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

Abstract

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.

References in corpus (4)

• Time-dependent low latitude core flow and geomagnetic field acceleration pulses
• Hydromagnetic quasi-geostrophic modes in rapidly rotating planetary cores
• Inviscid instabilities in rotating ellipsoids on eccentric Kepler orbits
• Pressure torque of torsional Alfvén modes acting on an ellipsoidal mantle

Cited by in corpus (6)

• Rapid Variations of Earth's Core Magnetic Field
• The interplay of fast waves and slow convection in geodynamo simulations nearing Earth's core conditions
• Applications for CryoSat2 satellite magnetic data in studies of Earth's core field variations
• Secular variation signals in magnetic field gradient tensor elements derived from satellite-based geomagnetic virtual observatories
• Characterisation of hydromagnetic waves propagating over a steady, non-axisymmetric background magnetic field
• Two-dimensional ideal magnetohydrodynamic waves on a rotating sphere under a non-Malkus field: I. Continuous spectrum and its ray-theoretical interpretation