CEDAR-GEM Joint Workshop

Ocean tsunami wavelengths are sufficiently long to produce atmospheric internal gravity waves that propagate to the ionosphere, creating disturbances in ionospheric electron density that travel with the ocean waves below. These traveling ionospheric disturbances (TIDs) can be observed using measurements of integrated ionospheric electron density (also known as total electron content, or TEC) between Global Positioning System (GPS) satellites and GPS receivers on the ground. GPS receivers onboard satellites in low Earth orbit, such as in the COSMIC constellation of radio-occultation measurement satellites, may also be useful in observing these tsunami-driven TIDs. Ground-based GPS TEC observations show variations consistent with tsunami-driven internal gravity waves in several recent events we have investigated, including the Japan tsunami of March 2011. Fluctuations in TEC correlated in time, space, and wave properties of these tsunamis were observed in TEC estimates processed using JPL’s Global Ionospheric Mapping Software Suite. The TEC estimates were band-pass filtered to remove variations with wavelengths and periods outside the typical range of internal gravity waves caused by tsunamis. Observed ionospheric TIDs were correlated with the speed, direction, and wavelength of ocean surface tsunami waves as measured by Deep-ocean Assessment and Reporting of Tsunamis (DART) buoys, and simulated by the NOAA’s Method of Splitting Tsunami (MOST) model and JPL’s Song model. The typical amplitude of ionospheric variation was on the order of 1% of the background TEC measurement for waves far afield from the epicenter, and up to 10% of the background TEC for waves close to the epicenter in the case of the Japan event of March 2011. These observations are compared to estimates of TEC perturbations produced by the Embry Riddle Aeronautical University’s Spectral Full Wave Model, an atmosphere-ionosphere coupling model, with reasonable agreement. The potential exists to apply these detection techniques to real-time GPS TEC measurements, providing estimates of tsunami speed and amplitude that may be useful for early warning systems. COUP-02 Midlatitude ion temperature during sudden stratospheric warming events by Vicki Hsu Status of First Author: Student IN poster competition, Undergraduate Authors: Vicki W Hsu, Larisa P Goncharenko, Jeff P Thayer, Jiuhou Lei Abstract: Ionospheric variability impacts a variety of communication and navigation systems. Although the primary drivers of ionospheric variability, such as solar ionizing flux and geomagnetic activity, are relatively well understood, the effects of the lower atmosphere onto the ionosphere remain elusive. Due to the current deep solar minimum and the meteorological phenomena known as sudden stratospheric warming (SSW), new studies have shown promising results that shed light on the coupling of the ionosphere to processes from below. This study focuses on the SSW events that occurred in January 2008, 2009, and 2010, and presents the results obtained from the Millstone Hill incoherent scatter radar (42.6°N, Ionospheric variability impacts a variety of communication and navigation systems. Although the primary drivers of ionospheric variability, such as solar ionizing flux and geomagnetic activity, are relatively well understood, the effects of the lower atmosphere onto the ionosphere remain elusive. Due to the current deep solar minimum and the meteorological phenomena known as sudden stratospheric warming (SSW), new studies have shown promising results that shed light on the coupling of the ionosphere to processes from below. This study focuses on the SSW events that occurred in January 2008, 2009, and 2010, and presents the results obtained from the Millstone Hill incoherent scatter radar (42.6°N,