But what does the core do at the center of the Earth? Far from following the overall movement of other earth's shells, it appears to be animated by its own dynamics. A new study shows that not only does it rotate around itself at a different speed, but it is also animated by its own oscillation around its axis of rotation.
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The earth rotates on its axis and with it all the geological shells of which it consists. However, it appears that the rotation of these different layers is not completely synchronized. Previous studies have actually shown that the inner core rotates at a different speed than the outer shells. A differential movement that is involved in the creation of the earth's magnetic field.
A core that does what it wants!
A new study shows that the inner core also vibrates. In other words, the solid iron nucleus that occupies the center of the Earth behaves a little like a spinning top about to come to a stop. Researchers have just confirmed that the inner core periodically oscillates around its axis of rotation, following cycles lasting about 8.5 years. The results were published in the journal Nature Communications.
Additional constraints on the dynamics of the inner core and its structure
This 8.5-year signal had previously been discovered during studies of the movement of the poles, the periodic motion of the Earth's rotation axis and fluctuations in day length. These data suggest that the inner core was driven by its own vibration, different from that of the Earth's mantle. The researchers thus determined a shift in the rotation axes between these two earth shells by less than 1°. These results also make it possible to identify density heterogeneity within the inner core itself, which imposes significant constraints on seed stratification. It therefore appears that the Northern Hemisphere's inner core is denser than the other regions.