Fast Quasi-Geostrophic Magneto-Coriolis Modes in the Earth's Core

Fast changes of Earth's magnetic field could be explained by inviscid and diffusion-less quasi-geostrophic (QG) Magneto-Coriolis modes. We present a hybrid QG model with columnar flows and three-dimensional magnetic fields and find modes with periods of a few years at parameters relevant to Earth's core. For the simple poloidal magnetic field that we consider here they show a localization of kinetic and magnetic energy in the equatorial region. This concentration of energy near the equator and the high frequency make them a plausible mechanism to explain similar features observed in recent geomagnetic field observations. Our model potentially opens a way to probe the otherwise inaccessible magnetic field structure in the Earth's outer core.

Automated summary

The study proposes a hybrid QG model to explain the fast changes in Earth's magnetic field, identifying modes with periods of a few years at parameters relevant to the Earth's core. It demonstrates a concentration of energy in the equatorial region for a simple poloidal magnetic field considered here. The high frequency and energy concentration near the equator make these modes a plausible mechanism for explaining similar features observed in recent geomagnetic field observations.