Traveling ionospheric disturbances over the United States induced by gravity waves from the 2011 Tohoku tsunami and comparison with gravity wave dissipative theory

The 11 March 2011 Tohoku earthquake generated a massive tsunami off the Pacific coast of Japan, which launched intense atmospheric gravity waves (AGWs) in the atmosphere. Within the context of this study, the Tohoku tsunami event was unique in the sense that it enabled a rare, controlled experiment for investigating how AGWs are launched, propagate, and dissipate in relation to tsunamis. This tsunami was a long-lived, rapidly traveling source of a rich spectra of AGWs excited just above the ocean-atmosphere interface. In this paper we use GPS total electron content (TEC) data from the United States (U.S.) to look for these AGWs in the ionosphere via their signatures as traveling ionospheric disturbances (TIDs). We find a spectrum of TIDs in the TEC data propagating in the direction of the tsunami that last for several hours over the West Coast of the U.S. and as far inland as western Colorado. The observed TIDs have periods that range from 14 to 30 min, horizontal wavelengths that range from 150 and 400 km, and horizontal phase speeds that range from 180 to 260 m/s. We use reverse ray tracing to show that the Tohoku tsunami was likely the source of these TIDs. Using the networks of GPS receivers in the U.S., we map the tsunami-launched TIDs over the western U.S. and investigate the spectrum of gravity waves enabling an enhanced understanding/verification of the properties of AGWs as a function of the launch angle.