Impact of inner-core size on the dipole field behaviour of numerical dynamo simulations
Impact of inner-core size on the dipole field behaviour of numerical dynamo simulations
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DOI：
10.1093/gji/ggz146
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发表时间：
2019-07-01
影响因子：
2.8
通讯作者：
Schwaiger, Tobias
中科院分区：
文献类型：
--
作者：
Lhuillier, Florian;Hulot, Gauthier;Schwaiger, Tobias
从一套56个化学驱动的发电机模拟，宽高比（内外核半径）范围从0.10到0.44，我们进行了第一个系统的研究，研究了内核尺寸对发电机反转行为的影响。我们表明，内核的增长导致了一个小内核状态（0.18）和一个大内核状态（> 0.26）之间的过渡，当产生的磁场是中等强度和偶极的时候，磁场是更强和更偶极的。在这个转变过程中，磁场变得更弱，偶极性也稍微减弱。当纵横比为0.20 ~ 0.22时，反转频率可能对对流强度的变化更为敏感，从而更容易达到高频。尽管除了内核的大小之外的其他因素可能有助于控制地球发电机的反转频率，但我们假设，在前寒武纪末和泥盆纪末之间地核发生的这种转变可能解释了在这段时间内出现的一段不寻常的持续时间，主要是反转过度活跃和复杂的低强度磁场。
From a suite of 56 chemically driven dynamo simulations with aspect ratio (inner to outer core radii) ranging from 0.10 to 0.44, we conduct the first systematic investigation of the impact of inner-core size on the reversing behaviour of dynamos. We show that the growth of the inner core leads to a transition between a small inner-core' regime ( 0.18), when the field produced is intermediately strong and dipolar, and a large inner-core' regime ( > 0.26), when the field is stronger and more dipolar. During that transition the field is weaker and slightly less dipolar. For aspect ratios 0.20 0.22, reversal frequencies may be more sensitive to changes in the vigour of the convection, allowing high frequencies to be reached much more easily. Although other factors than the size of the inner core likely contribute to controlling the reversal frequency of the Earth's dynamo, we hypothesize that the occurrence of such a transition for the Earth's core between the end of the Precambrian and the end of the Devonian could possibly account for the manifestation of an unusual long-lasting episode of predominantly reversal hyperactivity and complex low intensity fields during that still poorly documented period of time.