Understanding 30 Myr of geomagnetic field variability: a case study from low latitude (Ethiopia)

地球磁场如何随时间变化，称为长期变化，有助于深入了解地球发电机的工作原理。然而，对于需要哪些可测量的量和观测它们的时间尺度，才能获得对长期变化的完整描述，仍然存在争议。我们对五种发电机模型的数值研究表明，至少需要50万年的时间和100个与时间无关的方向和强度数据来区分不同的发电机状态。我们现在希望通过对埃塞俄比亚过去30万年形成的四个厚（1000-2500米）火山流剖面进行取样来检验这些理论预测。我们的目标是通过研究方向的几何和色散以及场强的大小和色散来辨别长期变化是否在这一时期演变。之所以特别选择埃塞俄比亚，是因为每一段都有大量的流量（100亿美元），它们的可达性，以及它们在相对恒定的地理位置上的显著时间跨度。埃塞俄比亚的工作将由长期合作者Tesfaye Kidane教授推动。

How the Earth's magnetic field varies over time, called secular variation, lends insight into the workings of the geodynamo. However, it remains debated which measurable quantities and the timescales over which they should be observed, are required to obtain a complete description of secular variation. Our numerical study of five dynamo models suggests that at least a half million years of time with 100 time-independent directional and intensity data are needed to distinguish different dynamo regimes. We now wish to test these theoretical predictions by sampling four thick (1000-2500 m) sections of volcanic flows in Ethiopia that were emplaced over the past 30 Myr. We aim to discern whether secular variation evolved during this period by investigating the geometry and dispersion of directions as well as the magnitude and dispersion of field intensity. Ethiopia is specifically chosen due to the large number of flows (>100) at each section, their accessibility, and their significant time span at a relatively constant geographic locality. Work in Ethiopia will be facilitated with a long-term collaborator, Professor Tesfaye Kidane.