and time. For each map, we identify spatially contiguous High Density Regions (HDRs) as the region on the TEC map within which the level is exceeded by the top 1% of TEC values. We then apply a tracking algorithm over consecutive timestamps to obtain a set of labelled coherent space-time TEC HDRs. Extracting and following these HDRs over multiple years allows us to explore their statistical dependencies upon geomagnetic activity, latitude and season. Given a set of geomagnetic indices (Dst, Kp and/or F10.7) at some date-time, we can determine the locations of HDRs, how long they last and their size/brightness. Our analysis detects, labels and tracks HDR origin, path, areas, TEC intensities and duration. TEC estimation in the JPL data has higher accuracy over the continental US and Europe than in other areas. We consider how this non-uniform distribution of ground stations affect our results.