Signatures of High‐Latitude Waves in Observations of Geomagnetic Acceleration
Signatures of High‐Latitude Waves in Observations of Geomagnetic Acceleration
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DOI：
10.1029/2021gl094692
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发表时间：
2021-10
影响因子：
5.2
通讯作者：
Rodrigo Chi‐Durán;M. Avery;B. Buffett
中科院分区：
文献类型：
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作者：
Rodrigo Chi‐Durán;M. Avery;B. Buffett
地磁场的二阶时间导数模型揭示了高纬度地区的显著活动。交替的正负地磁加速度以超过地核中标称流体速度的速度向西传播。我们表明，波是一个可行的解释这些意见。磁Rossby波产生具有适当相速度的高纬度响应。然而，预测的空间复杂性与观测结果不一致。我们的首选解释涉及纬向MAC波。当地核顶部存在分层层时，这些波可以解释观测到的地磁场。所需层的厚度超过100公里，浮力频率与旋转频率相当。我们预计随着时间的推移，相速度逐渐减少，导致未来的传播方向的变化。
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.