Traveling ionospheric disturbances propagating ahead of the Tohoku-Oki tsunami: a case study | INSTITUT DE PHYSIQUE DU GLOBE DE PARIS

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  Traveling ionospheric disturbances propagating ahead of the Tohoku-Oki tsunami: a case study

Type de publication:

Journal Article

Source:

GEOPHYSICAL JOURNAL INTERNATIONAL, Volume 204, Ticket 2, p.1158 (2016)

Résumé:

<p>We document two kinds of traveling ionospheric disturbances, namely, CTIDs (Co-tsunami-Traveling-Ionospheric-disturbances) and ATIDs (Ahead-of-Tsunami-Traveling-Ionospheric-disturbances) related to the Tohoku-Oki tsunami of 2011 March 11. They are referred to the disturbances that remain behind and ahead of the principal tsunami wave front, respectively. We first note their presence in a numerical experiment performed using a simulation code coupling the tsunami, atmosphere and ionosphere. This code uses the tsunami wavefield as an input and simulates acoustic-gravity waves (AGWs) in the atmosphere and TIDs, in the form of total electron content (TEC) disturbance, in the ionosphere. The simulated TEC reveals the excitation of CTIDs (at about 2 TECU) and ATIDs (at about 1 TECU), representing up to 5 per cent disturbance over the ambient electron density, and they arise from the dissipation of AGWs in the thermosphere. A novel outcome is that during the tsunami passage between similar to 6 degrees and 12 degrees of epicentral distance, strong ATIDs arrive similar to 20-60 min ahead of the tsunami wave front covering similar to 3 degrees-10 degrees of distance from the tsunami location. Simulation results are compared with the far-field observations using GNSS satellites and confirm that ATIDs are the first detected TEC maximum, occurring 20-60 min ahead of the tsunami arrival. Our simulation also confirms the presence of largest TEC maximum representing CTIDs, 10-20 min after the first tsunami wave. ATIDs reported in this study have characteristics that can be potentially used for the early warning of the tsunami.</p>