Space-Based Remote Sensing of Natural-Hazard-Induced Ionosphere-Thermosphere Perturbations

We present the first Gravity Recovery and Climate Experiment (GRACE) observations of the ionosphere-thermosphere perturbations associated with upper atmosphere infrasound propagation induced by natural hazard events. Total electron content (TEC) and neutral air density perturbations retrieved from NASA's GRACE measurements have been found to be in good agreement with the results from a ground-based dense GPS network, infrasound array and seismic stations. Significant TEC fluctuations and air-density perturbations, up to 6% and 4% of ambient background values respectively, were observed at the GRACE orbital altitude 8 minutes after the arrival of the seismic and infrasound waves. Wavefront arrival times are consistent with the Global Ionosphere-Thermosphere Model (GITM) and infrasound ray-tracing modeling results. This is the first time, to the best of our knowledge, that natural-hazard-induced ionosphere-thermosphere perturbation signatures were measured directly at 450 km altitude. We envision that space-based neutral and electron density perturbations will be an important contributor in future early warning systems of natural hazards.