"A new study published in Nature Geoscience by geophysicists Yi Yang and Xiadong Song of Peking University in Beijing explored the nature of movement of Earth’s inner core, largely made up of iron and molten liquids. They found the inner core’s movement recently reduced enough they consider it “paused,” all part of what “seems to be associated with a gradual turning back of the inner core as a part of an approximately seven-decade oscillation.”
https://www.popularmechanics.com/sci...pped-spinning/
"Researchers discovered the inner core in 1936, after studying how seismic waves from earthquakes travel through the planet. Changes in the speed of the waves revealed that the planet’s core, which is about 7,000 kilometres wide, consists of a solid centre, made mostly of iron, inside a shell of liquid iron and other elements. As iron from the outer core crystallizes on the surface of the inner core, it changes the density of the outer liquid, driving churning motions that maintain Earth’s magnetic field".
"Now, Yang and Song say that the inner core has halted its spin relative to the mantle. They studied earthquakes mostly from between 1995 and 2021, and found that the inner core’s super-rotation had stopped around 2009. They observed the change at various points around the globe, which the researchers say confirms it is a true planet-wide phenomenon related to core rotation, and not just a local change on the inner core’s surface".
https://www.nature.com/articles/d41586-023-00167-1