Laboratory geophysical fluid dynamics

地球在其流体核心中需要一个地球发电机来维持地磁场不受欧姆衰减的影响。在地球大约45亿年的历史中，这台发电机显然是由某种可靠的方式驱动的。传统上，人们一直认为地球的重力场作用于地核密度的差异，以保持地核流体通过对流而翻转。我们的研究提出了发电机的另一种持续能量来源，即来自太阳-太阳重力场，在那里产生潮汐和进动的相同力量可以导致核心的不稳定，从而驱动发电机。在过去的30年里，通过实验室实验观察到这种不稳定性，方法是通过使流体的边界变形或使边界进动，从而对包含在其中的旋转流体施加应变。当流体受到外部应变时，我们所称的旋转参数不稳定性不断增长和衰减。当我们在实验室研究这种不稳定性时，我们也在寻找古磁场的记录，以寻找我们实验室中看到的不稳定性的特征。在大约200万年的时间里，我们成功地完成了六次这样的搜索，随着我们将观测范围扩展到新的领域，我们正在改进对错误的分析。

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.