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Signatures of High-Latitude Waves in Observations of Geomagnetic Acceleration
Geophysical Research Letters ( IF 5.2 ) Pub Date : 2021-10-06 , DOI: 10.1029/2021gl094692
Rodrigo Chi‐Durán 1 , Margaret S. Avery 2 , Bruce A. Buffett 1
Affiliation  

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.

中文翻译:

地磁加速度观测中高纬度波的特征

地磁场的二次时间导数模型揭示了高纬度地区的显着活动。正负地磁加速度的交替补丁以超过核心中标称流体速度的速度向西传播。我们表明波浪是对这些观察结果的可行解释。磁性罗斯比波产生具有合适相速度的高纬度响应。然而,预测的空间复杂性与观察结果不兼容。我们首选的解释涉及带状 MAC 波。当核心顶部存在分层层时,这些波可以解释观察到的地磁场。所需层的厚度超过 100 公里,浮力频率与旋转频率相当。
更新日期:2021-10-17
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