Astronomy & Space

The anisotropic inner core structure of the Earth is revealed by a study of the dipole geomagnetic field.

The Earth is shielded from cosmic radiation and the charged particles of solar wind by a geomagnetic field that is created within the planet and extends into space. The convection of charged molten iron fluids in the outer core of the Earth creates the magnetic field.

Earth’s inner core is inhomogeneous and anisotropic, as opposed to the convective, homogeneous outer core. The seismic velocity is 2–3 percent faster in the polar direction than in the equatorial direction.

Researchers led by professors The Earth’s anisotropic inner core structure is driven by the dipole geomagnetic field, according to Li Heping and He Yu from the Institute of Geochemistry of the Chinese Academy of Sciences (IGCAS).

On March 24, the study appeared in the journal Nature Communications.

“Aside from the geoscience implications, the unique physical properties of superionic effect are also critical for us to further understand the behaviors of superionic matter under extreme conditions in the interiors of exoplanets,”

 Dr. Sun Shichuan, first author of the study.

According to a study published in Nature last year, Earth’s inner core is made up of solid iron and liquid-like light elements (hydrogen, oxygen, and carbon), a state known as the “superionic state,” rather than being a typical solid.

In the current study, the researchers discovered that under high pressure and temperature conditions in the Earth’s inner core, hexagonal close-packed (hcp) Fe-H alloy exhibited both seismic anisotropy and H-ion diffusion anisotropy.

It was energetically advantageous for the Fe-H lattice to be aligned with the c-axis facing the direction of the external electric field. Due to this outcome, an electric field might be used to manipulate the Fe-H lattice’s alignment.

An interaction between the inner core and geomagnetic field was established, taking into account the distribution of the electric-magnetic field in the inner core. Significant seismic anisotropy was evident in the aligned texture driven by the geomagnetic field, which explains why the inner core’s anisotropic seismic velocities exist.

Dr. Dot He Yu, the study’s corresponding author, said, “It’s intriguing! The mobile hydrogens inside the Earth’s inner core may correlate with the geomagnetic field and thus form an anisotropic texture, which should give us a new perspective to understand the mysteries of the Earth’s inner core and the Earth’s magnetic field.

Dr. Sun Shichuan, the study’s first author, said that, “beyond the geoscience implications, the unique physical properties of the superionic effect are also vital for us to further understand the behaviors of superionic matter under the extreme conditions of exoplanets’ interiors.”.

More information: Shichuan Sun et al, Superionic effect and anisotropic texture in Earth’s inner core driven by geomagnetic field, Nature Communications (2023). DOI: 10.1038/s41467-023-37376-1

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