Tsunami monitoring using airglow imaging systems

Abstract

Tsunamis generate internal gravity waves (IGWs) that propagate vertically into the atmosphere and can create detectable signatures in the ionosphere. These signatures have consistently been observed in the presence of a tsunami for over a decade in the total electron content and for over 5 years in the 630.0 nm airglow. Here, we provide a comprehensive overview on the utilization of airglow imaging systems for monitoring tsunamis. We develop the basic theory behind tsunami-ionospheric coupling from first principles and give special attention to the topic of tsunami-ionospheric coupling efficiency. This is followed by the presentation and analysis of a methodology for extracting wave parameters of tsunami-induced signatures appearing in airglow images. The methodology is applied to the 11 March 2011 Tohoku and 16 September 2015 Chile tsunamis as case studies. A previously developed geometric model that takes into account the assumed posture of tsunami-induced IGWs in the geomagnetic field and the observation geometry is shown to predict the region of the sky in which the observations were seen.