Geomagnetic dependence of ionospheric disturbances induced by tsunamigenic internal gravity waves



A series of ionospheric anomalies following the Sumatra tsunami has been recently reported in the literature. These anomalies show the signature in the ionosphere of tsunami-generated internal gravity waves (IGW) propagating in the neutral atmosphere over the ocean. All these anomalies, observed in the total electron content (TEC) measured by GPS or altimeters, show geographical heterogeneity in the perturbed TEC amplitude and suggest a dependence on geomagnetic latitude. This latitudinal dependence has been taken into account in the previous 3-D modelling used for the interpretation of the TEC Topex and Jason data. Here we present an accurate description of the ocean–atmosphere–ionosphere coupling method, and focus on the properties of the propagation of tsunamigenic IGW in the neutral atmosphere and their interaction with the ionospheric plasma. The analytical dependence on the geomagnetic field in the neutral–plasma coupling discussed in detail and quantitative modelling is used to describe the propagation of a simple tsunami wave at the global scale. What emphasize the role of geomagnetic field within the neutral–plasma coupling at the equatorial and mid-latitude regions.

The results, presented here in terms of electron density and TEC variations, show a strong geometric dependance involving the magnetic field inclination and the propagative direction of the tsunami. If the strongest electron density and TEC perturbations are located around −15°, 0° and 15° North, the structure and amplitude of the modelled perturbation changes in the two studied cases—south–north and north–south tsunami propagation.