Skip to main content
U.S. flag

An official website of the United States government

Signatures of high-latitude waves in observations of geomagnetic acceleration

January 1, 2023

Models for the second time-derivative of the geomagnetic field reveal prominent activity at high latitudes. Alternating patches of positive and negative geomagnetic acceleration propagate to the west at speeds that exceed nominal fluid velocities in the core. We show that waves are a viable interpretation of these observations. Magnetic Rossby waves produce a high-latitude response with suitable phase velocities. However, the spatial complexity of the prediction is not compatible with the observations. Our preferred interpretation involves zonal MAC waves. These waves can account for the observed geomagnetic field when a stratified layer exists at the top of the core. The required layer has a thickness in excess of 100 km and a buoyancy frequency comparable to the rotation frequency. We anticipate a gradual reduction in the phase velocity over time, leading to a future change in the propagation direction.

Publication Year 2023
Title Signatures of high-latitude waves in observations of geomagnetic acceleration
DOI 10.1029/2021GL094692
Authors Rodrigo Chi-Duran, Margaret Susan Avery, Bruce Buffett
Publication Type Article
Publication Subtype Journal Article
Series Title Geophysical Research Letters
Index ID 70248962
Record Source USGS Publications Warehouse
USGS Organization Geology, Minerals, Energy, and Geophysics Science Center