Laboratory geophysical fluid dynamics

地球的流体核心需要一个地球发电机来维持地磁场，防止欧姆衰减。在地球45亿年历史的大部分时间里，这个发电机显然是由一些可靠的手段驱动的。传统上，人们认为地球的重力场作用于地核的密度差异，以保持地核流体通过对流而翻转。我们的研究为发电机提出了另一种持续的能量来源，它来自月球-太阳引力场，在那里，产生潮汐和岁差的相同力量可能导致核心的不稳定，从而驱动发电机。过去30年的实验室实验已经观察到这种不稳定性，通过使其边界变形或导致该边界进动来对所包含的旋转流体施加应变。当流体受到外部应变时，我们所说的旋转参数不稳定性不断增长和衰减。当我们在实验室中研究这种不稳定性时，我们也在搜索古磁场的记录，以寻找我们实验室中看到的不稳定性的特征。在成功完成了大约200万年的六次这样的搜索之后，我们正在改进对错误的分析，因为我们将观测扩展到了新的领域。

Earth requires a geodynamo in its fluid core to maintain the geomagnetic field against ohmic decay. This dynamo has apparently been driven by some reliable means over most of Earth's history of some 4500 million years. Traditionally it has been thought that Earth's gravity field acts on differences in the core's density to keep the core fluid overturning by convection. Our research proposes another type of continuing source of energy for the dynamo that comes from the Luni-Solar gravity field, where the same forces that produce tides and precession can lead to instability in the core and hence drive the dynamo. Laboratory experiments for the last 3 decades have observed this instability by imposing a strain on a contained rotating fluid by either deforming its boundary or causing that boundary to precess. What we have termed a rotating parametric instability continually grows and decays while the fluid is subjected to external straining. While we are studying this instability in the laboratory we are also searching records of the paleomagnetic field for a signature of the instability seen in our laboratory. After successfully completing six such searches over some 2 million years, we are improving our analysis of errors as we extend our observations to new areas.