Signatures of high-latitude waves in observations of geomagnetic acceleration
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.
Citation Information
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 |