Three-dimensional waveform modeling of ionospheric signature induced by the 2004 Sumatra tsunami

International audienceThe Sumatra, December 26th, 2004, tsunami produced internal gravity waves in the neutral atmosphere and large disturbances in the overlying ionospheric plasma. To corroborate the tsunamigenic hypothesis of these perturbations, we reproduce, with a 3D numerical modeling of the ocean-atmosphere-ionosphere coupling, the tsunami signature in the Total Electron Content (TEC) data measured by the Jason-1 and Topex/Poseidon satellite altimeters. The agreement between the observed and synthetic TEC shows that ionospheric remote sensing can provide new tools for offshore tsunami detection and monitorin

Three-dimensional numerical modeling of tsunami-related internal gravity waves in the Hawaiian atmosphere

The tremendous tsunami following the 2011 Tohoku Earthquake produced internal gravity waves (IGWs) in the neutral atmosphere and large disturbances in the. overlying ionospheric plasma while propagating through the Pacific ocean. To corroborate the tsunamigenic hypothesis of these perturbations, we use a 3D numerical modeling of the ocean-atmosphere coupling, to reproduce the tsunami signature observed in the airglow by the imager located in Hawaii and clearly showing the shape of the modeled IGW. The agreement between data and synthetics not only supports the interpretation of the tsunami-related-IGW behavior, but strongly shows that atmospheric and ionospheric remote sensing can provide new tools for oceanic monitoring and tsunami detection

Imaging and modeling the ionospheric airglow response over Hawaii to the tsunami generated by the Tohoku earthquake of 11 March 2011

Although only centimeters in amplitude over the open ocean, tsunamis can generate appreciable wave amplitudes in the upper atmosphere, including the naturally occurring chemiluminescent airglow layers, due to the exponential decrease in density with altitude. Here, we present the first observation of the airglow tsunami signature, resulting from the 11 March 2011 Tohoku earthquake off the eastern coast of Japan. These images are taken using a wide-angle camera system located at the top of the Haleakala Volcano on Maui, Hawaii. They are correlated with GPS measurements of the total electron content from Hawaii GPS stations and the Jason-1 satellite. We find waves propagating in the airglow layer from the direction of the earthquake epicenter with a velocity that matches that of the ocean tsunami. The first ionospheric signature precedes the modeled ocean tsunami generated by the main shock by approximately one hour. These results demonstrate the utility of monitoring the Earth's airglow layers for tsunami detection and early warning

Geomagnetic dependence of ionospheric disturbances induced by tsunamigenic internal gravity waves

International audienceA 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 ge-omagnetic 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

An Approximate Calculation of Max-Min Fair Throughputs for Non-Persistent Elastic Flows

The general problem we consider is the analysis of a model in which there are several routes in a network, on each route elastic flows arrive randomly according to some arrival process, and each flow transfers a finite volume of data sampled from some distribution. We are interested in computing a measure of average flow throughput on each route, for a given bandwidth sharing mechanism. Such models arise in problems of network dimensioning and traffic engineering. In this paper, we assume Poisson arrivals of file transfer requests on each route, the transfer volumes are fluid and arbitrarily distributed. At each instant the network shares the bandwidth among the ongoing flows according to the max-min fair bandwidth sharing mechanism, ie, instantaneous max-min fair (IMMF) sharing. The measure of performance we consider is the time average bandwidth obtained by flows on each route. We propose a heuristic algorithm for obtaining an approximation for this performance measure for arbitrary routes in an arbitrary network topology. Simulations with various network topologies are used to evaluate the proposal. In spite of its simplicity, we find that the approximation works quite well in a variety or topologies that we have studied