A doughnut-shaped structure beneath Earth’s surface provides clues to the planet’s magnetic field

Amazing stuff!

"... The doughnut-shaped structure sits within the outer core. It is parallel to the equator and is found only at lower latitudes. ...

“We don’t know the exact thickness of the doughnut, but we inferred that it reaches a few hundred kilometres beneath the core-mantle boundary,” ...

But unlike other research, which focuses on the first hour of seismic wave signals, the ANU-led study looked at waveforms many hours after the earthquake. ...

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From the abstract:

"Thermochemical inhomogeneities in the Earth’s outer core that enhance our understanding of the geodynamo have been elusive. Seismic constraints on such inhomogeneities would provide clues on the amount and distribution of light elements in the core apart from iron and nickel. Here, we present evidence for a low-velocity volume within the outer core via the global coda correlation wavefield. Several key correlogram features with a unique sensitivity to the liquid core show variations with wave paths remarkably slower in the equatorial than polar planes. We constrain a torus structure at low latitudes with ~2% lower velocity than the surrounding liquid outer core via waveform modeling. We propose a thermochemical origin for such a low-velocity torus, providing important constraints on the dynamical processes of the Earth’s outer core."

A doughnut-shaped structure beneath Earth’s surface provides clues to the planet’s magnetic field "A newly discovered doughnut-shaped region thousands of kilometres beneath the surface of the Earth is helping scientists understand the dynamics of our planet’s magnetic field."

Seismic low-velocity equatorial torus in the Earth’s outer core: Evidence from the late–coda correlation wavefield (open access)

Fig. 6. Ray path of K* feature, schematic of the OC heterogeneity, and absolute PKIKP travel time residuals.