Propagation of tsunami-driven gravity waves into the thermosphereand ionosphere

摘要

Recent observations have revealed large F-region electron density perturbations(-100%) and total electron content (TEC) perturbations (-30%) that appear to becorrelated with tsunamis. The characteristic speed and horizontal wavelength of thedisturbances are -,200 m/s and ,400 km. We describe numerical simulations using ourspectral full-wave model (SFWM) of the upward propagation of a spectrum of gravitywaves forced by a tsunami, and the interaction of these waves with the F-region ionosphere.The SFWM describes the propagation of linear, steady-state acoustic-gravity waves in anonisothermal atmosphere with the inclusion of eddy and molecular diffusion of heat andmomentum, ion drag, Coriolis force, and height-dependent mean winds. The tsunami ismodeled as a deformation of our model lower boundary traveling at the shallow water wavespeed of 200 m/s with a maximum vertical displacement of 50 cm and described by amodified Airy function in the horizontal direction. The derived vertical velocity spectrum atthe surface describes the forcing at the lower boundary of the SFWM. A steady-state 1-Dionospheric perturbation model is used to calculate the electron density and TECperturbations. The molecular diffusion strongly damps the waves in the topside (>300-kmaltitude) ionosphere. In spite of this, the F-region response is large, with verticaldisplacements of —2 to 5 km and electron density perturbations of —100%. Mean windshave a profound effect on the ability of the waves to propagate into the F-region ionosphere.