Dynamics of Space-Time TEC Enhancements seen in JPL GIMs: Variations with Latitude, Season and Geomagnetic Activity

Total Electron Content (TEC) is broadly used in characterizing ionospheric response to solar and geomagnetic activity. Understanding how TEC structures vary over time can help mitigate the risks of space weather events to navigation and communication systems. Global Ionospheric Maps (GIMs) produced by the Jet Propulsion Laboratory (JPL) provide 20 years of GNSS observations at a spatial resolution of 1^◦ × 1^◦ longitude/latitude and temporal resolution of 15 minutes. We transform each of these maps into geomagnetic coordinates centered about the sub-solar point and isolate the top 1% of TEC values to define High Density Regions (HDRs) of TEC. We demonstrate how this quantile threshold of TEC varies over the 20 year data set. Using image processing tools we have constructed an algorithm that detects and tracks HDRs to identify a population of contiguous, uniquely labelled 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. We find that HDRs naturally divide into two populations by peak area, separated by an intensification area of 8.0×10⁶km², which is around the continental scale. These populations are studied for different storm conditions - quiet (Kp < 4), moderate (4 ≤ Kp < 7) and extreme (Kp ≥ 7). Small HDRs form primarily in four magnetic latitude clusters and move approximately along lines of constant magnetic latitude. Continental scale HDRs form around the same latitudes as small HDRs but follow more complex paths. The statistical nature of our results may inform predictive ionospheric models and reveal reproducible trends in the formation and subsequent propagation paths of ionospheric enhancements.