GPS TEC Observations of Storm Time Large Amplitude ULF Pulsations

Decades ago Davies and Hartmann [1976] demonstrated the ability to detect ULF waves by monitoring the carrier phase of trans-ionospheric radio waves (from geosynchronous satellites). This study was followed by several theoretical and modeling studies that addressed the physical mechanisms behind the observations. However, since then there have been relatively few studies that have utilized this observational technique to advance our understanding of ULF waves or to fully understand the mechanisms that lead to the observed variations in electron content. Here, we investigate large amplitude (> 500 nT) ULF pulsations observed during the October 31, 2003 storm using GPS TEC. This event has been recently examined by Pilipenko et al. using the EISCAT radar facility and we find that the observed variations in GPS TEC closely match the variations in electron density observed by the radar. Furthermore, we show that the GPS TEC observations provide the ability to monitor the two dimensional structure of these waves on a global scale; a capability that compliments similar capabilities of networks of ground-based magnetometers. The combination of these two data sets may significantly contribute to our understanding of the associated field-aligned current systems.