The Earth’s core in motion like nothing you’ve seen before !

Press release published by CNRS / CNES the CNRS
The Earth’s core in motion
A shield that protects us from solar wind, the Earth’s magnetic field is used as a bearing for airplanes, spacecrafts and even deep-well drilling. A better understanding of the physics behind our planet’s magnetic field, shaped in the outer core 3,000 km beneath our feet is therefore essential.

Like many planets and most stars, Earth produces its own magnetic field, primarily through a dynamo effect caused by the movement of an electrically conducting fluid – in this case, a mix of melted iron and nickel. This ocean of liquid metal – the outer core – surrounds a kernel of solid metal (the inner core). Observations only inform us of phenomena occurring at the core’s surface, and lab experiments are difficult to carry out. So, researchers had to used digital modeling as an alternative.

Researchers from the ISTerre/ OSUG (UGA / CNRS, USMB, IRD,IFSTTAR) and IPGP recently conducted the most detailed digital simulations to date of these movements, of the magnetic field they produce, and of their variations over a few hundred years.

Left : the speed at which liquid metal moves in the core and on its surface (in blue : to the west ; in red : to the east). The large blue area on the surface of the outer core depicts a giant liquid metal tornado (1,200 km radius) at a pole, which disturbs the core and is linked to a powerful magnetic field. Right : the surface radial magnetic field (in purple : positive ; in green : negative) and its intensity in the inner core (black : non-existent ; yellow : maximum).
Credit : Nathanaël Schaeffer

The high-definition models reproduce a large number of observed phenomena (such as tornados at the Earth’s poles on the core’s surface – see illustration), and combine them with the core’s underlying dynamics. This modeling was made possible through significant optimization of computer code and the use of 16,000 processors in GENCI supercalculators to perform the necessary calculations.
The next step : extend this type of simulation to a geologic time scale to better understand geomagnetic reversal, which last occurred 780,000 years ago.


Source

Turbulent geodynamo simulations : a leap towards Earth’s core, Geophysical Journal International, 2017, Nathanael Schaeffer, Dominique Jault, Henri-Claude Nataf et Alexandre Fournier.
doi : 10.1093/gji/ggx265

Video

Temperature field in the equatorial plane of the Earth’s core from a high resolution numerical simulation
Changes in temperature in the outer core (in red : high temperature ; in blue : lower temperature) over a few hundred years. Temperature changes set the metal liquid in motion (hot plumes rise while cooled masses fall, like a pot of boiling water).
Credits : Nathanael Schaeffer
Video available here

Local scientific contact

- Nathanaël Schaeffer, ISTerre/OSUG (CNRS/Université Savoie Mont Blanc/IRD/Ifsttar/Université Grenoble Alpes) : nathanael.schaeffer[at]univ-grenoble-alpes.fr 04 76 63 52 62

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