Signatures of High‐Latitude Waves in Observations of Geomagnetic Acceleration
Abstract 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...
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| Format: | Article |
| Language: | English |
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Wiley
2021-10-01
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| Series: | Geophysical Research Letters |
| Online Access: | https://doi.org/10.1029/2021GL094692 |
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| author | Rodrigo Chi‐Durán Margaret S. Avery Bruce A. Buffett |
| author_facet | Rodrigo Chi‐Durán Margaret S. Avery Bruce A. Buffett |
| author_sort | Rodrigo Chi‐Durán |
| collection | DOAJ |
| description | Abstract 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. |
| format | Article |
| id | doaj-art-81b06c2971ec4fc6975c7350defd26cf |
| institution | OA Journals |
| issn | 0094-8276 1944-8007 |
| language | English |
| publishDate | 2021-10-01 |
| publisher | Wiley |
| record_format | Article |
| series | Geophysical Research Letters |
| spelling | doaj-art-81b06c2971ec4fc6975c7350defd26cf2025-08-20T02:09:35ZengWileyGeophysical Research Letters0094-82761944-80072021-10-014820n/an/a10.1029/2021GL094692Signatures of High‐Latitude Waves in Observations of Geomagnetic AccelerationRodrigo Chi‐Durán0Margaret S. Avery1Bruce A. Buffett2Department of Earth and Planetary Science University of California, Berkeley Berkeley CA USAU.S. Geological Survey, Moffett Field Menlo Park CA USADepartment of Earth and Planetary Science University of California, Berkeley Berkeley CA USAAbstract 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.https://doi.org/10.1029/2021GL094692 |
| spellingShingle | Rodrigo Chi‐Durán Margaret S. Avery Bruce A. Buffett Signatures of High‐Latitude Waves in Observations of Geomagnetic Acceleration Geophysical Research Letters |
| title | Signatures of High‐Latitude Waves in Observations of Geomagnetic Acceleration |
| title_full | Signatures of High‐Latitude Waves in Observations of Geomagnetic Acceleration |
| title_fullStr | Signatures of High‐Latitude Waves in Observations of Geomagnetic Acceleration |
| title_full_unstemmed | Signatures of High‐Latitude Waves in Observations of Geomagnetic Acceleration |
| title_short | Signatures of High‐Latitude Waves in Observations of Geomagnetic Acceleration |
| title_sort | signatures of high latitude waves in observations of geomagnetic acceleration |
| url | https://doi.org/10.1029/2021GL094692 |
| work_keys_str_mv | AT rodrigochiduran signaturesofhighlatitudewavesinobservationsofgeomagneticacceleration AT margaretsavery signaturesofhighlatitudewavesinobservationsofgeomagneticacceleration AT bruceabuffett signaturesofhighlatitudewavesinobservationsofgeomagneticacceleration |