Time-dependent low latitude core flow and geomagnetic field acceleration pulses

Abstract

We present a new model of time-dependent flow at low latitudes in the Earth's core between 2000 and 2018, derived from magnetic field measurements made on board the {\it Swarm} and CHAMP satellites and at ground magnetic observatories. The model, called {\it CoreFlo-LL.1}, consists of a steady background flow without imposed symmetry plus a time-dependent flow that is dominated by geostrophic and quasi-geostrophic components but also allows weak departures from equatorial symmetry. We find that the equatorial region beneath the core-mantle boundary is a place of vigorous, localised, fluid motions; time-dependent flow focused at low latitudes close to the core surface is able to reproduce rapid field variations observed at non-polar latitudes at and above Earth's surface. Magnetic field acceleration pulses are produced by alternating bursts of non-zonal azimuthal flow acceleration in this region. Such acceleration sign changes can occur within a year or less, and when the structures involved are of large spatial scale they can give rise to geomagnetic jerks at the Earth's surface.

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Cited by in corpus (6)

• Rapid Variations of Earth's Core Magnetic Field
• Fast Quasi-Geostrophic Magneto-Coriolis Modes in the Earth's core
• Applications for CryoSat2 satellite magnetic data in studies of Earth's core field variations
• Acoustic and inertial modes in planetary-like rotating ellipsoids
• Secular variation signals in magnetic field gradient tensor elements derived from satellite-based geomagnetic virtual observatories
• The Nondipole Part of the Main Geomagnetic Field and the Large Scale Topographical Heterogeneities of the Core-Mantle Boundary