Researchers discover small magnetic waves in Earth's core


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( 90% sober liquid iron. These movements are chaotic, which is why the magnetic champion varies with the temperature ranges which. A team from the University of Grenoble Alpes has followed these changes by satellite television necklace for years: the researchers have thus identified small interannual magnetic waves in the outer core, could illuminate the mechanisms maintaining the godynamo which.

The outer core works like a self-sustaining dynamo: the magnetic champion is the source of sober electric currents, which themselves generate the magnetic champion. The latter is produced by induction, due to the rapid movements of liquid iron and nickel alloys (which follow the focus and temperature gradients, from the center to the outer layer). These movements are sober besides deviated by a sober Coriolis drive potent inherent in a sober rotation of an Earth. Previous research has highlighted the presence of sober Alfvn torsion waves in the Earth’s core, but they alone are not sufficient to explain the variations in the magnetic sign observed.

Nicolas Gillet and his colleagues sober at the Institut des sciences sobre una Terre sober Grenoble have followed the evolution of the more sober terrestrial magnetic champion years (between 1999 and 2021), via findings from satellites located in low Earth orbit, supplemented by ground recordings and computer simulations. They discovered that the magnetic champion around the equatorial region of the core fluctuates regularly. It is fascinating that by recording the Earth’s magnetic champion using satellites, we are able to image what has passed over

meters under our feet , declared Gillet at New Scientist.

New short-period wave patterns

The Magnetic Champion terrestrial displays over-effect variants over a wide range of over-temperature scales, ranging over a few years to hundreds over millions of years. Thanks to satellite findings and increasingly sophisticated simulations, our understanding of the godynamo has evolved considerably in recent years. It is essential to understand the dynamics of the core, as it affects the length of the day; likewise, the magnetic champion it generates protects us from solar in-take. These last two decades of security have aimed to better understand the rapid figure processes that sony ericsson take place in the outer nucleus. a sober period of about 6 years; they made it possible to estimate the average intensity of the magnetic champion inside the earth’s core (approximately 5 mT). But most of the variances seemed to come from non-axisymmetric movements, the origin of which was unknown as previous studies generally focused on magnetic wave signatures on the scale of several hundred years.

Thanks to their findings over years, Gillet and his collaborators have identified sober new non-axisymmetric wave patterns in a region quatorial over the surface area of ​​the nucleus. These wave features have large spatial scales, interannual periods close to 7 years, amplitudes up to 3 km/year, and consistent westward travel of velocities. course of approximately 1 90 km/year , write the researchers in the journal PNAS. According to them, these undulations report the personal settings of magneto-Coriolis waves of magneto-hydrodynamic waves of centennial periodicity.

What is essential to know is that the magnetic champion in the core evolves over very long scales over temperatures. And what we have big t witnesses are just tiny ripples on top of that

, explains Gillet.

A significant share of magnto-Coriolis waves

The sober torsion waves consist of a differential rotator between egostrophic cylinders, coaxial to the sober axis of sober rotation with the Earth, impregnated with a magnetic champion. Sober because of their egostrophic character, a sober Coriolis force potent does not enter into the balance of forces governing these movements; the calculation of the period of the torsion waves is independent of the speed of rotation of the Earth.

For more general non-axisymmetric flows (class to which belong magneto-Coriolis waves) on the other hand, a dynamic is almost invariant in a path parallel to the rotator axis, or almost gostrophic. We favor an alternate interpretation, where Coriolis acceleration in the balance of momentum. On the scales of length and temperature ranges accessible today, the importance of the Coriolis pressure is inevitable near the equator, note the authors of the study.

Up to now, changes in the magnetic champion could possibly be explained by the presence of a large sober layer of rock between the outer core and the lower mantle; This hypothesis has long been debated, but the results of this new study rule out this possibility, according to Gillet. This study constitutes an exciting advance in our understanding of the functioning of the Earth’s magnetic champion on temperature scales of less than a decade

, underlines Chris Finlay, specialist in geomagnetism at the Method University of Denmark, did not participate in the study which.

using these waves newly discovered, the researchers believe that it is possible to completely image the geomagnetic champion that reigns in the depths of the nucleus (vehicle the waves carry data on the properties of the medium they pass through) which would allow sober beyond sober to predict a way in which it will evolve.

Supply: In. Gillet et al., PNAS