逆转的性质和逆转的性质

geomagnetic field的极性反转成簇

The clustering of polarity reversals of the geomagnetic field

在自然界中，非齐次随机点过程的时间分布通常可以建模为具有可变速率的更新泊松过程的实现。在这里，我们调查的经典例子之一，即时间分布的极性反转的地磁场。尽管常用的基本假设，我们表明，这一过程强烈偏离泊松统计，这种失败的起源源于时间聚类的存在。我们发现，一个利维统计是能够重现古地磁数据，从而表明存在的长期相关性的基础发电机过程。

地球磁场反转的范例模型

A paradigmatic model of Earth's magnetic field reversals

地球磁场的不规则极性反转在过去的几十年里引起了人们的极大兴趣。尽管最近对地球发电机的数值模拟显示了很好的极性过渡，但逆转的原因和基本机制还远未被理解。使用一个典型的平均场发电机模型与球对称的螺旋湍流参数α，我们属性的反转的基本特征的磁场动力学在附近的一个例外点的非自伴发电机运营商的频谱。在这种特殊的（分支）点的平方根类型的两个真正的特征值合并，并继续作为一个复杂的共轭对的特征值。特别着重于数值计算的时间序列与古地磁观测的比较。结果表明，所考虑的发电机模型具有高的超临界性可以解释所观察到的时间尺度和不对称形状的反转与缓慢的衰减和快速的字段恢复。

Can one use Earth's magnetic axial dipole field intensity to predict reversals?

We study predictions of reversals of Earth's axial magnetic dipole field that are based solely on the dipole's intensity. The prediction strategy is, roughly, that once the dipole intensity drops below a threshold, then the field will continue to decrease and a reversal (or a major excursion) will occur. We first present a rigorous definition of an intensity threshold-based prediction strategy and then describe a mathematical and numerical framework to investigate its validity and robustness in view of the data being limited. We apply threshold-based predictions to a hierarchy of numerical mod…

Does the Planetary Dynamo Go Cycling On? Re-examining the Evidence for Cycles in Magnetic Reversal Rate

The record of reversals of the geomagnetic field has played an integral role in the development of plate tectonic theory. Statistical analyses of the reversal record are aimed at detailing patterns and linking those patterns to core-mantle processes. The geomagnetic polarity timescale is a dynamic record and new paleomagnetic and geochronologic data provide additional detail. In this paper, we examine the periodicity revealed in the reversal record back to 375 million years ago (Ma) using Fourier analysis. Four significant peaks were found in the reversal power spectra within the 16-40-million…

The probabilistic structure of the geodynamo

One of the most intriguing features of Earth's axial magnetic dipole field, well-known from the geological record, is its occasional and unpredictable reversal of polarity. Understanding the phenomenon is rendered very difficult by the highly non-linear nature of the underlying magnetohydrodynamic problem. Numerical simulations of the liquid outer core, where regeneration occurs, are only able to model conditions that are far from Earth-like. On the analytical front, the situation is not much better; basic calculations, such as relating the average rate of reversals to various core parameters,…

莱索托玄武岩（南部非洲）侏罗纪地磁极性倒转的再认识

Revisiting the Jurassic Geomagnetic Reversal recorded in the Lesotho Basalt (Southern Africa)

我们进行了详细的和连续的古地磁采样的逆转到正常的地磁过渡记录的莱索托玄武岩（183 - 1马）的基地附近的约60个连续的流动单位。在交变磁场或热清洗之后，剩磁的方向通常很好地聚集在流动单元内。相反，样品的热不稳定性不允许获得可靠的古强度测定。由于火山活动的间隙，证实了风成沉积物和一个大的角度距离的流动的磁场方向之间的基础上或覆盖这些存款的地磁过渡是不完整的记录。跃迁路径与van Zijl等人（1962）的先驱工作中报道的明显不同。最过渡的地磁极出现在火山活动中断之后。一旦大陆在180 Ma前的相对位置被替换，后裂孔VGP集群在俄罗斯。然而，从该集群中发现了两个连续的反弹，VGP多次到达东亚海岸。因此，VGP路径并不局限于古经度。当磁场偏离正常或反转方向时，磁化强度降低，表明在反转期间磁场幅度降低达到80- 90%。我们的结论是，虽然反转是一个偶极子的弱得多的时刻比平均存在于新生代的时间，反转地球发电机的特征似乎基本相似。

Abrupt global events in the Earth's history: a physics perspective

The timeline of the Earth's history reveals quasi-periodicity of the geological record over the last 542 Myr, on timescales close, in the order of magnitude, to 1 Myr. What is the origin of this quasi-periodicity? What is the nature of the global events that define the boundaries of the geological time scale? I propose that a single mechanism is responsible for all three types of such events: mass extinctions, geomagnetic polarity reversals, and sea-level fluctuations. The mechanism is fast, and involves a significant energy release. The mechanism is unlikely to have astronomical causes, both …

为什么发电机容易逆转

Why dynamos are prone to reversals

在最近的一篇论文中（Phys. Rev. Lett. 94（2005），184506; physics/0411050）表明，具有球对称螺旋湍流参数α的简单平均场发电机模型可以表现出对于地球的磁场反转典型的许多特征。特别是，该模型产生不对称的反转，场强和间隔长度的正相关性，和双峰场分布。所有这些功能是归因于磁场动力学的非自伴发电机运营商的频谱的一个例外点附近。增长率曲线的负斜率附近的局部最大值和异常点之间的系统不稳定，并驱动它的异常点，并超过进入振荡分支的符号发生变化。这种反转模型的一个弱点是明显的必要性，微调的磁雷诺数和/或径向分布的α。在本文中，它表明，这种微调是没有必要的情况下，更高的超临界发电机。数值例子和物理参数的编译表明，随着磁雷诺数的增加，有强烈的趋势，异常点和相关的局部最大值移近零增长率线。尽管球对称α ^2发电机模型再次证明了这一点，但饱和发电机进入易逆转状态的“自调谐”机制的主要思想似乎可以很好地转移到其他发电机上。因此，反向发电机可能是更典型的，可能会发生得更频繁的性质比什么可以预期从纯粹的运动学的角度。