High‐Latitude Westward Jets in the Earth's Outer Core Due to Small‐Scale Convection

The general circulation of the Earth's outer core is driven by small‐scale convection. A model based on the dynamics of individual buoyant parcels is put forward to explain how the main features of the circulation are generated by the convection. The model predicts a distribution of buoyancy in the core such that the fluid is lighter/warmer at the poles and heavier/colder at the equator. Zonal velocity as a function of latitude is predicted by the model and compared with the previous observational data inferred from the variations of the Earth's magnetic field. The model demonstrates that the westward jets observed at the co‐latitude of approximately 210 are in a geostrophic balance with the dynamic pressure created by convecting parcels and with the excess hydrostatic pressure due to the redistribution of buoyancy in the meridional direction. Plain Language Summary Flow of liquid iron in the Earth's outer core is what creates the Earth's magnetic field. This flow is driven by convection where lighter/warmer fluid rises to the top and heavier/colder fluid sinks. In this work, a new theoretical model is offered. The model explains the recently discovered circumpolar jet flows which flow westward at high latitudes (Livermore et al., ). The model considers small buoyant blobs which rise or sink in the core. Interesting dynamics occur because of the misalignment between the buoyancy force on blobs and the rotation axis of the planet. Numerical simulations are often used to gain an understanding of the core flows and the geodynamo. However, the simulations are typically performed with viscosities that are much larger than that of the real fluid in the core and are unable to resolve realistically small‐scale convection. The theoretical model presented here provides a glimpse into an inviscid and nondiffusive dynamics. Key Points Dynamics of small‐scale buoyant parcels control general circulation in the Earth's outer core Magnitude of the westward jet at the tangent cylinder at colatitude of 210 is determined and compared with the previous observational data Buoyancy field inside the core exhibits warmer polar regions and colder equatorial regions