Reconstructions of the geomagnetic field on long time scales are important to understand the geodynamo processes in the Earth's core. The geomagnetic field exhibits a range of variations that vary from normal, dipole-dominated secular variation to geomagnetic excursions and reversals. These transitional events are associated with significant directional deviations and very low intensities. Here we present a new, global geomagnetic field model spanning the period 70–15 ka (GGFSS70) that includes three excursions: Norwegian-Greenland Sea, Laschamps, and Mono Lake/Auckland. The model is built from nine globally distributed, high-resolution, well-dated, sedimentary paleomagnetic records. The GGFSS70 indicates that the axial-dipole component changed sign for about 300 years in the middle of the Laschamps excursion (41.25–40.93 ka). The energy comparison at the Earth's surface reveals that the axial-dipole energy is always higher than the non-axial-dipole except over the Laschamps. In the other two excursions, the axial-dipole is reduced by about one order of magnitude for the Norwegian-Greenland Sea excursion and less for the Mono Lake/Auckland. At the core-mantle boundary, the large-scale non-axial-dipole power is comparable to the axial-dipole power, except over the excursions when the axial-dipole decreases, though less clearly for the Mono Lake/Auckland excursion. The axial dipole moment over the 15–70 ka varies from 0 to 8 × 10²² Am², with an average and standard deviation of 5.1 ± 1.5 × 10²²Am². The Laschamps excursion is associated with growth and poleward movement of reversed flux patches and reversed field in the tangent cylinder at the excursion midpoint, which is not the case for the other two excursions.

中文翻译：

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基于选定的古地磁沉积记录的 15-70 kyr 时期地磁场的全球演化和动力学

在长时间尺度上重建地磁场对于了解地核中的地球动力学过程非常重要。地磁场表现出一系列变化，从正常的偶极子主导的长期变化到地磁偏移和逆转。这些过渡事件与显着的方向偏差和非常低的强度有关。在这里，我们展示了一个跨越 70-15 ka (GGFSS70) 的新全球地磁场模型，其中包括三个远足：挪威-格陵兰海、拉尚和莫诺湖/奥克兰。该模型由九个全球分布的、高分辨率的、年代久远的沉积古地磁记录构建而成。GGFSS70 表明轴向偶极子分量在 Laschamps 偏移（41.25-40.93 ka）中间改变了大约 300 年的符号。地球表面的能量比较表明，轴向偶极子能量总是高于非轴向偶极子，除了拉尚。在其他两次远足中，挪威-格陵兰海远足的轴向偶极子减少了大约一个数量级，而莫诺湖/奥克兰的则减少了一个数量级。在地核-地幔边界处，大尺度非轴向偶极子功率与轴向偶极子功率相当，除了轴向偶极子减小时的偏移，但莫诺湖/奥克兰偏移不太清楚。15–70 ka 范围内的轴向偶极矩从 0 到 8 × 10 对于挪威 - 格陵兰海游览，轴向偶极子减少了大约一个数量级，而对于莫诺湖/奥克兰，则减少了一个数量级。在地核-地幔边界处，大尺度非轴向偶极子功率与轴向偶极子功率相当，除了轴向偶极子减小时的偏移，但莫诺湖/奥克兰偏移不太清楚。15–70 ka 范围内的轴向偶极矩从 0 到 8 × 10 对于挪威 - 格陵兰海游览，轴向偶极子减少了大约一个数量级，而对于莫诺湖/奥克兰，则减少了一个数量级。在地核-地幔边界处，大尺度非轴向偶极子功率与轴向偶极子功率相当，除了轴向偶极子减小时的偏移，但莫诺湖/奥克兰偏移不太清楚。15–70 ka 范围内的轴向偶极矩从 0 到 8 × 10²² Am ²，平均值和标准偏差为5.1 ± 1.5 × 10 ²² Am ²。Laschamps 偏移与偏移中点处的切线圆柱中的反向通量斑块和反向场的增长和向极移动有关，而其他两次偏移的情况并非如此。