Geophysics

The Core from Above

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Science  26 Oct 2012:
Vol. 338, Issue 6106, pp. 444
DOI: 10.1126/science.338.6106.444-d

Earth's core is split into a solid inner core and a fluid outer core. The convection and rotation of the outer core produce Earth's magnetic field and redistribute mass within the planet. Measured from orbiting satellites, variations in the magnetic field over time indicate changing outer core dynamics. Mass redistribution from fluid motion in the outer core should be detectable by gravity-sensing satellites, but surface processes such as the movement of water in the oceans and within river basins tend to dominate local gravity measurements. Mandea et al. reexamined global magnetic data to determine how the outer core changed over 8 years and correlated them with variations in gravitational data over the same time frame. Both sets of data show a distinct spatial feature centered under Africa, suggesting that core contributions to the gravity field are indeed measurable. A physical explanation for this feature may be related to density heterogeneity or interactions between the core and overlying mantle; however, more data collected from ongoing and future high-resolution satellites are needed to better understand the short-term dynamics of the outer core.

Proc. Natl. Acad. Sci. U.S.A. 109, 10.1073/pnas.1207346109 (2012).

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