Statistical Analysis of Ultra Low Frequency Total Electron Content Disturbances: Relationship to Magnetospheric Waves

Disturbances in ionospheric Total Electron Content (dTEC) with timescales of ∼10s-1000s can be driven from above by processes in the magnetosphere and below by processes on the Earth’s surface and lower atmosphere. Past studies showed the potential of dTEC as a diagnostic of magnetospheric Ultra Low Frequency (ULF) wave activity and demonstrated that ULF dTEC can impact space weather by, for example, changing ionospheric conductance. However, most past work has focused on single event studies, lacked magnetospheric context, or used sampling rates too low to capture most ULF waves. Here, we perform a statistical study using Time History of Events and Macrsoscale Interactions during Substorms (THEMIS) satellite conjunctions with a ground-based magnetometer and Global Navigation Satellite System (GNSS) receiver at ∼65 degrees magnetic latitude. We find that magnetospheric ULF waves generate dTEC variations across the broad range of periods examined in this study (∼20-500s), and that ULF dTEC wave power is correlated with Kp, AE, solar wind speed, and satellite and ground magnetic field wave power. We further find that magnetospheric ULF waves generate dTEC amplitudes up to ∼ 5 TECU (∼ 30 − 40% background), with the largest amplitudes occurring during geomagnetically active conditions, at frequencies below 7 mHz, and at local times near midnight. We finally discuss the implications of our results for magnetosphere ionosphere coupling and remote sensing techniques related to ULF waves.