Laboratory geophysical fluid dynamics

点击翻译按钮获取中文摘要

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.