Ionospheric seismology: a new perspective in Earth Observation

Philippe Lognonne ⁽¹⁾, Giovanni Occhipinti ⁽¹⁾, Alam Kherani⁽¹⁾, Raphael Garcia⁽²⁾, Francois Crespon ⁽³⁾, Eric Jeansou⁽³⁾ and David Mimoun⁽¹⁾

⁽¹⁾ Institut de Physique du Globe de Paris, 4 Avenue de Neptune, 94100 Saint Maur des Fosses, France
⁽²⁾ Observatoire Midi-Pyrenaes - Universite Toulouse 3, 14, ave E. Belin, 31400 Toulouse, France
⁽³⁾ NOVELTIS, 2, Avenue de la Europe, 31520 Ramonville Sainte-Agne, France

Abstract

Due to the coupling of the atmosphere with the Earth surface, seismic waves and tsunami oceanic waves generate atmospheric waves, which shake the ionosphere and can then be detected by different methods. We present here a review of the observations, of the theory and of the perspectives of this new research area in Earth Science. For the remote sensing of seismic waves, we show several observations, performed by ground based systems, such as Doppler HF, or by ground-space systems, such as GPS. In most cases, these observations are performed for large quakes with magnitude larger than 7. Typically, about 10 quakes with such or larger magnitude may occur per year. We show that the detection and imaging of the seismic wave provide usefull seismological informations and measurements compatible with the existing tomographic model of the upper mantle, for Rayleigh waves observations, or with the a priori radiation diagram of the seismic source, for body waves. We can therefore expect that these observations, in a near future, may complement the existing seismological data. For the remote sensing of tsunami, we focuse on the signals which have been observed for the Sumatra, December 26th, 2004 and the Peru, June 23, 2001 events. These waves, detected by the dual frequency altimeters onboard in the Jason-1 and Topex/Poseidon satellites for Sumatra and by GPS receivers in both cases, confirm that the ionosphere is affected by tsunamis and that the ionospheric signals can be used for tsunami monitoring. We present here the first comparison between synthetics ionospheric signals and the associated observations. We then detail, for both cases (i.e. seismic and tsunami), the coupling mechanisms. A special focus is given on the coupling mechanism between the atmosphere and the ionosphere which is presented by solving the hydromagnetic equations for three ions: O2+, NO+ and O+ and electrons, in order to obtain the perturbed density, electric and magnetic field We finally conclude with the perspective of this technique for possible tsunami warning and remote sensing seismology and present different concepts for performing real time and continuous monitoring of the ionosphere, either from space or from the ground.