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。
英文摘要：
In a recent paper (Phys. Rev. Lett. 94 (2005), 184506; physics/0411050) it was shown that a simple mean-field dynamo model with a spherically symmetric helical turbulence parameter alpha can exhibit a number of features which are typical for Earth's magnetic field reversals. In particular, the model produces asymmetric reversals, a positive correlation of field strength and interval length, and a bimodal field distribution. All these features are attributable to the magnetic field dynamics in the vicinity of an exceptional point of the spectrum of the non-selfadjoint dynamo operator. The negative slope of the growth rate curve between the nearby local maximum and the exceptional point makes the system unstable and drives it to the exceptional point and beyond into the oscillatory branch where the sign change happens. A weakness of this reversal model is the apparent necessity to fine-tune the magnetic Reynolds number and/or the radial profile of alpha. In the present paper, it is shown that this fine-tuning is not necessary in the case of higher supercriticality of the dynamo. Numerical examples and physical arguments are compiled to show that, with increasing magnetic Reynolds number, there is strong tendency for the exceptional point and the associated local maximum to move close to the zero growth rate line. Although exemplified again by the spherically symmetric alpha^2 dynamo model, the main idea of this ''self-tuning'' mechanism of saturated dynamos into a reversal-prone state seems well transferable to other dynamos. As a consequence, reversing dynamos might be much more typical and may occur much more frequently in nature than what could be expected from a purely kinematic perspective.
Magnetic reversals in a geodynamo model with a stably-stratified layer
Laboratoire de Physique de l’École normale supérieure, ENS, Université PSL, CNRS, Sorbonne Université, Université Paris Cité（巴黎高等师范学院物理实验室，ENS，巴黎文理研究大学，法国国家科学研究中心，索邦大学，巴黎西岱大学）；Institute Universitaire de France (IUF)（法国大学研究所）
