GPS TEC and Riometer Techniques for Observing Absorption Events in the High Latitude Ionosphere

Structures of enhanced ionization are a ubiquitous feature of the high latitude ionosphere and can significantly affect the propagation of trans-ionospheric radio waves. Using Global Positioning System (GPS) receivers and co-located riometers, I have concurrently examined variations in GPS total electron content (TEC) and 30 MHz radio absorption associated with enhanced ionization. A survey of 128 events revealed four clear TEC-absorption relationships based on the source mechanism of the ionization and the nature of the measurements. These relationships also agreed with theoretical predictions.;Using a unique TEC-absorption relationship for substorm particle injection, I have also identified signatures of particle injection in TEC. Since multi-satellite data is available to each GPS receiver, these signatures can be used to track an injection region at a higher resolution than previously available. By applying this technique, I have calculated the poleward expansion speed of the injection region for two separate substorm events.