IGPP Seminar Series

Tsunami Signatures Observed in the Ionosphere

by David Galvan
Jet Propulsion Laboratory

Abstract

Tsunami Signatures Observed in the Ionosphere Movements of the Earth’s surface can influence the upper atmosphere through atmospheric waves of pressure and density. Tsunami oscillation periods are sufficiently long (5 minutes to over an hour) to produce atmospheric internal gravity waves that propagate up to the ionosphere, creating disturbances in ionospheric electron density that travel horizontally with the ocean waves below. These traveling ionospheric disturbances can be observed using measurements of integrated ionospheric electron density (known as total electron content, or TEC) between Global Positioning System (GPS) satellites and receivers on the ground. These GPS TEC observations show variations consistent with tsunami-driven internal gravity waves in several recent events we have studies: the American Samoa tsunami of September 29, 2009, the Chile tsunami of February 27, 2010, and the devastating Japan tsunami of March 11, 2011. Fluctuations in TEC correlated in time, space, and wave properties with these tsunamis were observed in TEC estimates processed using JPL’s Global Ionospheric Mapping Software. These TEC estimates were band-pass filtered to remove variations with wavelengths and periods outside the typical range of internal gravity waves caused by tsunamis. Significant TEC variations were not always seen when a tsunami was present, but the regions where a strong tsunami was observed coincided with clear TEC variations, while a lack of clear TEC variations coincided with smaller tsunami amplitudes. Where variations were observed, the typical amplitude tends to be on the order of 1% of the background TEC measurement. These observations are compared to estimates of TEC variations produced by Embry Riddle Aeronautical University’s Spectral Full Wave Model, an atmosphere-ionosphere coupling model, and found to be in reasonable agreement. The potential exists to apply these detection techniques to real-time GPS TEC data, providing estimates of tsunami speed and intensity that may be useful for early warning systems.
Tuesday, 12 April 2011
3853 Slichter Hall
Refreshments at 3:45 PM
Lecture at 4:00 PM