Earth's magnetic field is probably not reversing
Earth's magnetic field is probably not reversing
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DOI：
10.1073/pnas.1722110115
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发表时间：
2018-05-15
影响因子：
11.1
通讯作者：
Gunnarson, Sydney
中科院分区：
文献类型：
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作者：
Brown, Maxwell;Korte, Monika;Gunnarson, Sydney
至少从1840年开始，地磁场以每世纪5%的速度衰减，间接观测表明自1600年甚至更早以来就有衰减。这导致了地磁场可能正在发生逆转或偏移的断言。我们已经推导出一个跨越30-50 ka的地磁场模型，用于研究最近两次漂移的行为：Laschamp湖和Mono湖，分别集中在41和34 ka。在这里，我们表明，既不漂移演示场的演变类似于当前的地磁场的变化。在较早的时候，集中在49和46 ka，该领域是可比的，今天的领域，与今天的南大西洋异常（SAA）的强度结构相似，但是，这些SAA类领域发展成一个偏移或逆转。这表明，目前减弱的磁场也将恢复，而不会发生极端事件，如偏移或逆转。在46 ka的SAA-样的场结构似乎是coeval与公布的地磁调制铍和氯核素生产的增加，尽管全球偶极场在我们的模型中没有显着减弱在这段时间。这种一致性表明，宇宙成因核素的产生与地磁场之间的关系比通常假设的更为复杂。
The geomagnetic field has been decaying at a rate of similar to 5% per century from at least 1840, with indirect observations suggesting a decay since 1600 or even earlier. This has led to the assertion that the geomagnetic field may be undergoing a reversal or an excursion. We have derived a model of the geomagnetic field spanning 30-50 ka, constructed to study the behavior of the two most recent excursions: the Laschamp and Mono Lake, centered at 41 and 34 ka, respectively. Here, we show that neither excursion demonstrates field evolution similar to current changes in the geomagnetic field. At earlier times, centered at 49 and 46 ka, the field is comparable to today's field, with an intensity structure similar to today's South Atlantic Anomaly (SAA); however, neither of these SAA-like fields develop into an excursion or reversal. This suggests that the current weakened field will also recover without an extreme event such as an excursion or reversal. The SAA-like field structure at 46 ka appears to be coeval with published increases in geomagnetically modulated beryllium and chlorine nuclide production, despite the global dipole field not weakening significantly in our model during this time. This agreement suggests a greater complexity in the relationship between cosmogenic nuclide production and the geomagnetic field than is commonly assumed.