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

• Main Authors: Kloss, Clemens, Finlay, Christopher
• Format: Journal Article
• Language: English
• Published: 07-11-2019
• Subjects: Physics - Geophysics
• DOI: 10.48550/arxiv.1911.02879

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.