Since about a billion years ago, the inner core has been growing to reach its present size as measured by seismologists. Cosmochemistry and again seismology tell us about the composition, mainly iron, of the liquid outer core and inner core. More recently, seismology also revealed that the inner core is anisotropic and that it possesses a highly heterogeneous layer at its surface. The inner core is also playing a key role in the geodynamo (self-sustained Earth’s magnetic field) not only because crystallization is a source for dynamo action through the release of light material but also because the inner core provides a path for the electric currents associated with the geomagnetic field.
Our project GRICO addresses the related questions of the inner core structure and crystallization at the expense of the liquid core. Grain size and texture are very much unknown and similarly is the nature of the solid/liquid interface. We intend to make progress along two complementary routes: seismic investigations of the inner core and solidification studies. The inner core is deep and far but one can expect to find out more about the size and structure of the heterogeneous surface layer. We also expect to gain a better knowledge of the interior of the inner core, in terms of its anisotropic elastic structure. Solidification studies will have experimental and modelling aspects, addressing the typical features of the inner core crystallization. Experimental solidification in a pressure gradient will be performed and modelled. Solidification with extremely slow growth rates will be studied. Ultrasonic probing of the experimental solid samples and of the growing interface will be compared to visual observation, thus establishing a connection between seismology and solidification structures.
Within a 3 years duration, our interdisciplinary project will bring together researchers from seismology, physics, materials engineering, geodynamo, fluid mechanics and applied mathematics. Modellers and experimenters are equally represented. This is not only providing the opportunity for the PhD students and Post-Docs in the project to gain complementary training but this is also a chance to make a big step in the understanding of the structure of the fascinating inner core at the centre of the Earth.
Dr. Thierry Alboussière (Project Leader)
CNRS, Observatoire de Grenoble, Laboratoire de Geophysique Interne et Tectonophysique, Université Joseph-Fourier, Grenoble, France
Dr. Daniel Brito
Observatoire de Grenoble, Saint Martin d’Hères, France
Dr. Sébastien Chevrot
Observatoire Midi Pyrénées, Toulouse, France
Professor Thierry Duffar
Institut National Polytechnique de Grenoble, Saint Martin d’Hères, France
Dr. Peter Guba
Univerzita Komenského, Bratislava, Slovakia
Dr. Michael Le Bars
Universités d’Aix-Marseille I et II, Marseille, France
Dr. Ludovic Margerin
Observatoire des Sciences de l’Univers de Grenoble, Saint Martin d’Hères, France
Prof. Michael Worster
University of Cambridge, Cambridge, UK
