鞍结分岔附近的可激性：一种反转机制
Excitability in the vicinity of a saddle-node bifurcation: a mechanism for reversals
摘要：
我们提出了一个新的机制振荡或随机反转的磁场发生从一个固定的发电机状态。的基本成分是存在两个近临界发电机本征模式，一个稳定的和不稳定的，碰撞在鞍结分岔。在此分叉之上，产生有限振幅极限环。在分叉附近，即使是少量的湍流波动也足以产生磁场的随机反转。当两个竞争的本征模具有不同的对称性时，这种情况需要产生发电机的流的对称性破缺。这与VKS实验的观察结果非常一致。它还可以解释行星或恒星磁场的动力学，并可用于理解经常在湍流背景下发展的大规模流动的逆转。
英文摘要：
We present a new mechanism for oscillatory or random reversals of the magnetic field that occur from a stationary dynamo state. The basic ingredient is the existence of two nearly critical dynamo eigenmodes, a stable and an unstable one, that collide during a saddle-node bifurcation. Above this bifurcation, a finite amplitude limit cycle is generated. In the neighbourhood of the bifurcation, even a small amount of turbulent fluctuations is enough to generate random reversals of the magnetic field. When the two competing eigenmodes have different symmetries, this scenario requires a broken symmetry of the flow that generates the dynamo. This is in good agreement with the observations of the VKS experiment. It can also explain the dynamics of planetary or stellar magnetic fields and can be used to understand reversals of large scale flows that often develop on a turbulent background.
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