Off-center gravity induces large-scale flow patterns in spherical Rayleigh-B\'enard

TL;DR

This study uses numerical simulations to show that even small shifts in gravity center in spherical Rayleigh-Bénard convection significantly alter flow patterns, with implications for Earth's core dynamics.

Contribution

It demonstrates how gravity center offset influences large-scale flow structures without affecting heat flux, providing insights into Earth's core asymmetry.

Findings

Gravity center shift induces large-scale flow patterns.

Flow structures are sensitive to small gravity offsets.

Heat flux remains unaffected by flow reorganization.

Abstract

Inspired by the hemispherical asymmetry observed in the Earth's inner core, we perform direct numerical simulations to study the effect of the gravity center offset in spherical Rayleigh-B\'enard convection. We find that even a minimal shift of the gravity center has a pronounced influence on the flow structures. When the gravity center is shifted towards the South, the co-latitudinal buoyancy component creates an energetic jet on the Northern side of the inner sphere that is directed towards the outer sphere. As a result, a large-scale meridional circulation is formed. However, surprisingly, the global heat flux is not affected by the changes in the large-scale flow organization induced by the gravity center offset. Our results suggest that the hemispherical core asymmetry is key to model the flow phenomena in the Earth's outer core and mantle.