What produces the inner core's seismic anisotropy and hemispherical asymmetry?
In plain words
Seismic waves cross the inner core a few percent faster along Earth's axis than along the equator, and its eastern and western halves look different. The crystal alignment and process behind this are not known.
Precise statement
Compressional waves travel about 3 percent faster on polar than equatorial paths; velocity, attenuation and anisotropy differ between quasi-eastern and quasi-western hemispheres; an innermost inner core may have a distinct anisotropy axis. Identify the iron phase (hcp or bcc) and the texturing mechanism (solidification texture, Maxwell-stress deformation, translational convection, order-disorder in Fe-Si) that reproduces all three observations. An answer is a dynamical model whose predicted texture matches global travel-time and normal-mode data.
What would settle it
A deformation or solidification model with mineral-physics elastic constants that fits global body-wave and normal-mode anisotropy, including the hemispherical pattern.