Superionic effect and anisotropic texture in Earth's inner core driven by geomagnetic field.

Area of Science:

• Solid Earth geophysics
• Materials science under extreme conditions
• Geodynamics

Background:

• Seismological data indicate Earth's inner core (IC) is heterogeneous and anisotropic.
• The mechanisms and driving forces behind the IC's complex texture and anisotropy remain poorly understood.
• Hydrogen in iron under IC conditions enters a superionic state, exhibiting high diffusivity.

Purpose of the Study:

• To investigate the role of hydrogen diffusion in iron under inner core conditions.
• To explain the observed seismic anisotropy in Earth's inner core.
• To explore the coupling between the inner core's structure and the geomagnetic field.

Main Methods:

• Computational modeling of hydrogen ion diffusion in a superionic iron-hydrogen alloy.
• Analysis of the energetic favorability of lattice alignment under external electric fields.
• Correlation of simulated anisotropic texture with seismological observations of inner core anisotropy.

Main Results:

• Hydrogen ion diffusion in superionic iron-hydrogen alloy is anisotropic, with the lowest energy barrier along the c-axis.
• An external electric field promotes the alignment of the iron-hydrogen lattice with the c-axis parallel to the field.
• The Earth's geomagnetic field can align the iron-hydrogen alloy, causing seismic anisotropy consistent with observations.

Conclusions:

• The anisotropic diffusion of hydrogen in iron under inner core conditions, driven by the geomagnetic field, explains the observed seismic anisotropy.
• This provides a mechanism linking the inner core's structure and texture to the geomagnetic field.
• Suggests a significant coupling between the solid inner core and the geodynamo.