A simple 3-D numerical model of thermal convection in Earth's growing inner core: on the possibility of the formation of the degree-one structure with lateral viscosity variations
Department of Deep Earth Structure and Dynamics Research, Japan Agency for Marine-Earth Science and Technology (JAMSTEC), 2–15 Natsushima-cho, Yokosuka, Kanagawa 237-0061, Japan
Received: 04 Dec 2015 – Accepted for review: 06 Dec 2015 – Discussion started: 15 Dec 2015
Abstract. An east-west hemispherically asymmetric structure for Earth's inner core has been suggested by various seismological evidence, but its origin is not clearly understood. Here, to investigate the possibility of an "endogenic origin" for the degree-one thermal/mechanical structure of the inner core, I performed new numerical simulations of thermal convection in the growing inner core. A setup value that controls the viscosity contrast between the inner core boundary and the interior of the inner core, ΔηT, was taken as a free parameter. Results show that the degree-one structure only appeared for a limited range of ΔηT; such a scenario may be possible but is not considered probable for the real Earth. The degree-one structure may have been realized by an "exogenous factor" due to the planetary-scale thermal coupling among the lower mantle, the outer core, and the inner core, not by an endogenic factor due to the internal rheological heterogeneity.
Yoshida, M.: A simple 3-D numerical model of thermal convection in Earth's growing inner core: on the possibility of the formation of the degree-one structure with lateral viscosity variations, Solid Earth Discuss., 7, 3817-3841, doi:10.5194/sed-7-3817-2015, 2015.